Drink Your Diet Soda with Abandon

Doniel Weinreich

In a January article, Michelle Shakib drew a number of negative conclusions on the effects of aspartame. I would like to defend aspartame from these erroneous attacks. While for the purposes of this article I will focus primarily on aspartame, many of my claims can be applied to other non-nutritive sweeteners as well.

Any discussion of aspartame should start with the fact that it is recognized as safe for consumption by the U.S. Food and Drug Administration (FDA), the European Food Safety Authority (EFSA), Health Canada, the American Medical Association, the American Cancer Society, the American Diabetes Association, the American Heart Association, as well as a myriad of other government agencies and independent scientific organizations. In fact, I’m not sure there is a single such group opposed to the use of aspartame. This would be highly unlikely if, as Ms. Shakib suggests, there was good evidence that consumption of aspartame leads to cancer and mental retardation. But there is in fact no such evidence.

Ms. Shakib’s first claim was that aspartame is metabolized into a number of “toxins,” primarily methanol, phenylalanine, and aspartic acid—all very scary sounding words. But aspartic acid and phenylalanine—while, like anything, can be toxic in very large amounts—are not toxins; they are amino acids—the building-blocks of proteins—and are essential for human life. Aspartic acid is being synthesized by your body right now and is abundant in nearly all animal products and many legumes, and phenylalanine is similarly present in protein-rich foods. Furthermore, the dose makes the poison. A single chicken breast contains over 2600 mg of aspartic acid and over 1100 mg of phenylalanine, a cup of boiled spinach contains 450 mg and 241 mg respectively, while a can of diet soda breaks down into approximately 72 mg and 90 mg. Yet no one suggests that chicken or spinach lead to neurological damage. The effects of phenylalanine that Shakib described only apply to people with phenylketonuria, a rare genetic disorder that affects less than 0.01% of the population.

The only byproduct of aspartame that is actually a toxin is methanol, which does break down into formaldehyde and eventually formic acid, which can be toxic. However, once again, the dose makes the poison; higher amounts of methanol are found in citrus fruits and tomatoes. Studies have even been done measuring blood concentration of methanol, formaldehyde, and formic acid in humans after consumption of aspartame at various doses; no elevated levels of methanol were detected after normal intake, and no elevated concentrations of formaldehyde or formic acid—the primary cause of methanol poisoning—were detected even after doses of  aspartame 4 times the FDA recommended daily maximum (approximately 80 cans of diet soda).

Shakib’s other argument was the much more popular myth that diet soda causes cancer, despite the FDA, NCI, and ACS claiming otherwise. The evidence for this claim almost always inevitably involves mice and rat studies. The specific study cited by Ms. Shakib, like many of the studies linking non-nutritive sweeteners to cancer in mice, was done by the European Ramazzini Foundation (ERF). The ERF has been much derided in the past by the scientific community and numerous regulatory agencies for the severe methodological flaws and lack of detail in their studies as well as the irreproducibility of their findings. This specific study was in fact reviewed by the EFSA in 2011 and they concluded that the design was flawed, noting the inordinate length of the study, the high predisposition of the mice used to incidental cancers, the instances of cancer in the study actually falling within the normal range, and the irrelevance to humans.

One must always be careful drawing conclusions from rat studies; their results are often inapplicable to humans. After the first ERF study in 2005 claiming to link aspartame to leukemia and lymphoma, the National Cancer Institute analyzed data on over 500,000 people and found no association between aspartame consumption and leukemia, lymphoma, or brain cancer.

When advising against something, it is always important to consider the pragmatic alternatives. If one were to forgo artificially-sweetened beverages in favor of unsweetened ones, there would obviously be no harm done (other than depriving your taste buds). However, according to my nonscientific observations, this is not what is generally done. Due to the chemophobic demonization of non-nutritive sweeteners, it seems people are more likely to avoid artificially-sweetened beverages in favor of their sugar-sweetened counterparts. And while non-nutritive sweeteners are unequivocally safe for consumption, sugar—which Americans already consume far too much of—is known to cause obesity, diabetes, cardiovascular disease, tooth decay, and possibly several other health problems. Sugar should be the enemy, not aspartame.