Artificial sweeteners taste sweet for dogs
200,000 times sweeter than sugar
Artificial sweeteners have hardly any calories, do not strain the metabolism, and do not damage teeth. Does the coin have no downside?
(Chart on artificial sweeteners: PDF)
The chemist Constantin Fahlberg evidently did not wash his hands before going to table - a negligence with unexpected consequences. In 1878 Fahlberg, who came from Russia and did his doctorate in Leipzig, experimented with the oxidation of hydrocarbons from tar for his habilitation in Baltimore, USA. An experimental approach boiled over, and the scientist accidentally spilled some of the liquid onto his hand. Later, when he put bread in his mouth while eating, he noticed a sweet taste.
By chance, Fahlberg discovered the world's first artificial sweetener: benzoic acid sulfimide. The substance is around 500 times sweeter than ordinary sugar, which chemists call sucrose in the jargon. Fahlberg named the artificial compound saccharin, patented the manufacturing process and founded a factory in Magdeburg with his uncle. Business flourished. Real sugar - whether made from cane or turnip - was still a luxury at the end of the 19th century (see article “The Queen's Black Teeth”). As the “poor people's sugar”, the cheaply produced industrial good soon reached a volume of 175 tons per year. This corresponds to the sweetness of almost 90,000 tons of sugar - around an eighth of the amount of sugar that was consumed in the German Reich at that time.
Today, artificial sweeteners in colorful bags or practical plastic dispensers are used in millions of households and in every restaurant. As an additive, they can be found in all kinds of foods across the supermarket, in light lemonades, but also in diet desserts, sweets, yogurts and salad dressings. They are contained in chewing gum that is gentle on teeth, because the bacteria that cause tooth decay can only do something with real sugar; substitutes are spurned. The industry even mixes sweeteners in toothpaste to mask unpleasant taste notes, as well as in cosmetics and medicines.
Artificial sweeteners offer one of several ways to replace sugar. They are often mistaken for the sugar substitutes. To differentiate: Artificial sweeteners taste at least ten times sweeter than sugar and are practically calorie-free. Sugar substitutes, on the other hand, taste about as sweet as sugar and contain half as many calories as sugar. The main difference between them and sugar is that the human body processes them by bypassing the hormone insulin, which regulates blood sugar (see article «Must sweets be a sin?»). That is why they are suitable for diabetics. And they are tooth friendly. Some of them are even able to prevent tooth decay from occurring. Like sugar, sugar substitutes are carbohydrates (their molecules are made up of carbon, hydrogen and oxygen atoms). Fruit sugar (fructose) is, for example, a sugar substitute as well as the sugar alcohols sorbitol, xylitol, mannitol, maltitol, lactitol and isomalt.
The actual sweeteners, on the other hand, are absorbed by the human body, but most of them are excreted unchanged. In addition to saccharin, there are currently seven other substances in Switzerland and the European Union
Approved for human consumption: acesulfame-K, aspartame (brand name Assugrin), cyclamate, neohesperidin, thaumatin, and since the beginning of this year also sucralose (brand name Splenda, see article “Bitter battle for sweet margins”) and aspartame-acesulfame salt.
Science knows dozens of other synthetic or plant-derived sweeteners with names such as Brazzein or Miraculin and with strange properties. Some are poisonous, some are not heat-resistant or insoluble in water, with some the sweetness impression is delayed or lasts an unusually long time. What they have in common is that they exceed the sweetness of normal sugar many times over. With a factor of 30, cyclamate is one of the weakest. The most potent, like lugdunam or sucrononate, are an unimaginable 200,000 times sweeter than table sugar.
Sweetness cannot be measured objectively with instruments. Only experienced sensory experts can do this with the help of the most archaic of all senses, taste perception. To do this, the professional gourmets compare a defined amount of sugar in aqueous solution with differently concentrated solutions of the sweetener to be examined until the sweetener concentration is found that gives the testing tongue the same impression of sweetness as the sugar water.
Why does something taste sweet at all? It was only four years ago that an American neurobiologist with the aptly named Charles Zuker succeeded in unraveling the secret of the human perception of sweetness: With just one type of taste receptor, we can perceive all possible molecules as sweet. Receptors are proteins that are found in large numbers in the sheaths of the sensory cells on the tongue. Individual sections of the protein framework are designed as docking points. These “recognize” certain molecules that swim past the tongue and connect with them. Click - and the cell sends a signal to the brain: sweet! The sweet receptor has a whole range of differently shaped docking points. The household sugar sucrose fits into one of them, while another absorbs the sweetener dulcin. Depending on the docking point, the perception of sweetness is apparently weaker or stronger. Different docking sites also behave differently: the one for saccharin, for example, becomes stubborn when there is overstimulation. From a certain saccharin concentration onwards, it blocks the signal transmission to the brain, which is why saccharin tastes less sweet in high concentrations than in low ones.
The shape of the sweetener molecules also causes some of them to have a bitter note. At the same time as the sweet receptor, they also set in motion those receptors that report bitterness to the brain, as researchers at the German Institute for Nutritional Research in Potsdam recently showed: two of the thirty types of bitter receptors that humans have recognize saccharin and acesulfame-K .
The artificial sweeteners are completely astonishing when you mix them: The combined sweetness is then far above that of the sum of the individual components. Acesulfame-K and aspartame, for example, mixed in a ratio of one to one, are increased by up to 100 percent. This means that you only need half the amount of sweetener to replace the same amount of sugar. On top of that, one component of the mixture can hide the disadvantages of the other. Cyclamate largely suppresses the bitter taste of saccharin.
