When the first artificial sweetener (now sold as Sweet’n Low) was discovered in 1878, the world became divided between those who embrace artificial sweeteners to reduce calorie intake and sugar intake and those who fear that these sweeteners cause health problems. There are few places we hear this debate more than on the topic of Diet Coke, which contains the low-calorie sweetener aspartame instead of sugar or high fructose corn syrup. Diet versions of Pepsi, Dr. Pepper, Mountain Dew, and Sprite also contain aspartame. Many foods are sweetened with aspartame too, including some yogurts, gum, and nutrition bars.
Aspartame has safety approval from the Food and Drug Administration (FDA) and Europe’s Scientific Committee on Food.1Public Health Service Food and Drug Administration. Department of Public Health and Human Services. Fed Regist 46, 38284-38308 (1981). https://www.fda.gov/downloads/Food/IngredientsPackagingLabeling/FoodAdditivesIngredients/UCM404380.pdf2Commission of the European Communities. Reports for the Scientific Committee for Food. food – science and techniques 16, (1985). http://aei.pitt.edu/40825/1/16th_food.pdf Aspartame’s safety was reaffirmed in 2013 by the European Food Safety Authority.3Opinion on the re-evaluation of aspartame (E951) as a food additive. https://www.efsa.europa.eu/en/efsajournal/pub/3496 Additionally, aspartame has been deemed safe for human consumption by regulatory agencies in over 100 different countries.4Butchko, H. H. et al. Aspartame: review of safety. Regul. Toxicol. Pharmacol. 35, S1-93 (2002). https://www.sciencedirect.com/science/article/pii/S0273230002915424?via%3Dihub
I know aspartame has been approved, but how safe is it, really? I’ve read that it can cause brain cancer, neurological issues, and can mess up my metabolism.
Aspartame is mainly two amino acids, building blocks of proteins, joined together. When you consume it, aspartame travels to your small intestines where it is completely broken down to release these two amino acids, phenylalanine and aspartic acid, plus methanol.3Opinion on the re-evaluation of aspartame (E951) as a food additive. https://www.efsa.europa.eu/en/efsajournal/pub/3496 These three products then enter your bloodstream. The amino acids are used to make proteins and neurotransmitters, or break down and leave your body. Methanol is broken down within minutes, leaving your body in urine or in your breath.3Opinion on the re-evaluation of aspartame (E951) as a food additive. https://www.efsa.europa.eu/en/efsajournal/pub/3496
Aspartame itself is not absorbed into the bloodstream, so the real question about safety centers around aspartame’s breakdown products: phenylalanine, aspartic acid, and methanol.5Magnuson, B. A. et al. Aspartame: a safety evaluation based on current use levels, regulations, and toxicology and epidemiological studies. Crit. Rev. Toxicol. 37, 629-727 (2007). https://www.tandfonline.com/doi/full/10.1080/10408440701516184
It may surprise you that these products are found in foods you eat every day! Phenylalanine and aspartic acid are abundant in meats, legumes, dairy products, and nuts. Methanol is present in fruit and vegetable juice. In fact, you get more amino acids and methanol from these foods than from Diet Coke, since aspartame is present in small concentrations. Tomato juice contains six times more methanol than diet soda, and milk contains six times more phenylalanine and thirteen times more aspartic acid than the same volume of diet soda.5Magnuson, B. A. et al. Aspartame: a safety evaluation based on current use levels, regulations, and toxicology and epidemiological studies. Crit. Rev. Toxicol. 37, 629-727 (2007). https://www.tandfonline.com/doi/full/10.1080/10408440701516184
Regardless, concerns about safety remain and research has addressed many of them.
