Pepsi has announced that it will remove aspartame from its formulation of diet Pepsi products in the US this year. Apparently this is a reaction to a 5% drop in the sales of Pepsi. Seth Kaufman, vice-president of Pepsi, said “Aspartame is the number one reason consumers are dropping diet soda.”

This move comes in the same week that Chipotle announced it is removing GMO food from its food chain. Unlike Pepsi, who cited only public opinion, Chipotle went one step further and directly cited pseudoscientific fears of GMOs as their justification. (But that’s another story.)

Like GMOs, aspartame has been widely studied and found to be safe, but remains the target of fear-mongering and conspiracy theories. It is not clear why this one food additive has continued to be the target of a fake controversy, other than that fears and conspiracies can take on a life of their own. The best example of anti-aspartame conspiracy theories comes from Janet Starr Hull, who wrote:

I will never accept the news of aspartame safety. I think it is a “business” decision to discredit/discount the research results that aspartame DOES cause cancer, major nerve disorders, birth defects, and brain imbalances. Think about it – can you imagine the chaos that will occur when the truth of aspartame dangers is accredited. The FDA has known about the dangers, the corporations have known about the dangers, and the medical community (if it is really worth anything) has known about the dangers.

That is a common claim of conspiracy theorists – the truth is being suppressed out of fears that it will bring chaos if revealed. I think our society will survive Pepsi moving over to a different sweetener.

There have been hundreds of studies showing aspartame is safe in the amounts consumed in food (unless you have a disease known as phenylketonuria). The first systematic review of this evidence was published in JAMA in 1985, and concluded:

Available evidence suggests that consumption of aspartame by normal humans is safe and is not associated with serious adverse health effects.

A 2002 review found:

The safety testing of aspartame has gone well beyond that required to evaluate the safety of a food additive. When all the research on aspartame, including evaluations in both the premarketing and postmarketing periods, is examined as a whole, it is clear that aspartame is safe, and there are no unresolved questions regarding its safety under conditions of intended use.

A more recent 2007 systematic review found:

The studies provide no evidence to support an association between aspartame and cancer in any tissue. The weight of existing evidence is that aspartame is safe at current levels of consumption as a nonnutritive sweetener.

They specifically found no association with any cancer. A 2012 updated review found:

In the Nurses’ Health study and the Health Professionals Followup study some excess risk of Hodgkin lymphoma and multiple myeloma was found in men but not in women; no association was found with leukemia. In the NIH-AARP Diet and Health Study, there was no association between aspartame and haematopoietic neoplasms. US case-control studies of brain and haematopoietic neoplasms also showed no association. The NIH-AARP Diet and Health Study and case-control studies from California showed no association with pancreatic cancer, and a case-control study from Denmark found no relation with breast cancer risk. Italian case-control studies conducted in 1991-2008 reported no consistent association for cancers of the upper aerodigestive tract, digestive tract, breast, endometrium, ovary, prostate, and kidney. Low calorie sweeteners were not consistently related to vascular events and preterm deliveries.

The slight increased risk for men in the Nurse’s Health study was not replicated in the other studies and likely just represents noise in the data. You always have to look at the totality of evidence and the statistical spread of results. There are always going to be outliers in any large data set.

Of course this provides the opportunity for those with a dedicated agenda or ideology to cherry pick the inevitable positive studies. In any case, the scientific data with regard to the safety of aspartame is very clear. It is one of the most studied food additives, with multiple independent studies and reviews, with a comfortable margin of safety.

Not only the FDA, but the European Food Safety Authority has reviewed the data and concluded that aspartame is safe.

Health Canada has a helpful page in which they review many of the internet fear-mongering memes relating to aspartame, linking the additive to many diseases, and showing that none of them are supported by evidence. The World Health Organization has assigned an acceptable daily intake level for aspartame of 40mg/kg/day. (The FDA uses 50mg/kg/day). Even if we take a 50kg person (that’s 110 pounds), 2,000 mg per day would be an acceptable intake of aspartame. The highest amount of aspartame found in an 8oz diet drink is 125 mg, which comes out to 16 cans, or almost 4 liters (over a gallon!), a day. This is well below actual consumption:

Consumption estimations for aspartame from one such method, the food intake survey, have been done in the United States, Canada, Germany, and Finland. APM consumption in all age groups and selected subpopulations, even at the 90th percentile, is approximately 2-10 mg/kg/day and is thus well below the ADI.


Aspartame is one of the most studied food additives in the world. It has been a common food additive for over 30 years, and there is a strong consensus among scientists and regulatory agencies that it is completely safe.

The fear and conspiracy genie, however, is difficult to put back into the bottle. In an ideal world corporations would stand strong in defense of science vs pseudoscience, but it is understandable that they would cave to popular opinion even when it conflicts with reality. They are in a no-win situation.

I would argue, however, that in the long run capitulating to public fear based on pseudoscience and rumor is a losing strategy. It just makes corporations more vulnerable to the Food Babes of the world, who can use the internet to push buttons of fear, disgust, and conspiracy to demonize any product.



Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.