The Truth About Aspartame Side Effects

Medically reviewed by Judith Marcin, MD on August 17, 2017Written by The Healthline Editorial Team

The aspartame controversy

Aspartame is one of the most popular artificial sweeteners available on the market. In fact, chances are good that you or someone you know has consumed an aspartame-containing diet soda within the past 24 hours. In 2010, one-fifth of all Americans drank a diet soda on any given day, according to the Centers for Disease Control and Prevention.

While the sweetener remains popular, it’s also faced controversy in recent years. Many opponents have claimed that aspartame is actually bad for your health. There are also claims about long-term repercussions of aspartame consumption.

Unfortunately, while extensive tests have been conducted on aspartame, there’s no consensus as to whether aspartame is “bad” for you.

What is aspartame?

Aspartame is sold under the brand names NutraSweet and Equal. It’s also used widely in packaged products — especially those labeled as “diet” foods.

The ingredients of aspartame are aspartic acid and phenylalanine. Both are naturally occurring amino acids. Aspartic acid is produced by your body and phenylalanine is an essential amino acid that you get from food.

When your body processes aspartame, part of it is broken down into methanol. Although toxic in large quantities, small quantities of methanol aren’t toxic. It’s naturally produced by the body and is also found in fruit, fruit juice, fermented beverages, and some vegetables.

The amount of methanol resulting from the breakdown of aspartame is low. In fact, it’s far lower than the amount found in many common foods.

Aspartame approvals

A number of regulatory agencies and health-related organizations have weighed in favorably on aspartame. It’s gained approval from the:

  • U.S. Food and Drug Administration (FDA)
  • United Nations Food and Agriculture Organization
  • World Health Organization
  • American Heart Association
  • American Dietetic Association

In 2013, the European Food Safety Authority (EFSA) concluded a review of more than 600 datasets from aspartame studies. It found no reason to remove aspartame from the market. The review reported no safety concerns associated with normal or increased intake.

At the same time, artificial sweeteners have a long history of controversy. Aspartame was developed around the time the FDA banned the artificial sweeteners cyclamate (Sucaryl) and saccharin (Sweet’N Low). Lab tests showed that massive doses of these two compounds caused cancer and other disorders in laboratory animals.

While aspartame is indeed approved by the FDA, the consumer advocate organization Center for Science in the Public Interest has cited numerous studies that suggest problems with the sweetener, including a study by the Harvard School of Public Health.

In 2000, the National Institutes of Health decided saccharin could be removed from the list of cancer-causing substances. Though cyclamate is available in more than 50 countries, it’s not sold in the United States.

Products with aspartame

Whenever a product is labeled “sugar-free,” that usually means it has an artificial sweetener in place of sugar. While not all sugar-free products contain aspartame, it’s still one of the most popular sweeteners. It’s widely available in a number of packaged goods.

Some examples of aspartame-containing products include:

  • diet soda
  • sugar-free ice cream
  • reduced-calorie fruit juice
  • gum
  • yogurt
  • sugarless candy

Using other sweeteners can help you limit your aspartame intake. However, if you want to avoid aspartame altogether, you’ll also need to make sure to look out for it in packaged goods. Aspartame is most often labeled as containing phenylalanine.

Aspartame side effects

According to the American Cancer Society, aspartame is approximately 200 times sweeter than sugar. So only a very small amount is needed to give food and beverages a sweet flavor. The acceptable daily intake (ADI) recommendations from the FDA and EFSA are:

  • FDA: 50 milligrams per kilogram of body weight
  • EFSA: 40 milligrams per kilogram of body weight

A can of diet soda contains about 185 milligrams of aspartame. A 150-pound (68-kilogram) person would have to drink more than 18 cans of soda a day to exceed the FDA daily intake. Alternately, they’d need nearly 15 cans to exceed the EFSA recommendation.

However, people who have a condition called phenylketonuria (PKU) shouldn’t use aspartame. People who are taking medications for schizophrenia should also avoid aspartame.


People with PKU have too much phenylalanine in their blood. Phenylalanine is an essential amino acid found in protein sources such as meat, fish, eggs, and dairy products. It’s also one of the two ingredients of aspartame.

People with this condition aren’t able to properly process phenylalanine. If you have this condition, aspartame is highly toxic.

Tardive dyskinesia

Tardive dyskinesia (TD) is thought to be a side effect of some schizophrenia medications. The phenylalanine in aspartame may precipitate the uncontrolled muscle movements of TD.

Anti-aspartame activists claim there’s a link between aspartame and a multitude of ailments, including:

  • cancer
  • seizures
  • headaches
  • depression
  • attention deficit hyperactivity disorder (ADHD)
  • dizziness
  • weight gain
  • birth defects
  • lupus
  • Alzheimer’s disease
  • multiple sclerosis (MS)

However, there’s insufficient evidence to support a connection between these ailments and aspartame.

Aspartame’s effects on diabetes and weight loss

When it comes to diabetes and weight loss, one of the first steps many people take is to cut empty calories from their diets. This often includes sugar.

Aspartame has both pros and cons when considering diabetes and obesity. First, the Mayo Clinic states that, in general, artificial sweeteners may be beneficial for those with diabetes. Still, this doesn’t necessarily mean that aspartame is the best sweetener of choice — you should ask your doctor first.

Sweeteners may also help weight loss efforts, but this is usually only the case if you consume a lot of sugar-containing products before trying to lose weight. Switching from sugary products to those containing artificial sweeteners may also reduce the risk of cavities and tooth decay.

According to a 2014 PLoS One study, rats that were fed aspartame had lower body masses overall. One caveat to the results was that these same rats also had more gut bacteria as well as increased blood sugar. This increase in blood glucose was also linked to insulin resistance.

Natural alternatives to aspartame

The controversy over aspartame continues. Available evidence doesn’t suggest long-term negative effects, but research is ongoing. Before you switch back to sugar (which is high in calories and has no nutritional value), you can consider natural alternatives to aspartame. You may try sweetening foods and beverages with:

While such products are indeed more “natural” compared to artificial versions like aspartame, you should still consume these alternatives in limited quantities.

Like sugar, natural alternatives to aspartame can contain a lot of calories with little to no nutritional value.

Aspartame’s outlook

Public concern over aspartame remains alive and well today. Scientific research hasn’t shown any consistent proof of harm, thereby leading to acceptance for everyday use.

Due to heavy criticism, many people have taken steps to avoid artificial sweeteners altogether. Still, the consumption of aspartame by people conscious about their sugar intake continues to soar.

When it comes to aspartame, your best bet — as with sugar and other sweeteners — is to consume in limited amounts.

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