The producers have to mix for another reason: although sweeteners are sweeter than sugar, they lack bulk, “body”, as food technologists say. Artificially sweetened foods as well as sweeteners for household use are therefore brought to volume with filling materials. Sugar substitutes or starch breakdown products are usually used for this purpose. These add a few calories to the product, but the high sweetness of the mixture partially compensates for this. Sucralose, for example, 600 times sweeter than sugar, is unsuitable for household use in its pure form. In North America, it's made with glucose or maltodextrin and can be used like sugar for cooking and baking, with a tenth of the calories. Even light drinks contain such filling sweetness, because otherwise they lack the "mouthfeel", the correct sensory impression of the drink in the oral cavity. This is one of the main disadvantages of artificial sweeteners: in terms of texture, taste and processing options, they cannot match sugar.
What distinguishes sweeteners most clearly from household sugar is the structure of their molecules. They are a wildly thrown together heap made up of members of 18 different chemical substance classes. Only a few distant relatives of household sugar are among them.
This is explained by their history: most of the sweeteners were found by pure chance. Its discoverers had very different ideas in mind. Aspartame, for example, was a waste product of the search for a drug for stomach ulcers. Cyclamate owes its career as a sweetener to a doctoral student who put the cigarette on the laboratory table in 1937 while trying to synthesize antipyretic drugs. When he put it back in his mouth, it tasted sweet. A German chemist found acesulfame-K in a similar way in 1967: he licked his finger to flip through a pile of paper. The research department of the British sugar company Tate & Lyle also stumbled upon sucralose by chance: In the 1970s, chemical compounds were examined to see whether they could be used as starting materials for chemical syntheses. A foreign doctoral student was commissioned to test chlorinated sugar molecules. Instead of “test”, however, the good man understood “taste” - and tasted sensational sweetness.
The chemical diversity - not the fact that they are artificially produced - makes the calorie-free ones suspicious: do you really know what they are doing in the body while they seemingly rush through untouched?
Warnings can be found everywhere you look. Aspartame has recently come under fire for causing leukemia and lymph cancer in rats, according to a new Italian study. Sucralose - approved in Canada since 1991 and in the USA since 1998 - has also come under fire: As can be seen from the approval documents, up to a third of the amount ingested enters the metabolism. Opponents of sucralose suspect that the chlorinated sugar is broken down into toxic compounds there and that it may cause cancer in the long term. All studies that certified the product harmless were paid for by the manufacturer.
That alone does not have to mean anything: As in the pharmaceutical industry, it is also common in the food sector for those who want to sell it to test a product. What is certain is that the responsible bodies of the World Health Organization, the EU and the USA carefully examine all available data before they let loose a new sweetener on humanity. It takes an average of twenty years from discovery to approval. Feeding experiments on rats, toxicological tests and the investigation of possible genetic changes are standard. On the basis of the results, the experts determine how much of a substance remains without undesirable side effects. To be on the safe side, divide the value by a hundred again, the result is the recommended maximum daily consumption. If new studies come to different results, these will also be scrutinized carefully and the procedure may be rolled out again. This could also happen in the case of the Italian aspartame study.
However, it is noticeable that the health authorities in different countries classify other substances as safe for their populations. Stevia, a natural extract from the leaves of the South American sweet herb, has been allowed in Japan for decades, but banned in Switzerland and the European Union. Reason: A risk to consumers cannot be completely ruled out. Feeding experiments on rats had shown that components of the extract are mutagenic and can impair fertility in male animals. Cyclamate, on the other hand, is approved in Europe, while it is under a ban in the USA. The reason: Bacteria live in the intestines of a few people, some of which convert the sweetener into a weakly toxic breakdown product.
In the late 1960s, saccharine and cyclamate were suspected of causing bladder cancer. This followed from studies with rats, whereupon the US and some other countries withdrew the sweetener from the market. However, the test animals were fed very large amounts of the two substances, and the results could not be reproduced later, so the ban was lifted again.
What Paracelsus already knew also applies to sweeteners: the dose alone determines whether a thing is poison. After all, real sugar, if consumed in excess, leads to all kinds of diseases.
One more question remains: does calorie-free sweetness really make the pounds disappear? There have also been doubts there since the 1980s, which have been nurtured by scientific studies. According to one of these studies, test animals fed saccharin were generally hungrier and ate more than control animals fed sugar. And a study of 80,000 women found that those of them who used sweetener did not lose weight, but gained weight - more than those who did without it. The explanation for this was as follows: The sweet signal triggers the reflex “spill out insulin” in the brain, as does real sugar. The hormone then rushes onto the blood sugar that is still in the bloodstream and sends it to further processing. However, a low blood sugar level triggers the alarm message to the brain: Hunger!
As evidence for this theory is repeatedly cited: Saccharin is used in pig fattening as an appetizer. There are of course more recent studies that do not prove the appetite-promoting effect. In addition, the biochemical proof of the reflex allegedly triggered by sweeteners has so far failed to materialize.
Who is right? Until that is clearly clarified, all that remains is: wait and see and drink unsweetened tea.
Sabine Sütterlin is a freelance journalist; she lives near Hamburg.
This article comes from the March 2006 NZZ Folio magazine on the subject of "Sugar". You can order this issue or subscribe to the NZZ Folio.
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