Chapter One
GALLERY 1
NEARLY AS NATURE INTENDED
An exhibition of some curious molecules in the
foods we eat
[] AZTEC DREAMS [] RHUBARB PIE [] THE COCA-COLA CONUNDRUM
[] RUST REMOVER [] THE CURSE OF THE CURE-ALL
[] THE WORST SMELL IN THE WORLD [] CHINESE MEDICINE
[] THE STATE OF THE HEART [] THOSE UNSPEAKABLE MOLECULES
There are scores of myths surrounding the things we eat: chocolateis almost addictive; Coca-Cola is just a concoction of chemicals;garlic wards off heart disease and cancer; an aspirin a day keeps thedoctor away. None of these statements is true, but they contain a germof truth. In this gallery we can inspect the portraits of some of thenatural and unnatural chemicals which a normal diet contains.
The pleasures of eating are sweet but fleeting, while the warningsabout food seem bitter and never-ending. The warnings we should heedare those of professional dietitians, the front-line troops who arefighting the war against poor nutrition and unbalanced diets. Whilethey help the people who are referred to them, the rest of us only heartheir advice second-hand, and even then we do not heed it--which mayexplain why one person in five is now classed as obese (33% or moreoverweight) in the USA, and one in ten in Britain.
Behind the front-line dietitians is a regiment of armchair foodcommanders who offer their advice to anyone who listens. Often it issoundly based, telling us how to lose weight and still be properlynourished, but a lot is rather unhelpful, merely condemning somepopular foods as `junk' without explaining why they are so (althoughthis term is generally taken to mean that they contain too much sugar,salt, saturated fats and additives). Examples of junk food arechocolate, colas, hamburgers and french fries. Sadly the healthyalternatives, such as raw celery, mineral water and lentils, lackappeal for many, and especially for children.
Alongside claims about junk food come more dire warnings about thechemicals that are present in other foods, and especially if these havebeen added merely to make food look and taste more tempting, or if theyare there as contaminants that come from pesticides and processing.Surprisingly, most food-related illness comes not from these, but frommicro-organisms such as bacteria and fungi, and we are most at riskwhen we eat food that has not been properly stored or prepared. Ideallyfood should be free of all dangerous impurities, be they bacteria,fungi or chemicals.
Nature also has its chemicals, and some of these we are ratherpartial to, such as phenylethylamine and caffeine. Others we try toavoid, such as oxalic and phosphoric acids, and yet others we shouldtake more of, such as salicylate and selenium. In this Gallery we willview a display of molecules that are there in the foods we eat, and allof them are perfectly natural, except one: phthalate (this comescourtesy of the plastics industry). The others are examples ofmolecules that make us feel better, those which can do us harm, andthose which can make us smell.
Three of the molecules are to be found in chocolate. No food provokesthe emotional responses of chocolate. To some is it the junk food andappears to be little more than a temptation of the devil. Why is it soirresistible? Most people love it, some cannot resist it, and a fewunfortunate people have to avoid it. Some people stuff themselves withit until they are sick, while others claim that a mere lick of chocolatewill trigger an allergic attack. The makers of chocolate confectioneryadvertise their products in a variety of ways. They emphasize itswholesomeness and nutritional value, and claim it is full of energy;they suggest you offer it as a gift to a loved one, or even eat it as away of rewarding and pampering yourself. Whatever its benefits, it hasits risks, and some people regard chocolate as junk because its sugarrots teeth, its fats damage the heart, its calories put on weight andits cocoa can trigger a migraine attack.
An analysis of chocolate buyers in the UK showed that most chocolateis bought by women, who account for around 40% of sales, whilechildren buy 35% and men 25%. It tops the list of difficult-to-resistfoods, and accounts for over half of all food cravings. Some women evenclaim to be chocoholics and say they find it impossible to resist,especially before their monthly period. Clearly for them, chocolate ismore than just a tasty food or a treat. Chantal Coady, author of thebook Chocolate, questions whether there really are such people aschocoholics. She writes: `Although chocolate contains many active chemicals,some of which mimic natural hormones, none of these is addictive.' She believesthat women turn to chocolate for consolation when they need a littlecomfort, and that what they seek is the intense sweetness associatedwith chocolate confectionery, as well as its luxurious taste andtexture in the mouth.
Chocolate is a fairly well-balanced food consisting of 8% protein,60% carbohydrate, and 30% fat, although this last component is at theupper limit of what is desirable. A normal 100 g (4 ounce) bar provides520 calories, but it also provides some essential minerals and vitamins:
Minerals Vitamins potassium 420 mg A 8 mcg chlorine 270 mg B1 0.1 mg phosphorus 240 mg B2 0.24 mg calcium 220 mg B3 1.6 mg sodium 120 mg E 0.5 mg magnesium 55 mg iron 1.6 mg copper 0.3 mg zinc 0.2 mg
We shall be viewing the dietary importance of minerals in anexhibition in the next Gallery. Looking at this list it is perhaps notsurprising that chocolate bars make excellent emergency rations forsoldiers and explorers, but there are a few things missing, likevitamins C and D, so it is far from being a complete food. It also hasa few other things which are not nutrients, such as phenylethylamine,oxalic acid and caffeine. These have no nutritive value, but they doaffect us, and two of them are abundant in other foods and drinks aswell. The first three portraits in the exhibition concern thesechemicals.
[] Portrait 1
Aztec dreams--phenylethylamine (PEA)
The only thing in chocolate which comes anywhere near having a feel-goodeffect on our brain is phenylethylamine (PEA). The Mayas ofMiddle America, who flourished in Mexico from AD250 to 900,discovered the effects of this when they discovered chocolate, whichthey took as a drink and which they reserved for the ruling elite. Bythe time the Spaniards arrived at the end of the fifteenth century, theAztecs were the dominant civilization and the economy was partly basedon cocoa beans--levies from conquered tribes had to be paid in this currency.Aztec nobles also reserved chocolate for themselves, regarding it as anaphrodisiac, and yet forbidding women to drink it. When cocoa beanswere taken back to Europe, chocolate's reputation as a love-stimulantsailed with them. This reputation grew: it was now drunk by both sexes,and in 1624, one author, Joan Roach, devoted a whole book to itscondemnation, referring to it with puritanical disapproval as a `violentinflamer of the passions.' In the eighteenth century the great lover,Casanova, proclaimed chocolate to be his preferred drink.
Cocoa beans are harvested from the cacoa tree, which grows best inwarm, moist climates and within 20 [degrees] latitude of the Equator.The world production of cocoa beans is two million tons a year, andthey are grown in Brazil and Mexico for the North American market, andin West Africa for the European market.
After cocoa pods are harvested, the beans are removed and left in thesun to ferment. This exposure turns them brown and converts some oftheir sugars first to alcohol and then to acetic acid, which we knowbest in the form of vinegar. The acetic acid kills the shoot andreleases other flavour molecules. Phenylethylamine (PEA) forms duringthis fermentation stage. The beans are then roasted to remove most ofthe acetic acid, and milled, which causes the cocoa fat to becomemolten. The extent of the grinding process determines the differentgrades of chocolate.
Today when we speak of chocolate, we think of a piece of chocolatecandy, but originally chocolate was a drink. The name is derived fromthe Aztec word xocalatl meaning bitter water, and it was served as arather scummy liquid mixed with cinnamon and cornmeal. Later, vanillaand sugar were added to make it sweeter and more palatable for Europeantastes.
Despite what Casanova thought, chocolate is not an aphrodisiac, butthere may be some truth in the idea that it affects the brain. Analystshave detected more than 300 chemicals in chocolate. Two of them are ofstimulants: caffeine, which will be dealt with later in this gallery;and theobromine, which is chemically similar and was named after thecocoa tree, whose botanical name Theobroma cacoa means `food of thegods'. Theobromine is also present in tea.
