Subscribe to the OSS Weekly Newsletter!

A Taste of the Science of Aspartame

The artificial sweetener aspartame has garnered attention on two fronts. It has afforded a way to add sweetness to our lives without adding calories but has also spawned bitter discussions of its safety.

I first became interested in aspartame when I learned about the curious way in which its sweetness was discovered. Back in 1965, G.D. Searle Company chemist Jim Schlatter was carrying out research on gastric ulcers and certainly did not have artificial sweeteners in mind. He knew that entry of food into the stomach stimulated the secretion of gastrin, a hormone that triggers the production of gastric acid. At the time, the common belief was that ulcers were caused by excess stomach acid, and Schlatter was interested in finding a drug that could inactivate gastrin.  

In the course of this research, Schlatter synthesized some model compounds that incorporated certain features of the hormone. One day, after licking his finger to pick up a sheet of paper, he noticed a sweet taste, which he eventually traced to the “aspartylphenylalanine methyl ester” he had just synthesized. Little did Schlatter dream that within twenty years his discovery would be netting the company a billion dollars of profit a year! And he most certainly never imagined that his sweet crystals would become embroiled in a bitter scientific controversy.  

I got my first taste of that controversy around 1995 when I began to be asked about a circulating email claiming that aspartame was responsible for a cavalcade of health problems ranging from multiple sclerosis and depression to blindness and cancer. That email turned out to be the handiwork of one Betty Martini, founder of “Mission Possible World Health International,” an organization “committed to removing the deadly chemical aspartame from our food.” How this bee first got into her bonnet isn’t clear, but “Dr.” Martini, whose degree is an honorary Doctor of Humanities from an unaccredited Bible school, has kept up the crusade against aspartame to this day. Not surprisingly, she has also hopped onto the rickety anti-vaccine, anti-fluoride and anti-MSG bandwagons that rattle along with their load of poppycock. 

Is aspartame really a chemical from hell? No. But neither is it a heaven-sent weapon in the battle against obesity. The literature on the substance is voluminous and has been extensively reviewed by regulatory agencies around the globe with the conclusion that an acceptable daily intake (ADI) is in the range of 40-50 mg per kg of body weight. A person would have to consume more than twenty cans of diet soda to exceed this limit. Researchers at the Ramazzini Institute in Italy have misgivings about the ADI and point to their study in mice and rats that found an increased risk of cancer at exposures that approach the ADI. They also claim to have shown that prenatal exposures cause an increase in malignancies in rodent offspring at doses lower than the ADI. Actually, Health Canada, the U.S. FDA, and the European Food Safety Association have scrutinized the animal data and have concluded that they are not pertinent to human exposure.  

There is also the question of scientific plausibility. Aspartame breaks down in the body to release phenylalanine, aspartic acid and methanol, all of which are commonly found in a variety of foods in larger doses than those available from aspartame. The only concern is for people who suffer from a rare genetic condition known as “phenylketonuria” (PKU) who have to scrupulously avoid aspartame. While there have been rumblings in the anti-aspartame community that metabolism of the sweetener can yield diketopiperazine, a purported carcinogen, this has not been borne out by proper studies. 

In my view, the carcinogenicity argument can be dismissed. However, the claim that artificial sweeteners are of value in curbing the obesity epidemic has to be critically examined. On the surface, this makes sense because replacing a serving of sugar-sweetened soft drink with a diet drink saves about 150 calories. Nevertheless, a number of studies have shown that using artificial sweeteners does not lead to weight loss. It seems that people who use a sweetener in their coffee tend to reward themselves by having the slice of cake they would otherwise have shunned. Another possibility is that the use of these intense sweeteners overstimulates sweetness receptors on taste buds so that less intensely sweet foods such as fruits and vegetables are less satisfying and the craving for sweets increases.  

There is also a theory that the pleasure of sweetness stimulates the appetite which is then satisfied when the body receives calories. Taking that first bite of a sugar-sweetened cake encourages the consumption of the rest of the slice, but the craving stops when it has been consumed. However, an artificial sweetener stimulates the appetite without delivering satisfying calories. Those cookies in the jar may look pretty attractive after gulping a diet drink. A further concern is a study that linked long-term consumption of artificial sweeteners with a disruption of the balance of bacteria in the gut that in turn may be linked with glucose intolerance, a risk factor for type 2 diabetes. 

What then is my conclusion after stomping through the aspartame quagmire for a few decades? I have no concerns about safety. I have no reservations about using aspartame in my instant coffee. (I don’t use any sweetener in a real cup of coffee since it doesn’t need any.) But I do think that consumers are being seduced by advertisers, without sufficient supporting evidence, into believing that artificial sweeteners have an important role to play in weight control.  

Finally, let me address a question I have repeatedly been asked. What about diet sodas? I say avoid them, along with the sugar-sweetened ones. A study of 450,000 people in 10 European countries found that drinking two or more sweet-tasting beverages a day, whether sweetened with sugar or artificial sweeteners, is linked with early death and heart disease even in people with a healthy weight. Of course, such an association cannot prove cause and effect. After all, it may be that people who drink soft drinks are more likely to exercise less and have poorer diets. Still, given that such beverages have no nutritional value, why not just switch to good old H2O?


Leave a comment!

Back to top