Does Diet Pop Cause Cancer?

First of all, I’m from Pittsburgh and we call it POP, not soda.

Second of all, the above question is a bit too broad. The question we should be asking is, “Does the artificial sweetener, aspartame, cause cancer”? Found in Diet Coke, Diet Pepsi, and Diet Mountain Dew, aspartame is one of the most common artificial sweeteners used in today’s food industry.

diet coke

What Is Aspartame?

Aspartame is also commonly known as NutraSweet or Equal. It is comprised of a methyl ester of aspartic acid and phenylalanine dipeptide. The majority of use for aspartame is in low-calorie, low-carbohydrate, sugar-free beverages. Gram for gram, aspartame has the same caloric content as sucrose (4 calories/gram). However, because aspartame is nearly 200 times sweeter than sucrose (table sugar), much less is needed in order to obtain the desired sweetness in foods and drinks. So much less, in fact, that companies can claim “zero calories” on food labels.

Physiologically, aspartame is digested by becoming hydrolyzed in the intestinal lumen by esterases and peptidases into aspartic acid, methanol, and phenylalanine, where these individual components are then absorbed into the general circulation. Aspartame is a white powder that is stable under dry conditions, but degrades in high temperatures.

aspartame chemical structure

Artificial sweeteners, such as aspartame, are regulated by the U.S. Food and Drug Administration (FDA). The FDA approved the use of aspartame for use in dry foods in 1981 and for general purposes in 1996. The first use of aspartame in carbonated beverages was in 1983. Today, aspartame can be found in more than 6,000 foods and pharmaceuticals worldwide.

What Products Contain Aspartame?

You may be surprised at the extensive and varied list of products that contain aspartame.

  • NutraSweet
  • Equal
  • diet or sugar-free soft carbonated soft drinks
  • breath mints
  • cereals
  • chewing gum
  • flavored syrups for coffee
  • flavored water
  • frozen ice cream novelties
  • fruit spreads
  • sugar-free gelatin
  • hard candies
  • ice cream toppings
  • no-sugar-added or sugar-free ice cream
  • iced tea
  • instant cocoa mix
  • jams and jellies
  • juice drinks
  • maple syrups
  • meal replacements
  • mousse
  • nutritional bars and drinks
  • puddings
  • sugar-free cookies
  • sugar-free ketchup
  • vegetable drinks
  • yogurt (drinkable, fat-free, sugar-free)

How Much Is Too Much?

The FDA has set an “acceptable daily intake”, or ADI, for each artificial sweetener. The ADI is set as the maximum amount considered safe for consumption each day during a person’s lifetime.

The U.S. ADI for aspartame is 50 mg per kg of body weight (mg/kg). The European Food Safety Authority has recommended a slightly lower ADI at 40 mg/kg.

To put this into perspective…

The average 12 oz can of diet pop contains 180 mg of aspartame.

For an average individual weighing 68 kg (or 150 pounds), the ADI level would be 3409 mg of aspartame

That is nearly 19 cans of diet pop per day!

It is safe to say that even the most avid diet beverage drinkers consume well below their ADI for aspartame. To prove this, diet soft drink consumption has increased over the past 20 years from 4.8 oz per person per day in 1984 to 5.5 oz per person per day in 2004 (see graph below). Nevertheless, the 5.5 oz is WELL below the FDA approved ADI for aspartame consumption.

diet drinks graph

Does Aspartame Increase the Risk for Cancers?

This is a question that has been debated for over the past 20 years. The overall consensus from most national health agencies is that, NO, there is no conclusive evidence that aspartame consumption increases the risk for cancer.

In a 100-page scientific review paper, the safety of aspartame was evaluated on several parameters. In regards to cancer, “There is no evidence to support an association between aspartame and brain or hematopoietic tumor development”. This extensive journal article reviewed both animal and human studies and found that most of the animal studies used aspartame levels well above the ADI, often in doses up to 4,000 mg/kg of body weight.

In a study published in 2012 in the American Journal for Clinical Nutrition, researchers prospectively evaluated and assessed the diets of >125,000 individuals over a 22-year period (from the Nurses Health Study and Health Professionals Follow-Up Study). Results found that, in men, >1 serving of diet soda increased the risk of non-Hodgkin lymphomas (RR: 1.31, 95% CI) and multiple myeloma (RR: 2.02, 95% CI) compared to men who reported no diet soda consumption. There was no significant difference found in women subjects. Interestingly, however, researchers also found a significantly greater risk of men (not women) developing non-Hodgkin lymphoma in subjects who consumed regular sugar-sweetened sodas. In summary, because of the differential effects on men vs. women and because of the apparent cancer risk in individuals who consume regular soda, it is difficult to interpret these results and put the full blame on aspartame as the cancer culprit.

In conclusion, the following are statements made by several national health agencies and associations regarding the consumption of aspartame and cancer:

  • The American Cancer Society states, “There are no health problems that have been consistently linked to aspartame use”.
  • The National Cancer Institute states, “There is no clear evidence that the artificial sweeteners available commercially in the United States are associated with cancer risk in humans”.
  • In a position paper by The Academy of Nutrition and Dietetics, “Studies have found no evidence of a wide range of adverse effects of aspartame, including hypersensitivity reactions, elevated blood methanol or formate levels, and hematopoietic or brain cancers”.
  • The FDA states, “The food additive aspartame may be safely used in food”.