The most likely chemical in chocolate that might explain itsfeel-good effect is PEA, of which there can be up to 700 mg in a 100 gbar (0.7%). Most chocolate contains much less than this, and a moretypical amount would be 50-100 mg. In its pure state PEA is an oily liquidwith a fishlike smell, and it can be made in the laboratory from ammonia. (PEAhas the curious property of absorbing carbon dioxide from the air.) Whenpeople are injected with PEA, the level of glucose in their blood goesup and so does their blood pressure. These effects combine to produce afeeling of well-being and alertness. PEA may trigger the release ofdopamine, which is the brain chemical that makes us feel happy, inwhich case PEA would be acting in the same way as amphetamines suchas ecstasy. PEA and ecstasy molecules are roughly the same shape andsize, and this has led to the suggestion that they might work in thesame way, but scientific proof is lacking that they do.
Our own bodies produce tiny but detectable amounts of PEAnaturally, and it is formed from an essential dietary amino acid calledphenylalanine. The level of natural PEA varies and it increases when weare under stress. It is also higher than normal in schizophrenics andhyperactive children, but this is more likely to be a symptom of theseconditions rather than their cause.
Not everyone can cope with a sudden influx of PEA, which is whysome people are sensitive to chocolate, often suffering a violentheadache if they eat too much. This happens because the excess PEAconstricts the walls of blood vessels in the brain. The human body haslittle use for PEA and employs an enzyme, monoamine oxidase, to disposeof it. People whose bodies are intolerant of chocolate appear to havedifficulty making enough of the enzyme to prevent the PEA building upto levels that triggers migraines.
That PEA is addictive seems unlikely, but there is another reason whysome people deny themselves the enjoyment of chocolate. Its fat content,which is called cocoa butter, is primarily a saturated fat. In fact itis 60% saturated, the same as dairy cream, and should be viewedlikewise. However, in Dr Herve Robert's book, Les vertus therapeutiquesdu chocolat, it is claimed that cocoa butter, unlike cream, does notlead to raised blood cholesterol levels.
The fat in chocolate is rather special in another way. Normal fatsare a mixture of saturated and unsaturated fats which tend to softenand melt over a range of temperatures. This is not what we want tohappen with a bar of chocolate. Chocolate has literally to melt in themouth at a temperature of around 35 Celsius, just below the bodytemperature of 37 Celsius. This is why the best way to enjoy a bar ofchocolate is to let a piece of it rest on the tongue until it melts andreleases its rich flavour and aroma.
Cocoa butter itself can solidify in several different ways, and eachmelts at a different temperature. Only one form is right for solidchocolate, which explains why chocolate-making is still regarded as muchas an art as a science, and why careful cooling of the molten chocolate isnecessary to ensure that the correct form solidifies. If you keepchocolate too long it becomes covered with a greasy white bloom, whichmakes it look as if it has gone off. It hasn't: this is not a mould,but only another of the crystal forms of cocoa butter, and is perfectlyedible.
When chocolate was regarded as a hot drink, the chemistry of its fathardly mattered. Then in 1847, the Quaker confectioners, J.S. Fry &Sons, of Bristol, England, introduced a solid form that could be eatenas a sweet. They made it by pressing the molten chocolate in order tosqueeze out the cocoa butter, and then added this to more moltenchocolate. The result was plain chocolate with rather a strong flavour.Much more popular was milk chocolate, bars of which were first producedin 1876 by the Swiss chemist Henri Nestle. He added condensed milk,which made the product lighter in taste (and colour) and opened themarket to children. Other Quaker families--the Cadburys, the Rowntreesand the Hersheys--entered the chocolate business and went on toestablish equally large chocolate empires in the UK and the USA.
Since then chocolate has never looked back. Yet it is not without itshidden hazards, although these pose less of a threat than eating toomuch chocolate, especially if this leads to obesity.
[] Portrait 2
Rhubarb pie--oxalic acid
Chocolate also harbours oxalic acid, a dangerous chemical that cankill--but rarely does. We take in oxalic acid every day from a varietyof sources. It occurs in lots of foods in small amounts, and in a fewfoods in large amounts, cocoa having one of the largest with 500 mg per100 g. Green leaf vegetables have the most, such as Swiss chard with700 mg per 100 g, spinach with 600 mg, and rhubarb with 500 mg.Rhubarb, also known as pieplant in the USA, is popularly thought tohave dangerously high levels because this food has killed people.Perhaps less well appreciated is that beetroot (300 mg) and peanuts(150 mg) also have a lot of oxalic acid.
The average person consumes about 150 mg of oxalic acid a day, andin countries where tea is popular the level is generally higher becausea cup of tea provides 50 mg. A fatal dose of oxalic acid is around 1500mg. Could we reach a deadly dose during the course of a normal day? Andwhat effect do even the lower levels of oxalic acid have on us?
Rhubarb is less popular than it used to be, but it was once widely eatenstewed with sugar. It was famed for its laxative properties, and it worksbecause it stimulates our gut to reject the natural toxin, oxalic acid.A bowl of stewed rhubarb could provide us with a sizeable fraction ofthe toxic dose. To poison yourself by eating bars of milk chocolatewould be virtually impossible, no matter how chocoholic you felt,because these contain much less oxalic acid and you would be satiatedwith them before you reached even the laxative level.
Rhubarb became infamous in World War I when people ate its leavesas a vegetable, and some died through oxalic acid poisoning. The levelof oxalic acid in rhubarb leaves is much higher than in the plantstalks, but you are not at risk from eating those.
Rhubarb has long been known as a medicament. In AD 70 the Greekphysician and botanist Dioscorides recommended it for treating a varietyof conditions. This was European rhubarb, and was used until thetwelfth century, when a superior rhubarb appeared from the East. Therewas much speculation as to where it was grown. Most came from Chinaand it continued to be imported on a large scale as powdered root forhundreds of years.
Rhubarb root has been used in traditional Chinese medicine for morethan four thousand years. The Royal Society of Arts, Manufacturers andCommerce decided to promote the cultivation of the new rhubarb in theBritish Empire, and during the next 30 years it awarded several goldmedals to those who grew the best varieties. In 1784 the Swedishapothecary Carl Wilhelm Scheele detected oxalic acid (which he knew asacid of sorrel) in rhubarb roots, and showed that the amounts in theplant's leaves were too large for these to be edible. The oxalic acid isthought to be the plant's protection against cattle. In 1860 theVictorian best-seller, Mrs Beeton's Book of Household Management,reported that rhubarb was in every kitchen garden, and she gave recipesfor rhubarb pies, rhubarb jam and even rhubarb wine. The easiest way ofcooking it was to stew the chopped stalks with sugar. When aluminiumpans became popular, stewing rhubarb was discovered to have anotherbonus: it cleaned the pans beautifully. It did this because the oxalicacid dissolved off the top layer of metal, although the amount that wasremoved this way was so tiny it was no threat to health.
This affinity of oxalic acid for metals also explains another curiousanomaly, and is the reason why nutritionists refer to it as anantinutrient. Oxalic acid interferes with the essential minerals iron,magnesium and especially calcium. Earlier this century spinach wasadvocated as a rich source of iron, and indeed it has higher levels ofthis metal than most vegetables. For example spinach has 4 mg of ironper 100 g, compared to peas which have 2 mg, brussels sprouts 1 mg, andcabbage only 0.5 mg. Despite having more iron, the oxalic acid in spinachrenders 95% of this metal useless as a nutrient, and only 5% can beabsorbed by our body. The cartoon character Popeye attributed hisstrength to spinach, but he was sadly misinformed. By all means eatspinach as a vegetable, enjoy it, but expect very little from it excepta modest amount of vegetable protein and a little vitamin C.
