Which Diet Sodas Do Not Contain Aspartame?

Sometimes you want something with a bit more pizazz than water — like a diet soda. But if you have a rare hereditary disorder known as phenylketonuria (PKU), you need to limit your intake of phenylalanine, found in aspartame.

Fortunately, there are some diet sodas without aspartame.

Aspartame is a sugar substitute about 200 times sweeter than table sugar, so just a small amount is needed to sweeten foods or beverages.

Although it contains 4 calories per gram — the same number of calories in sugar — far less is needed to achieve sweetness, according to the International Food Information Council Foundation. So, it adds negligible calories to food.

It's one of the most popular artificial sweeteners, according to the University of Alabama at Birmingham. Aspartame is composed of aspartic acid and phenylalanine, two amino acids.

The U.S. Food and Drug Administration (FDA) has regulated the use of aspartame since 1974 and approved it as a general-purpose sweetener in 1996.

The acceptable daily intake for aspartame established by the FDA is 50 milligrams per kilogram of body weight, per day. This means a person who weighs 180 pounds can safely take in 4,050 milligrams of the artificial sweetener — or about 20 cans of diet soda — every day.

Aspartame is not safe for some people, though. A hereditary disorder called PKU requires you strictly limit your intake of phenylalanine, one of the components of aspartame. Always choose diet drinks without aspartame if you have this condition.

The amino acids phenylalanine and aspartic acid are present in natural foods, however, so aspartame isn't the only source. In fact, it's been found that one cup of cow's milk has 0.70 milligrams of aspartic acid, per an October 2021 study in ‌Foods,‌ which could be more than some drinks sweetened with aspartame.

A possible link between aspartame and cancer has troubled researchers and consumers for decades.

In July 2023, the World Health Organization reclassified aspartame as "possibly carcinogenic to humans" with "limited evidence," but stressed occasional diet sodas are not cause for major concern. The WHO deems 40 milligrams per kilogram of body weight a safe amount of aspartame per day.

The FDA disagrees that the limited evidence points to human cancer risk, pointing to research like an April 2019 meta-analysis in ‌Regulatory Toxicology and Pharmacology,‌ which found no link between low- and no-calorie sweeteners and beverages to increased cancer risk in humans.

More research is needed on other potential health concerns of aspartame, too.

A June 2018 paper in ‌Nutritional Neuroscience‌ found aspartame has been linked to behavioral and cognitive problems — such as headaches, irritable mood, depression and insomnia. The researchers advise aspartame be approached with caution and that more research about the effects of aspartame on brain health is needed.

A September 2017 review in ‌Nutrition Journal‌ noted there are numerous evidence gaps related to the health effects of nonnutritive sweeteners, including aspartame, so more research is necessary to affirm their safety.

Reduced and no-sugar versions of drinks provide a way to cut back on sugar without having to give up the beverages you enjoy. However, some diet sodas can hurt your stomach, causing gas and bloating.

So if you choose to avoid aspartame-containing drinks, you do have some options.

From Coca-Cola, for example, Diet Coke with Splenda or Coca-Cola Life are options for diet soda without aspartame. Splenda is an artificial sweetener made from sugar. The chemical structure is altered so much of it passes through your body undigested and unabsorbed.

Coca-Cola Life is sweetened with a blend of cane sugar and stevia leaf extract. Stevia is a naturally sweet plant that can be used to offer noncaloric sweetening. Coca-Cola Life has 35 percent fewer calories than traditional Coke and less added sugar.

Aspartame is still present in other Coca-Cola products, including Diet Coke and Coca-Cola Zero Sugar. Other diet sodas from Pepsi, including Diet Pepsi and Pepsi Zero Sugar contain aspartame, too.

Other soda manufacturers offer aspartame-free diet sodas that can satisfy your desire for a bubbly drink without the artificial sweetener and still no calories. Zevia, for example, uses stevia leaf extract to sweeten all of their soda products. Flavors include traditional cola, but also fruit options such as black cherry and orange as well as ginger ale, root beer and cream varieties.

Hansen's diet sodas are sweetened with sucralose and ace-K and contain no aspartame. Hansen's flavors include cola, vanilla, pomegranate, strawberry and ginger ale, among others.