Science Explained: Aspartame

Parsing the evidence against aspartame

Aspartame, the low-calorie sweetener known on food labels as E951, was first approved for Canadian consumption in 1981. Aspartame is found in many products, including diet beverages, processed foods, yogurt and chewing gum. It’s also the main ingredient of the coffee and tea sweeteners Nutrasweet and Equal.

In the late-‘90s there was an uproar over whether aspartame was safe for consumption, and it has since become the most heavily tested food additive of all time. Just last month Diet Pepsi was reformulated in the United States, replacing aspartame with sucralose, also known as Splenda. Canada’s Diet Pepsi, however, did not get the same alteration.

This may lead us to wonder whether Pepsi is just trying to please their customers, or if they know something that we don’t.

The late-‘90s saw a conspiracy theory spread via chain letter emails warning that aspartame causes “multiple sclerosis, systemic lupus, methanol toxicity, blindness, spasms, shooting pains, seizures, headaches, depression, anxiety, memory loss, birth defects, and even death.” Health Canada has rejected these claims, and states that aspartame is safe for anyone who doesn’t have phenylketonuria, a condition that requires patients to follow a diet low in phenylalanine—one of aspartame’s main components. Aspartame is composed primarily of phenylalanine, and aspartic acid, both amino acids required for the body to function. The last 10 per cent is methanol, which metabolizes to formaldehyde—a known human carcinogen.

The research that has since come out indicates that aspartame can be anywhere from safe to harmful, making it challenging for consumers to understand whether it is a better alternative than the original sugary refreshment. A study published by the National Centre for Biotechnology Information (NCBI) states that individuals who have a history of mood disorders are at a higher risk of aspartame’s adverse effects, such as nausea, headaches, depression, nervousness, and forgetfulness.

In addition, a prospective cohort study from the American Journal of Clinical Nutrition (AJCN) followed 60,000 pregnant Danish women, and found that the consumption of aspartame-sweetened drinks increased the risk of preterm delivery. The sweetened version of the soda did not show the same results, leading researchers to believe it was caused by the aspartame. They concluded that the premature birth was most likely due to the extra methanol, from the diet soda, present in the uterus.

A controversial 22-year study was conducted at the Brigham and Women’s Hospital and Harvard Medical School to determine whether aspartame consumption increased the risk of certain blood cancers. The results found that only men who drank at least one diet soda a day had increased risk of NHL (non-Hodgkin lymphomas) and multiple myeloma, but also found increased risk in high sugar-sweetened soda consumption. Researchers could not explain the association in the two studies since there was no evidence that sucrose, fructose and sugar consumption increased the risk for these types of cancers. Only 38 per cent of the sample size in the study was composed of men, while the rest was made up of women. Since the sample size of men was relatively small, this could play a role in perceived risk difference between men and women. Despite the controversy of this study, it is important to note that this is the longest study ever conducted on human consumption of aspartame.

In December of 2013, the European Food Safety Authority issued a press release discussing their comprehensive risk assessment on aspartame, claiming it is safe at the Acceptable Daily Intake of 40mg/kg of body weight per day. This would be almost 15 diet sodas for a 150-pound individual. A panel of experts reviewed a large body of published and unpublished aspartame studies concluding it was safe; that it does not cause cancer or gene damage, does not impair cognitive function on the nervous system, and poses no risk to a developing fetus.

In 1965, James Schlatter, a chemist working at the time for the pharmaceutical company G.D. Searle & Company, discovered aspartame. Twenty years later Monsanto, a controversial agricultural biotechnology company, acquired the company and consequently, aspartame. Monsanto then created Searle Pharmaceuticals and the product Nutrasweet, and in 2000 went on to sell Nutrasweet.

It is often hard to interpret the large amounts of evidence in cases like aspartame, where science and politics converge. One party, in this case, Monsanto, is spending millions of dollars trying to protect the reputation of their product, and the other party is concerned for the public health and safety.

Despite what studies show, diet soda can lead to cognitive distortion, and can confuse the body’s response. When we consume calorie-free beverages, we go on to reward ourselves by spending the saved calories on something else—we indulge in two slices of cake at dessert, rather than just one. Calorie-free sweeteners are often much sweeter than sugar—aspartame and stevia are both 200 times sweeter than sugar in the same concentration. When we consume sweet foods, our brain is expecting calories to follow, and when they don’t our body gets confused and is driven towards consuming more sugar. For reasons such as these, all calorie-free sweeteners have controversies surrounding them.

None, however, have quite as much baggage as aspartame.