Oxalic acid kills by lowering the calcium in our blood below acritical level. (The antidote is calcium gluconate.) Calcium isessential for keeping the blood at a constant level of acidity andviscosity, as well as for clotting and transporting phosphate aroundthe body. But even in non-lethal doses the effect of oxalic acid oncalcium is worrying, because it forms insoluble calcium oxalate,crystals of which can grow into painful stones in the bladder andkidneys. The development of these is more likely if our fluid intake islow. Doctors whose patients are prone to develop such stones put themon a low-oxalic acid diet, which excludes the foods we have beentalking about. Although such foods can be avoided, we cannot excludeoxalic acid entirely from the body because there are other sources. Forexample, surplus vitamin C, which the body cannot store, may be turnedinto oxalic acid, and a side-effect of taking massive doses of thisvitamin may also be kidney stones.
According to John Timbrell, a toxicologist at the London School ofPharmacy and author of Introduction to Toxicology, it is possible toget a fatal dose of oxalic acid in other ways. People who haveaccidentally or deliberately drunk ethylene glycol, which is used asantifreeze in cars, may die of oxalic acid poisoning because the bodyconverts ethylene glycol to oxalic acid.
Plant cells are known to make use of oxalic acid, but it has no rolein animal cells--or so it was once assumed. Recent research suggestsotherwise. Despite the apparent toxicity of oxalic acid, the body willtolerate surprisingly high levels of it, and research scientists inGermany discovered that human tissue contains more oxalic acid than waspreviously suspected. Dr Steffen Albrecht and co-workers at DresdenUniversity have challenged the view that oxalic acid is merely anunwanted end-product of metabolism. They have developed a sensitivemethod of analysis for oxalic acid, and can measure concentrations aslow as millionths of a gram (mcgs) per litre of blood. Their work hasrevealed markedly different levels of oxalic acid in the blood: plasma,the fluid part of the blood, has 400 mcg per litre while serum, theclear solution which separates from blood after the plasma has coagulated,has 1200 mcg. Some blood cells have 250 000 mcg, which sounds a lot butwhen converted to milligrams is only 25 mg per 100 g, which is lowcompared to the levels in some foods. Albrecht says the high levels ofoxalic acid point to its having an active role in human metabolism,although what that is remains unknown.
Oxalic acid is made commercially by treating either sugar with nitricacid or cellulose with sodium hydroxide. The acid is very soluble inwater--a litre will dissolve 150 g--and it forms a corrosive solution.Industrially it is used in tanning leather, dyeing cloth, cleaningmetals and for purifying oils and fats. The only guise in which itmight be found in the home is in stain-removers for iron-based stains,such as rust and ink from fountain-pens.
[] Portrait 3
The Coca-Cola conundrum--caffeine
Chocolate contains a little caffeine, but there are much richer sources,such as coffee, tea and cola. Most ingredients in colas have beencriticized at one time or another, and yet the young people of the worldcontinue to love them. But look at the label on a bottle or can and itappears that all you are drinking is a solution of chemicals infizzy water. Colas contain little that can be described as natural. Themain ingredients are sugar or an artificial sweetener, phosphoric acid,caffeine, and a blend of flavourings, which are supposed to be a secret.Once upon a time they were, and when Coca-Cola was first invented thiswas part of its attraction.
There is no denying that the secret formula of Coca-Cola has beenhighly successful: it has seduced the taste buds of billions of peoplearound the world. Nor should we be surprised, because it is arefreshing, pleasantly flavoured drink, and a can of ice-cold coke canreally quench your thirst on a hot summer's day. Not surprisingly, ithas many imitators.
The story of Coca-Cola began on 28 June 1887 in [Atlanta, Georgia,when a pharmacist, Dr John Pemberton, then 56 years old, was grantedthe trademark, Coca-Cola, for a drink he had invented. The time wasright for the new beverage because the city of Atlanta had just voted toban alcohol, so perhaps it was not surprising that Coca-Cola sold well.Pemberton's new drink continued to sell even after prohibition wasrepealed in the city later that year.
Pemberton placed an advertisement in the Atlanta Journal describinghis new drink as follows:
Delicious! Refreshing! Exhilarating! Invigorating! The new and
popular soda fountain drink contains the properties of the
wonderful coca plant and the famous cola nut.
And indeed the drink is still named after these ingredients--the cocaplant, which is the source of cocaine, and the cola nut, which is richin caffeine. I should hasten to add that neither of these plantsprovides ingredients for today's colas.
Pemberton had stumbled upon a recipe that was to become the world'sbest-selling soft drink. He kept the flavour ingredients a closelyguarded secret, and the Coca-Cola company claim that only the top twoexecutives in the company know what they are, and how they should beblended.
Most of the main ingredients of Coca-Cola have always been commonknowledge: sugar, caramel, caffeine, phosphoric acid, lime juice, andvanilla essence. Together these make a passable concoction and thecaramel, lime and vanilla are the dominant flavours. There never was anycocaine in Coca-Cola, although Pemberton, who was a regular user ofthis drug, may have experimented with it. Cocaine was certainly added tocertain tonic wines of the day: Queen Victoria herself was reputed to bevery partial to some of these. The cola extract was also dropped fromthe recipe early on, in preference to adding purified caffeinedirectly. The level of acidity of Coca-Cola, which was needed for itsrefreshing taste, was originally due to citric acid, which occurs incitrus fruits, but this ingredient was soon replaced with cheaperphosphoric acid.
Pemberton needed to make his new drink distinctive, and so heexperimented with other flavours in smaller amounts. Finally he found ablend that he liked and gave it the code name 7X. So carefully did theCoca-Cola company protect the secret of 7X over the years that it wasprepared to defy court orders rather than reveal it. In Indiamanufacturers are obliged by law to say what is in a drink, but in 1977the company decided to cease marketing Coca-Cola in India rather thanreveal its secret.
Over the years there have been several attempts to guess what 7Xconsists of. Its natural essences are present in only tiny amounts, soit was almost impossible to discover what these were by chemicalanalysis, because each essence consisted of numerous flavour chemicals.In 1983, William Poundstone, author of the book Big Secrets, printedhis list of what he thought was in 7X, which he said consisted oforange, lemon, nutmeg, cassia, coriander, neroli and lime. Cassia isalso known as Chinese cinnamon, and neroli is extracted from thebitter-orange flower. Poundstone had made quite a shrewd guess, as weshall see.
Modern analytical techniques will lay bare the intimate details ofany secret mixture, and so perhaps it was not unduly worrying forCoca-Cola when Mark Prendergast finally published the recipe for 7X inhis book For God, Country and Coca-Cola in 1993. He says he came acrossit in the tattered remains of one of Pemberton's laboratory notebooksin the company archives. The mysterious 7X was a blend of the oils oflemon (120 parts), orange (80), nutmeg (40), cinnamon (40), neroli (40)and coriander (20). Pemberton mixed these with alcohol and then left itto stand for 24 hours to give him his secret extract. Today there is noalcohol, but it may be that the use of that ingredient duringprohibition explains Pemberton's original need for secrecy.
It is still claimed by the Coca-Cola company that it is the sequencein which the ingredients of 7X are blended that is the key to producingthe 'real thing', and it may still be that only two executives of thecompany know this. There are people who say they can identify thedifferent colas that are available, but a discriminating palate forthis type of drink is never likely to be considered the mark of aconnoisseur. Colas are simply refreshing drinks that do no harm andkeep many people employed in making, distributing, selling andadvertising them. When you buy a can of cola, it hardly matters thatpackaging, promotion and profits account for 95% of what you spend. Youcan be under no illusion that you are buying something essential, and aglass of water is even better at quenching your thirst and costsvirtually nothing. What you are really buying is a solution ofcaffeine, and this can have an effect on you.