Magnuson BA, et al. (2007). Aspartame: a safety evaluation based on current use levels, regulations, and toxicological and epidemiological studies. Crit Rev Toxicol. 37(8):629-727.

Schernhammer, et al. (2012). Consumption of artificial sweetener and sugar-containing soda and risk of lymphoma and leukemia in men and women. Am J Clin Nutr. 96(6):1419-28.


Drink Diet Soda, Gain More Weight?

I know the concept seems counterintuitive: drink more diet soda, gain more weight. However, there has been a media buzz revolving research studies which indicate just that. These artificially sweetened, zero-calorie beverages are marketed as a way to consume less liquid calories, resulting in an energy deficit and thus weight loss. The FDA recognizes stevia, aspartame (Equal), sucralose (Splenda), and other no-calorie sweeteners as safe for the general population to consume.

In addition, food products containing artificial sweeteners has been on the rise over the past 20 years. Know what else has been on the rise? America’s rates of obesity. Are the two linked? I’m not so sure.

Source: Yang Q. Gain weight by “going diet?” Artificial sweeteners and the neurobiology of sugar cravings. Yale J Biol Med. 2010 June; 83(2): 101–108.

Now I’ll be completely honest here, I’m not afraid to admit I absolutely love an ice-cold glass of (fountain) Diet Coke/Pepsi every now and then (or perhaps more often than I care to admit). I’ve also had a few of my peers ask me about this diet soda-weight gain dilemma as well. So I thought it made perfect sense for a food blogger, such as myself, to delve into the sticky and sugary research to find the “truth” behind these claims.

However, when I began my literature search, the articles that supported this claim were only rat studies and human observational studies. For the most part, most large health organizations do not feel that these research studies are strong enough evidence to support the conclusion that diet soda can lead to weight gain.

The Rat Studies

In a 2008 article by Swithers and Davidson, 27 rats were randomly assigned to three diet treatment groups for 5 weeks. A control group, a group that consumed yogurt sweetened with glucose for half of the days, and a group that consumed yogurt whose sweetness alternated between glucose and saccharin for half of the days. Therefore, these two groups of mice were consuming the same number of calories, but with differing amounts of prolonged sweetness. Results found that rats gained significantly more weight and gained significantly more fat mass when they received the artificially sweetened yogurt.

There were a few more studies very similar to this one conducted by the same researchers on rats with different artificially flavored colas, puddings, etc…all revealing similar results.

So what did these studies tell us? They indicate that sweetness was associated with weight gain in rats, even when the “sweetness” was coming from a no-calorie sweetener.

These results are very intriguing because they support the link between artificial sweeteners and weight gain. But I have two problems with this study. One is that the test subjects are rats. It is difficult to compare a rat’s food intake to a human’s because, let’s face it, us humans tend to have more complicated reasons for what and how much we eat. Number two, the sample size is extremely small with only 8-10 rats per experimental group, which doesn’t tell us a whole lot.

The Human Observational Studies

An observational study of over 5,000 participants in San Antonio, Texas followed subjects for 7-8 years. Results found that, not only was artificially sweetened beverages associated with weight gain, but that the more people consumed the more weight they gained (shown in the graphs below).

How Much Is Too Much?

The upper limits of how much non nutritive sweeteners are deemed “safe” for the general population is surprisingly very high.

In a 2009 article from the American Journal of Clinical Nutrition, authors reported common zero-calorie sweeteners and their Acceptable Daily Intakes (ADI), presented in the chart below.  What do these numbers actually mean in terms of real food?

For aspartame, consumers would need to drink upwards of 18-19 cans of diet soda per day in order to reach the ADI, 8-9 sweetener packets for saccharin, and 6 cans of diet soda for sucralose.

Maybe We’re Just Looking for an Excuse?…

This same article looked at dozens of studies relating to the topic of artificial sweeteners, and the authors concluded that there wasn’t enough substantial evidence to link nonnutritive sweeteners with increased appetite and weight gain.

In addition, The Academy of Nutrition and Dietetics released a position paper this year which encourages the use of zero-calorie sweeteners as an aid in weight loss along with a reduced calorie, healthy diet. The Academy also made the conclusion that artificially sweetened beverages are not associated with poor appetite control or weight gain. The paper does state, however, that some of the research may be limited and more research may be needed. I’d have to agree with that. I would like to see many double-blind, randomized control studies which directly proposes an intervention on humans as opposed to just retrospective, observational, and animal studies.

That being said, after looking into some of the literature I still find it hard to completely associate diet sodas with weight gain. Even though the obesity epidemic is on the rise, artificial sweeteners can not be to blame when there are (literally hundreds of) other contributing factors as to why people are gaining more weight. For example, individuals may be choosing more higher calorie, higher-fat foods in conjunction with their diet sodas. For example, have you ever been in line at McDonald’s and seen someone order a Big Mac and a Diet Coke? I highly doubt it’s the Diet Coke adding inches to their waist line…

So in my opinion, if you feel the need to crack open a fizzy can of diet soda…at least it’s better than drinking regular soda which has an extra 140 calories per can. That’s a plus, right? And anyways, I’m more worried about artificial sweeteners being associated with a higher risk of cancer…but that story’s for another blog post some other time.