• Brain cancer and neurological issues: In the early 1970s when the FDA considered approving aspartame as a sweetener, a doctor and a consumer group brought forward concerns that the amino acids released from aspartame could become neurotransmitters that are toxic to the brain, especially in children. They also voiced concerns that aspartame might cause brain cancer. The FDA took these claims very seriously, and stayed their approval of aspartame for two years while they and a neutral outside organization audited fifteen key studies that supported aspartame safety. The FDA then created a safety board, which heard testimony from both sides for three full days. The board called for more research, which culminated in aspartame’s approval by the FDA.1Public Health Service Food and Drug Administration. Department of Public Health and Human Services. Fed Regist 46, 38284-38308 (1981). https://www.fda.gov/downloads/Food/IngredientsPackagingLabeling/FoodAdditivesIngredients/UCM404380.pdf Many more research studies have since confirmed that people cannot physically drink enough diet soda to damage their brain, develop behavioral issues, or develop cancer, even with long-term consumption.5Magnuson, B. A. et al. Aspartame: a safety evaluation based on current use levels, regulations, and toxicology and epidemiological studies. Crit. Rev. Toxicol. 37, 629-727 (2007). https://www.tandfonline.com/doi/full/10.1080/10408440701516184
• Metabolism issues: There are recent concerns that aspartame may alter what bacteria populations live in your intestines, which could affect many aspects of overall health.6Korem S. J. et al. Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature. 514, 181-186 (2014). https://www.nature.com/articles/nature13793 However, there isn’t much evidence to support this and research is still ongoing.7Spencer M. et al. Artificial sweeteners: A systematic review and primer for gastroenterologists. J Neurogastroenterol Motil. 22, 168-180 (2016). http://www.jnmjournal.org/journal/view.html?doi=10.5056/jnm15206
If aspartame has been proven safe, why is there still a controversy about it?
Controversy exists because research studies questioning aspartame safety have and continue to be published. How can aspartame be considered safe if this is the case, you ask? There are two main things to keep in mind when reading any study on aspartame:
- A study is only as good as its design. Unfortunately, many of these studies involve feeding animals more aspartame than a human could ever consume… like the equivalent of 1,400 cans of diet soda. This is a problem on its own, but can also cause the animal to eat less food and develop nutritional deficiencies, which can result in health problems that are then attributed to aspartame. This is one criticism of studies showing gut microbiome changes after aspartame consumption.
- Association and observational studies can be useful, but can’t show causation. For example, a recent study found that postmenopausal women who drink 2 or more diet sodas per day have a higher risk of stroke than other postmenopausal women, which suggests that diet soda increases risk of stroke. However, these women were also the most likely to be obese, which could also account for their increased stroke risk.8Mossavar-Rahmani Y. et al. Artificially Sweetened Beverages and Stroke, Coronary Heart Disease, and All-Cause Mortality in the Women’s Health Initiative. Stroke. 50, 555-562 (2019). https://www.ahajournals.org/doi/10.1161/STROKEAHA.118.023100
Are there people who should avoid aspartame?
Individuals with certain genetic conditions, such as phenylketonuria (PKU), may need to limit aspartame in their diet since they can’t process phenylalanine very efficiently.9Mayo Clinic https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/phenylalanine/faq-20058361
How much Diet Coke can I safely drink?
The FDA set the acceptable daily intake of aspartame at 50mg per kg of body weight per day and the European recommendation is slightly lower at 40mg of aspartame per kg of body weight per day.5Magnuson, B. A. et al. Aspartame: a safety evaluation based on current use levels, regulations, and toxicology and epidemiological studies. Crit. Rev. Toxicol. 37, 629-727 (2007). https://www.tandfonline.com/doi/full/10.1080/10408440701516184 A 12oz can of Diet Coke contains ~187mg of aspartame. For example, a 100 pound person could drink 12 cans of Diet Coke in a day before reaching the American-set aspartame limit.
Even though aspartame is safe, keep in mind that there are good reasons you shouldn’t drink Diet Coke all day, every day. For one, it provides essentially no nutrition while the acid can harm your teeth!
That said, the major body of scientific data shows that it is safe to enjoy aspartame-sweetened foods and drinks in reasonable amounts.