The amount of caffeine in a can of cola is 40 mg, the same as in acup of tea, and about half that in a cup of freshly ground coffee. Thesame volume of instant coffee provides 60 mg, and over the last 50years this has become the most popular way to take caffeine. Instantcoffee was first produced by the Swiss company Nestle in 1938, and soldas Nescafe (the Brazilian Institute for Coffee had shown that coffeecould be reduced to a soluble powder in 1930). Instant coffee reallycame into its own in World War II when it was widely used by US troops,and thereafter it became part of everyday living.
Young people may get their daily dose of caffeine from colas, butmost adults get it from coffee and tea. While flavour is the mostimportant part of these drinks, it is the caffeine that explains theirenduring popularity. Tea is mainly drunk in the countries in which itis grown, such as India, Sri Lanka, and especially China, but a fewcountries are large importers, such as Great Britain and Australia.Coffee, on the other hand, is mainly grown as a crop for export incountries like Brazil, Colombia, Indonesia and Kenya. Internationaltrade in coffee beans exceeds $7 billion a year, making them one of thetop four traded commodities (along with coal, grain and oil).
Worldwide consumption of caffeine is now estimated to be over120 000 tons per year, which works out at about 60 mg per person perday. Scandinavians have the largest caffeine intake, generally fromcoffee, with over 400 mg per day; the British consume around 300 mgper day, much of it as tea; and the Americans, long regarded as bigcoffee and cola drinkers, get a surprisingly low 200 mg per day.
A fatal dose of caffeine taken by mouth would be about 5000 mg, theamount in 80 cups of coffee or 120 cups of tea. When you take incaffeine your body mobilizes its defences to dispose of the invadingtoxin, which is how it sees this non-nutrient. It rids itself of theoffending molecule by plucking off carbon atoms, although at first thishas little effect, because it leads to new molecules, such astheophylline and paraxanthine, which are just as potent. However, theprocess continues and finally the product is xanthine, which the bodycan eliminate in the urine or put to other uses. All this explains whythe effects of caffeine in the body persist for around five hours.Curiously, cigarette smoking stimulates the liver to generate morecaffeine-destroying enzymes and for smokers the effects last aboutthree hours.
More than 60 plant species produce caffeine, and it is believed thatthis chemical probably protects them against attack by insects. Thecoffee bush is indigenous to Ethiopia and was cultivated there over athousand years ago. It reached Europe around AD 1600, probably viaTurkey where it got its name, kehveh. Tea has a much longer tradition,and was being drunk in China in 2500BC, but it too did not reach Europeuntil the seventeenth century. The cola, or kola, plant is an evergreentree of tropical Africa which produces glossy nuts with a high caffeinecontent. The way to release their caffeine was to chew them.
Caffeine is not only a pick-me-up: it also has medicinal benefits,and is used in painkillers, asthma treatments, and diet aids. Theserely on its effect of stimulating the metabolism and relaxing thebronchial nerves. Caffeine has long been used to increase physicalendurance. In Tibet, not only do Tibetans drink a lot of teathemselves, but they give their horses and mules large vessels of thedrink. Distances were once measured in the number of cups of tea deemednecessary for a journey: three cups of tea would give you enough `fuel'for around 8 kilometres.
Chemically, caffeine is a white powder which was first isolated in1820 by the German chemist Friedlieb Ferdinand Runge, but it was notuntil 1897 that its molecular structure was deduced. It can be made inthe laboratory, but the commercial market is supplied by the caffeine whichis produced as a by-product of decaffeinating coffee. Removing caffeinewithout affecting the taste of coffee is relatively simple, and involvesextracting it with liquefied carbon dioxide.
There are many popular myths about caffeine. It is accused of causingsleepless nights, indigestion and bad breath, and as if that werenot enough it has also been blamed for raising cholesterol levels inthose who drink a lot of it, and so putting them at risk from heartdisease. There was even a suggestion in the 1970s that it might causeliver cancer, but that scare turned out to be completely unfounded. Nordoes it cause insomnia, indigestion or heart disease, and this was theconclusion of 175 scientists from around the world who attendedthe International Caffeine Workshop which was held in Greece in1993. As more and more data have been collected and analysed, themany scares about caffeine have been shown to be little more than theartefacts of poorly designed epidemiological studies into people'seating habits.
Caffeine affects us in many ways. It is metabolised by the liver,which takes about 12 hours to remove 90% of any caffeine we haveconsumed. The first few times we have caffeine it raises our heart rateand blood pressure quite dramatically, but as we become regulardrinkers of colas, coffee and tea, our body stops reacting in this way.Because of these physiological effects it was not surprising thatcaffeine was thought to be a factor in some common diseases. A reportin 1973 suggested that the risk of thrombosis was doubled if a personconsumed 400 mg a day, equivalent to drinking five cups of freshcoffee. However, a study in 1990 on 45 000 men failed to find anyconnection between thrombosis and coffee drinking. A supposed link withheart disease was also shown to be wrong by a large survey in Scotland,where both men and women have a particularly high incidence of thiscondition. The researchers there questioned more than 10 000middle-aged men and women and could find no link between caffeineintake and heart disease.
Caffeine acts as a stimulant and its drinks are advertised to emphasizethis, so we are told that coffee wakes us up and colas refresh, whilea cup of tea revives. It works by boosting the brain's own stimulantdopamine, and this responds up to around four cups of coffee, after which extracups have no more effect on the level of this in the brain. Caffeine inexcess is popularly believed to keep us awake at night, but it probablydoes not have this effect on most people, unless they drink too much.There are those who metabolise caffeine only slowly, and they may sufferthis way. Despite earlier reports that we cannot become addicted tocaffeine, caffeine withdrawal symptoms now seem to be accepted, andthey are, in order of occurrence: headache, depression, fatigue,irritableness, nausea, vomiting.
In addition to its caffeine, tea may have hidden benefits in theform of three other chemicals it contains. These are salicylate,epicatechin gallate and epigallocatechin gallate. We shall look at theportrait of salicylate a little further along in this gallery. Theother two molecules are part of a group known as flavinoids, and arethought to protect the body against free radicals. These are highlydangerous natural chemicals which have a rogue electron, and it is thiswhich enables them to attack key components of the living cell such asDNA, thereby possibly causing cancer. It is their relentless attack onthe body which is thought to be the underlying cause of ageing.
Perhaps tea-drinking can help in the fight against free radicals. ADutch research team carried out a 15-year study on men aged 50 andover, and in 1996 reported their findings which showed that tea-drinkershad a much reduced incidence of stroke. They attributed this to theflavinoids capability of destroying free radicals. Other research hasshown that the tea flavinoids also protect against tumours, at least inanimals.
[] Portrait 4
Rust remover--phosphoric acid
The ingredient of colas which looks rather odd, and rather menacing, isphosphoric acid. Generally we are more familiar with this acid as theactive agent in rust-removers, and with its salts, which are calledphosphates, and are used in detergents. In the 1970s and 80s,phosphates became a dirty word, and were blamed for the pollution ofrivers and lakes, with detergents being fingered as the most importantsource. We will look a little closer at this issue in Gallery 6, wherethere is a portrait of phosphates.
People need phosphate in their diet as an essential nutrient to makeDNA, build their bones and form their membranes. It also is needed forthe chemical adenosine triphosphate (ATP), which plays a central rolein helping get the energy we need from food. Phosphate-containingmolecules also act as messengers, and govern calcium transport. Inaddition to these major roles phosphate has many minor uses in thebody. It might seem that such a key element could be in danger of beingin short supply in our diet, but this rarely happens because the bodyrecycles it very effectively and in any case we have an enormous store ofphosphate in our skeleton. The phosphoric acid in colas can be regardedas making a useful but minor contribution.
Sometimes the phosphoric acid in colas has found other uses.Motorists, motorcyclists and truck drivers in the 1950s and 60s usedcola to clean the chrome bumpers (fenders), grilles and headlights whichlavishly adorned their vehicles in the fashion of those times. Thephosphoric acid reacted chemically with the chrome to form a hardsurface layer of chromium phosphate which protected it. It alsodissolved any rust that formed and protected any of the underlyingsteel which had become exposed. Industrially phosphoric acid is stillused for this purpose, and all anti-rust paints rely on it.
There is nothing sinister about phosphoric acid or its salts. To saythat colas contain an industrial cleaner, as one book has claimed, isstrictly true, but this is no reason to not drink them. Any phosphatein our food becomes phosphoric acid in the acidic conditions of thestomach. Every living cell needs phosphoric acid to function and itmatters not where it comes from.
The phosphoric acid in colas presents no threat to health; indeed, wecould regard it as an essential mineral. Plants begin the process ofsupplying the food chain with phosphate by extracting it from the soil,and they store phosphate in their seeds as the chemical phytic acid.They use this store when they germinate so they can put down rootswithout needing to take in any phosphate from the environment. Althoughseeds are highly nutritious on account of the protein, carbohydrate,fats and minerals they contain, they provide us with little in the wayof phosphate because we cannot digest the phytic acid store since welack the enzymes to release its phosphoric acids. So the phytic acidpasses straight through us--not that we need it, because every plantand animal cell that we eat contains more than enough phosphate.
We get most of the phosphate in our diet from natural sources such asfish, meat, eggs and dairy products, and a little from unnatural sourcessuch as colas, processed cheese, cheese spreads, sausages and cookedmeats, to which it is added to improve texture and regulate acidity.
[] Portrait 5
The curse of the cure-all--dipropenyl disulfide
When is something simply a flavouring and when is it a medicine?Garlic is admired by many for having both these properties, and thechemical which is responsible is a simple molecule called dipropenyldisulfide. But can it really be a healing drug? And if it is, should itnot be subject to the same kinds of tests that all pharmaceutical drugsare exposed to, so that we know it works and that it is perfectly safe?
Of course you don't need to bother with such tests if the materialyou are testing is basically a food flavouring ingredient that has longbeen part of the human diet. Time has tested it for you, althoughsometimes Time can be proved wrong--witness the once popular herb,comfrey, long used in salads and to make comfrey tea. The sale ofcomfrey is now banned in Europe because of the harmful chemicals itcontains. So perhaps chemists are not being too finicky when theysuggest that everything that purports to be a healing drug should betested in the same way as pharmaceuticals. In other words we should putdipropenyl sulfide through a programme of tests on animals such as miceand rats, dogs and cats, and finally monkeys and humans. Of course itwould fail early on, because it has undesirable side-effects, the worstof which is to give the patient an advanced case of halitosis. Nocreature deserves to have this obnoxious material forced on them,except human volunteers. Nevertheless, it is perfectly natural, and itis the most popular of the so-called alternative medicines on saletoday. It is sold as garlic oil and is purchased by millions of peopleall over the world and taken in the form of capsules. In Germany it isthe best-selling over-the-counter drug. We can get used to garlic andeventually come to like it.
Garlic-growing is big business, as well as being an essential partof the domestic garden in many countries. The USA produces around 65 000tons a year, worth $180 million, and this is grown mainly in California,especially around the small town of Gilroy (pop. 33 500), at whoseannual garlic festival it is possible to consume garlic ice cream,garlic cheesecake and garlic scones. In Europe garlic tends to be usedin cooking, especially for casseroles and soups, or in salads, and allover the world garlic bread has become a popular way of enjoying it.
Garlic used in cookery loses much of its sting while adding piquancyto soups and savoury dishes. Uncooked garlic in salads can be enjoyableto the eater but not to those they come in contact with afterwards. Yetsome people prefer to eat it raw for health reasons, believing it iseffective in warding off cancer and cardiac disease. Those who eat itregularly may find their bad breath protects them against illnessbecause it keeps others at a distance. Many are even willing to take itdaily in large amounts as though it really was a medicinal drug--but itisn't.
The active ingredient in garlic, dipropenyl disulfide, has two sulfuratoms at its centre, and it is these which produce the odour that itsusers have to endure, along with their family and close friends. Any chemicalwe consume which has a lot of sulfur, such as garlic, onions and certainforms of protein, poses a slight social problem for us, if not for ourbody. One way to get rid of some of the sulfur is to turn it into theobnoxiously smelling molecule methyl mercaptan, which we can breatheout. This is the main cause of halitosis, and we shall look moreclosely at its portrait next.
A clove of garlic has almost no smell until it is cut or crushed, butwhen this happens an enzyme called allinase works on an amino acidcalled allin, and converts it to allicin which is the main constituentin garlic extract. This is the precursor of dipropenyldisulfide--basically the same molecule but with an oxygen atom bondedto one of the two sulfurs. Allicin easily loses its oxygen atom andreduces to the more volatile molecule dipropenyl disulfide. This is thecompound which gives garlic its odour.
Raw garlic will give you plenty of this disulfide, but cooking getsrid of it because it is volatile enough to evaporate during cooking.This is the reason you can safely eat a soup or stew that has lots ofgarlic in the recipe, and still enjoy a friendly tete-a-tete withsomeone. Some claim that eating parsley or lettuce with raw garlicactually neutralizes its odour, which may well be so, but the evidenceis not compelling, and in the end some of it will still be exhaled onthe breath.
Epidemiological studies in China and Italy reported that garliceaters had fewer gastric cancers, and a survey of 40 000 US womenappeared to show a link between garlic consumption and lower rates ofcolon cancer. However, when Elisabeth Dorant and colleagues at theUniversity of Limburg, Maastricht, fed laboratory animals fresh garlicor garlic extracts, they did not observe fewer cases of cancer,although they found tumours were slightly slower in growing in thoserats with the disease.
Garlic is known to lower blood cholesterol levels by 10%, if you eata clove a day, and so it might help prevent cardiovascular disease.However, the evidence that it does so is again less than convincing. In1994 Christopher Silagy of Flinders University, Adelaide, and AndrewNeil of Oxford University reviewed several tests of the effect ofgarlic on blood pressure. They concluded that it only helped those withslightly elevated blood pressure, and they could not recommend it asroutine clinical therapy.
Such scientific evidence will not impress those who are still convincedthat garlic harbours something rather remarkable, and they can point out thatgarlic has been used in medicine for hundreds of years. Garlic's supporterscan even validate their cure-all claims with a bit of chemistryby pointing out that allicin and dipropenyl disulfide are antioxidants,and as such are highly regarded because they can mop up peroxides in thebody, thereby preventing the formation of free radicals.
Whether garlic really is effective in warding off cancer and heartdisease is doubtful, but the plant is not without its uses. Indeed, itis essential at Halloween, when ghosts walk, witches dance, demonspounce and vampires feast. This is the time to get out the garlic,which is guaranteed to be 100% effective in warding off evil spirits.What probably deters them is the smell of methyl mercaptan on theirvictim's breath, and this molecule is the subject of our next portrait.
[] Portrait 6
The worst smell in the world--methyl mercaptan
There are official standards for acceptable levels of noxious smells,and methyl mercaptan heads the list. This molecule makes the newswherever it is emitted in large amounts, and sometimes it does sobecause it is used industrially, for example for making the insecticideDimethoate. When it was accidentally released from a factory inWaltham Abbey, England, the local residents were so sickened by itssmell that some rushed to hospital assuming they were being poisonedby a deadly pollutant. Others rang the local gas company. This is not assurprising as it seems, because compounds similar to methyl mercaptanare used to odourize natural gas, so that leaks are easy to detect.
Methyl mercaptan is also produced naturally from bacteria in theenvironment, and the shoreline near Edinburgh, Scotland, often exudesit, much to the distress of the residents of the select suburb whichoverlooks that beautiful stretch of water.
The methyl mercaptan we breathe out after eating garlic or taking agarlic capsule is produced in the body as we digest allicin. Bacteriaare also responsible for the methyl mercaptan we generate in our ownmouths and may breathe out continuously as bad breath. This is formedfrom our own body protein as it breaks down under bacterial attack. Wecan easily detect methyl mercaptan when someone speaks to us--humanscan detect it at levels of parts per billion in air--but, curiously,we cannot smell the gas we produce ourselves. In Japan, you can testyour own breath with an Oral Checker of which thousands have alreadybeen sold. Katunori Nakamura has patented his halitosis detector, whichis about the size of a powder compact and works on the principle that ametal oxide, like tin oxide, changes its electrical resistance when itabsorbs a gas like methyl mercaptan onto its surface.
Bad breath is caused by several molecules, such as hydrogen sulfideand dimethyl sulfide, but the main culprit is methyl mercaptan. Hydrogensulfide, the traditional stink of the chemistry laboratory, is much lesssmelly, and the same is true of dimethyl sulfide, which is part of thearoma of fresh coffee. Graham Embery of the University of Wales atCardiff researches the sulfur-containing molecules found in the mouthwhich arise as a result of the activity of bacteria. These break downthe protein residues and release methyl mercaptan from the amino acidscysteine and methionine. If the smell of methyl mercaptan is verystrong, it indicates gum disease. Methionine is essential for allliving things, and animal protein contains up to 4% of this amino acid;therefore bacteria are capable of releasing enough methyl mercaptan tomake the victim's breath smell vile.
Embery and Gunnar Rolla of the University of Norway in Oslo areauthors of the book Clinical and Biological Aspects of Dentifrices,which devotes a whole chapter to halitosis. Embery's advice to thosewho suspect that they exhale methyl mercaptan is to use a toothpastethat contains anti-plaque agents, such as zinc or tin salts. Thesemetals interfere with the enzymes in the bacteria which produce themethyl mercaptan. Traditionally, mouthwashes are supposed to curehalitosis, but they do little more than clean the mouth and disguisethe offending smell. The best known one, Listerine, consists of waterand alcohol, with benzoic acid and natural flavours, such as thymol andmenthol. A good rinse with a mouthwash will remove about half the oralbacteria. A more popular way to clean the mouth is to increase salivaflow by chewing gum.
Our feet can also harbour microbes that give off methyl mercaptan,especially if we provide them with a perfect environment of unwashedsocks and unventilated shoes. Staphylococci and aerobiccoryneform bacteria are to blame, and these flourish in the increasinglyalkaline conditions which are a feature of such socks and shoes. If you havesmelly feet, then the chemical answer is to insert into your shoesspecial charcoal-filled insoles, which have layers of carbon thatabsorb the methyl mercaptan. Since the amount of methyl mercaptan istiny, the insoles will go on working for weeks.
Methyl mercaptan is the simplest member of a series of compoundsin which there can be chains of up to 20 carbon atoms attached to asulfur atom. Methyl mercaptan has one carbon atom. Mercaptans withthree and four carbons are those we encounter when we smell a leak ofgas. A mercaptan with 18 carbons attached to a chain is used as a wax insilver polishes.
A major drawback in manufacturing and transporting methylmercaptan for industry is its low boiling point of 6 Celsius. Luckily,it can easily be turned into the chemically similar dimethyl disulfide(DMDS), a yellow liquid which boils at 110 Celsius. This consists oftwo methyl mercaptans joined through their sulfur atoms. It is onlyslightly less odorous, but is much safer to transport, and most is madeat Lacq in south-west France, where natural gas wells bring up largeamounts of hydrogen sulfide. This is reacted with methanol to formmethyl mercaptan and then converted to DMDS.
Methyl mercaptan is used industrially to make pesticides, andespecially for weedkillers for cereal crops like wheat, maize and rice.Its chief use in industry is to regenerate the catalysts used in therefining of petrol. Methyl mercaptan is also used to make methionine,an amino acid which may be deficient in the diet. Some animal feeds arenow fortified with methionine, thereby increasing the amount of this inthe animals' meat and milk.
[] Portrait 7
Chinese medicine--selenium
Merthyl mercaptan and dimethyl sulfide may be the worst smells wecome across in normal life, but there are even worse variants of thesemolecules; their selenium versions. Selenium is chemically very similarto sulfur, but when it replaces sulfur in a volatile molecule the smellintensifies dramatically. Research chemists who work with seleniumcompounds have to be very careful to avoid contact with them. Anythat gets on to the skin, or even on to clothing, is liable to beexpelled as a methyl compound by any micro-organism that is around. Ifyou accidentally ingest some, then your breath will smell appalling. Ifyou take too much selenium then you could even poison yourself.
Despite this unpleasantness, selenium is essential to many species,including humans. We need it only in microgram quantities, but even soevery cell of our body contains over a million atoms of selenium. Atsuch low levels it poses no threat to our social life.
It is difficult to measure how much selenium we take in, how muchwe excrete, and how much we really need. The daily intake variesbetween 6 and 200 mcg according to the type of food we eat. The averageWesterner takes in about 60 mcg per day, which is more than enough toprevent the symptoms of selenium deficiency--a mere 10 mcg may beall we need, provided we get it regularly. Some days our body may losemore selenium than it absorbs, but because the average adult holdsabout 15 000 mcg (or 15 mg) this does not pose a threat. A single doseof 5000 mcg (5 mg) would be dangerous, and 50 000 mcg (50 mg) wouldbe lethal for many humans. We store most of our selenium in ourskeleton, but the parts of the body with the highest levels of seleniumare hair, kidneys and testicles.
Most people get most of their selenium from wheat products such asbreakfast cereals and bread. The foods richest in selenium are:
* seafoods, such as tuna, cod and salmon
* offal, such as liver and kidney
* nuts, such as Brazil nuts, cashews and peanuts
* wheat germ, bran and Brewer's yeast.
All these have 30 mcg or more of selenium per 100 g of product,although in the case of wheat and meat products the level depends uponthe soil of the farm from which they came. The only people who mightjust be at risk of selenium deficiency are pregnant and breast-feedingwomen, and children--and only if they carefully avoided all the types offoods listed above. Essential though selenium is, we can have too much,and the recommended maximum daily intake is 450 mcg. Abovethis we risk selenium poisoning, the most obvious symptom of which isbad breath and body odour. The smell is caused by volatile methylselenium molecules which our body produces as it rids itself of theselenium it does not need.
Despite the smell, we would die without selenium. In 1975 it wasproved essential for humans when Yogesh Awasthi discovered it waspart of a human enzyme called glutathione peroxidase. In 1991 DietrichBehne in Berlin found selenium in a second enzyme, deiodinase, whichpromotes hormone production in the thyroid gland. If the amount ofselenium in our body is too low, then we appear to be at risk fromseveral conditions, such as anaemia, high blood pressure, infertility, cancer,arthritis, premature ageing, muscular dystrophy and multiple sclerosis.As yet there is no proof that a lack of selenium in the diet leads tothese conditions, and it is more likely that this element is having asecond-order effect, in other words it controls other components whichactually do the harm.
Selenium is known to protect us against the effects of other toxicmetals such as mercury, cadmium, arsenic and lead: for example, thedamage that cadmium can do to our reproductive organs and to a foetusis thought to be prevented by selenium. Tuna fish, which accumulatehigher-than-expected levels of mercury, are also thought to be protectedby selenium, and analysis shows that for every mercury atom in a tunathere is also an atom of selenium. This 1:1 ratio appears to be true forother marine mammals such as seals, and for men who work in mercurymines.
Most normal diets contain more than enough selenium, so there islittle need for people to take selenium supplements, although these areon sale in health foods shops and pharmacies. As a dietary supplement,selenium is taken in the form of sodium selenite, which is a whitecrystalline material that is soluble in water. The daily dose is 50 mcg.Selenium was first popularized as a dietary aid by Alan Lewis, whosebook Selenium: the Essential Trace Element You Might Not be GettingEnough Of was published in 1982. Lewis reported that selenium could beused to treat rheumatism, arthritis, heart disease and cancer, and thatit would even delay old age. While most of these claims appear fanciful,and are based mainly on anecdotal evidence, two at least are wellfounded: trials in China have shown that selenium does prevent certaintypes of heart condition, and that the body needs a certain level if itis to ward off cancer effectively.
The Chinese have long had a special interest in selenium becauselarge areas of that country have selenium-deficient soil, and thisaffects the health of the local population. Children in the Keshanregion were prone to a heart condition known as Keshan disease, whichis caused by a lack of selenium. This disease results in a swelling ofthe heart and kills half of those afflicted. A large-scale trial insouth China in 1974 involved 20 000 children, half of whom were givenselenium-containing tablets and half given a placebo. Of those on theplacebo, 106 developed Keshan disease and 55 died, while of those onthe selenium supplement only 17 got Keshan and one died.
Another test in China also found that selenium was beneficial inreducing cancer cases. Among the Chinese people living in the northcentral province of Linxian there is a high incidence of stomach cancer.The people there agreed to take part in a five-year project and 30 000middle-aged people were given different combinations of dietarysupplements such as vitamins A, [B.sub.2], C and E, zinc and selenium.The study showed a remarkable drop in cancer cases in the group takingvitamin E plus selenium.
Selenium was discovered in 1817 by Jons Jacob Berzelius atStockholm, Sweden. He named it after selene, the Greek word for theMoon, to match the name of the related element tellurium, which wasbased on the Latin tellus meaning Earth. He found it when heinvestigated a red-brown sediment which collected at the bottom of thechambers in which sulfuric acid was made. The element selenium isavailable either as a silvery metal or as a red powder. The mainproducing countries are Canada, the USA, Bolivia and Russia, and mostcomes from copper smelters and refiners. Copper sulfide ores have copperselenide as an impurity. The most important source of selenium is theslime which settles at the bottom of tanks when impure copper is refinedelectrolytically, and this sediment may contain up to 5% selenium. Thissource accounts for about 90% of selenium production. Each year about150 tons of selenium is recycled from industrial waste and reclaimedfrom old photocopying machines.
The metallic form of selenium has the curious property of generatingan electric current when light falls on its surface, and it is used inphotoelectric cells, light meters, solar cells and photocopiers. Theseelectronic uses account for about a third of all selenium production,and require high grade selenium of 99.99% purity. The second largestuser is the glass industry, where selenium goes into special glass suchas the bronze architectural glass which screens out the Sun's rays. Thethird main use is to make sodium selenite for animal feeds and foodsupplements. Selenium is also used in metal alloys, such as the leadplates used in storage batteries; in rectifiers to convert electriccurrent from a.c. to d.c.; and in anti-dandruff shampoos.
Selenium is rarer than silver, and one day mineral sources of theelement will be exhausted. Then we may have to harvest it by growingcrops like milk-vetch on high-selenium soils. This could yield as muchas 7 kg per hectare (3 kg per acre). The current world demand forselenium, of about 1500 tons per year, would require about 200 000hectares to be farmed this way. But as reserves of selenium in oredeposits amount to over 100 000 tons, it will be quite some time beforethis type of farming will be needed.
The effects of high-selenium soils have been known for a long time.Animals grazing on such pasture may suffer from the so-called `blindstaggers'. Marco Polo (1254-1324) wrote that the animals of Turkestanbehaved this way. The plant responsible for the staggers was probablyvetch, which can concentrate up to 1.4% of its weight as selenium. Thecowboys of the Wild West knew that this plant could affect their herds,and called it locoweed, from the Spanish word loco meaning insane.In 1934 the biochemist Orville Beath proved that the staggers werecaused by excess selenium in the diet. When the vetch had an offensivesmell, it was a sure indication that it had absorbed a high level ofselenium.
[] Portrait 8
The state of the heart--salicylates
In 1763 the Reverend Edmund Stone, an English parson living in theCotswolds, made an infusion of the bark of the white willow and gave thedrink to people in his village who had fever. Today we can only guess atwhat his parishioners were suffering from, but one suspects most ofthem probably had a mild virus infection, such as `flu. In any event,they clearly had high temperatures and the treatment was successful inbringing these down. We now know that it would have been effectivebecause Stone had given the villagers a solution that in the human bodywould produce salicylic acid, which is good at reducing high bodytemperatures.
In the century which followed, this simple but effective treatmentcontinued even though it had unpleasant side effects. Salicylic acid isa strong irritant, causing bleeding and ulcers in the mouth andstomach. It was not until two chemists working for the German chemicalcompany Bayer made the derivative, acetylsalicylic acid, that thetreatment became relatively safe. That was in 1893, and the chemistswere Felix Hoffmann and Heinrich Dreser. Their product was namedaspirin, and for over a century it has brought relief to millions ofpeople around the world. Aspirin works by blocking an enzyme that makesprostaglandins, the chemicals which signal that the body has beeninjured or invaded by a micro-organism. Protaglandins are generated inexcess, and the result is inflammation, pain and fever.
Today in the USA around 20 billion aspirin tablets are taken eachyear, even though it is still a risky remedy and can cause stomachinflammation in some people. The best known form of aspirin is AlkaSeltzer, whose tablets also contains citric acid and sodium bicarbonate.The bicarbonate reacts with the aspirin to form its sodium salt, therebymaking it soluble in water and supposedly quicker acting, and reactswith the citric acid to generate bubbles of carbon dioxide. The citricacid also masks the taste of the aspirin.
Although aspirin has been used for a long time it is not without itsmore serious risks, and for some young children aspirin has proved fatal, whenthey have been given it to treat a viral infection like `flu or chickenpox. They developed what is known as Reye's syndrome, and althoughthis is extremely rare, it is best never to give aspirin to a childunder the age of 12.
Despite its disadvantages, aspirin is much more than just apainkiller, and is prescribed by doctors to patients who have suffereda heart attack because it inhibits the formation of those chemicalswhich cause blood platelets to aggregate together, which is what startsa blood clot. Aspirin is normally sold as 300 mg tablets, and these cansafely be taken at a rate of two every four hours to a maximum dose ofa dozen tablets (4 g) per day. A single dose of 10 g (30 tablets) cankill an adult because it makes their blood too acidic. The body triesto cope by rapid breathing to dispel [CO.sub.2] and thereby reduceacidity, and by boosting the action of the kidneys, which leads todehydration. If the acidity cannot be corrected by natural means,tissue damage occurs and eventually death.
More than half the people in developed societies die of heartdisease. Rather than wait until their heart is showing signs ofweakness, when they would be prescribed aspirin by their doctor, manynow believe they can escape this fate by the simple expediency oftaking a junior aspirin tablet every morning as a preventative. Such atablet contains a quarter of the normal dose, in other words 75 mg ofacetyl salicylic acid. What they may not realize is that they are alsogetting salicylate from other sources, notably their diet.
Some who fear for the health of their heart have been persuaded thatthey can fend off the grim reaper by eating the right type of fat. Theyavoid all animal fats and hydrogenated vegetable oils, and go for thosevegetable oils which are mainly mono-unsaturated. They may also haveread that those who drink red wine are also less prone to heart disease.All this advice for a healthy life appears to be sound, and those whoadvocate it can point to the people of the Mediterranean region whereheart disease is much less common than elsewhere. Clearly the diet ofthat region must hold the key, they say, and the focus tends to fall onolive oil and red wine. A chemical explanation is usually offered interms of mono-unsaturated fits, the main component of olive oil, andpolyphenol antioxidants, which are particularly abundant in the skinsof black grapes and which are extracted into red wine.
It may well be that the Mediterranean-style diet has another factor:salicylate. This is also present in many vegetables, herbs and fruits.Gazpacho, the soup made from tomatoes, onions and tarragon, andserved cold, may contain a healthy dose of salicylate, while ratatouille,the vegetable dish of aubergine, courgettes, red peppers and tomatoes, couldbe brimming with the stuff. Other foods from warm climes are relativelyrich in salicylate, such as pineapples, melons and mangoes, while currypowder has over 200 mg pre 100 g.
It is possible to plan a diet that will garner salicylate in gentlestages throughout the day. For example, if you like fruit at breakfastgo for raspberries: a bowl of them will provide 4 mg of salicylate. Ifyou want a salad at lunch then choose chicory leaves and add a coupleof gherkins: both have lots of salicylate. A liberal sprinkling oftomato ketchup on your hamburger and fries is also a good idea, and ifyou need a snack during the day then nibble a handful of currents orraisins.
The easiest way by far to boost your salicylate intake is to drinktea. A cup, made with one tea bag, will provide 3 mg, and if you drinkthe average 5 cups a day you will be getting a life-enhancing 15 mg.Coffee drinkers, on the other hand, would need to take in 20 mugs oftheir brew to get this amount. Other foods to boost your daily dose ofsalicylate are almonds, peanuts, coconut, honey, Worcester sauce,licorice, peppermint, broccoli, cucumbers, olives and sweetcorn. Andonly eat potatoes with their skins on: peel them and all the salicylateis gone. The same is true of pears. If you are going to a party you canenjoy salicylate in fruit juices, wines and beer.
Of course you may be one of the unlucky few per cent who react badlyto salicylate, and are advised to avoid aspirin because it can causestomach bleeding and ulcers. In which case you are probably likely toget indigestion from a diet rich in salicylate, so the best advice isto avoid foods like these. If you are hypersensitive to salicylate thenyou may even be put on a salicylate-free diet, but you need not feeldeprived because there are lots of zero-salicylate foods to choosefrom: meat, fish, milk, cheese, eggs, wheat, oats, rice, cabbage,brussels sprouts, celery, leeks, lettuce, peas and bananas have none atall. And if you fancy a drink then stick to spirits, but be careful tochoose the right mixer. Gin and tonic is fine, and so is rum and coke,but avoid Bloody Marys (vodka and tomato juice).
[] Portrait 9
Those unspeakable molecules--phthalates
Finally in this gallery we come to a portrait of a molecule that is presentin everything we eat: phthalate. There have been several scares aboutphthalates over the years: a recent one in the UK concerned theirpresence in formula feeds for babies. Mothers were alarmed to be toldthat phthalates were contaminating their baby's feed, and that thesemolecules were being described, somewhat mischievously, as `gender-bending'chemicals. The panic that resulted echoed an earlier phthalatescare of the 1970s when they were said to leach from plastic wrappinginto food, and were then accused of causing cancer. Despite theseworrying assertions, there is no need for alarm, because phthalatescause neither cancer nor infertility in humans, as we will discover.Phthalates are derivatives of phthalic acid, which consists of abenzene ring with two acid groups attached. These groups may be next toeach other, when the molecule is called simply phthalate, or onopposite sides of the ring, when it is called terephthalate. (There isa third form in which the groups are one atom apart, but these havelittle commercial significance.) Phthalates were first made in the1850s and called naphthalates, from naphtha, the ancient Greek name fornatural petroleum, but this was soon shortened to phthalate.
Phthalates are entirely manufactured and worryingly widespread;even in remote regions of the planet analysts have recorded 0.5 ppm ofphthalates in rainwater, so even the peoples of the high Himalayas andthe remote Pacific islands get a daily dose. The alarm over baby foodscame from a report by the UK's Ministry of Agriculture, Fisheriesand Food, which released surveys entitled Phthalates in Paper & BoardPackaging (1995) and Total Diet Survey (1996) which reported themto be present in almost all food analysed, not just in baby milk. Levels inmilk and milk products were reported to be around 1 ppm, and for a timeit looked as though this might be coming from the PVC tubing used inmilking machines, but investigation showed that this source accountedfor only a tenth of what was present.
Both kinds of phthalate are produced industrially. Terephthalate isused to make polyester for bottles and fibres; it is permanently fixedas an integral part of the polymer and poses no threat. We will beinspecting its portrait in Gallery 5. The other kind of phthalate goesinto plastics like PVC to make them pliable. PVC is a tough, rigidsolid used for window frames and drainpipes, but when phthalate isadded to it the plastic becomes flexible because this allows thepolymer chains to move over one another. In this way we get PVC thatcan be used as garden hoses, wallpapers, shower curtains, clothes,blood bags and water beds. However, it is electric cable and vinylflooring which uses most of the phthalate. This phthalate is not fixed,and is simply blended in to act as a molecular lubricant. If one ofthese phthalate molecules finds itself near the surface of the PVC itis free to escape--to be rubbed off or to evaporate into the air.
Because of earlier fears about their safety, plasticizer phthalatesare now among the most investigated of all chemicals. The leadingplasticizer is DEHP, short for di(ethylhexyl) phthalate, but accordingto David Cadogan, of the European Union's Council for Plasticizers andIntermediates in Brussels, this poses little risk: `As far as humans areconcerned it causes neither cancer nor reproductive effects. Nor arephthalates accumulating in the environment because they arebiodegradable, and levels are falling. In Rhine sediment, for example,there has been a reduction of 85% since the 1970s. Phthalates are veryinsoluble in water--about a millionth of a gram per litre--so leakagefrom plastics in old landfill sites is tiny.'
In 1990 the EU Commission said that DEHP should not be classifiedas a carcinogen, because no carcinogenic or oestrogenic activity wasfound with fish, hamsters, guinea-pigs, dogs or monkeys. However, ratsdid show increased risks of liver tumours and smaller testes, but theseanimals, unlike humans, are known to be particularly prone to respondthis way because they have been specially bred to be sensitive tocancer-forming chemicals. Humans are not at risk. The Danish Institute ofToxicology concluded that an intake of 500 mg a day was without effect.Our average daily intake is around 0.35 mg, which over a lifetime wouldamount to less than 10 g (a dessert spoonful). For babies, the tolerabledaily intake is 0.05 mg per kilogram of body weight, but no formula feedwould provide anything like this amount of DEHP. In any case the 0.05guideline has a large inbuilt factor and is based on the tests on rats.The danger from phthalates is negligible, even to babies. If all thephthalates in a year's supply of milk were to be consumed at onefeeding, it would still not be enough to make a baby sick, let aloneanything more serious.
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Excerpted from Molecules at an Exhibitionby John Emsley Copyright © 1999 by John Emsley. Excerpted by permission.
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