Aspartame is a widely used, low-calorie, artificial sweetener and one of the most popular sugar substitutes in low-calorie food and drinks, including diet sodas. It is also a component of some medications.

Aspartame is available in the United States under the brand names Nutrasweet and Equal.

Despite its extensive use and popularity, aspartame has become a source of controversy in recent years with several studies claiming the sweetener has adverse side effects.

In this article, we look at the most recent evidence on the safety of aspartame. We also investigate how it might affect weight, appetite, and certain medical conditions.

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In the United States, aspartame is marketed as Equal and Nutrasweet.

The U.S. Food and Drug Administration (FDA) approved aspartame for use in food and drink back in 1981.

Agencies in Europe, Canada, and many other countries also approve its use. Furthermore, the following authorities endorse it:

  • World Health Organization
  • United Nations Food and Agriculture Organization
  • American Heart Association
  • American Dietetic Association

In 2013, the European Food Safety Authority (EFSA) conducted a review of hundreds of studies looking into the effects of aspartame.

The EFSA ruled aspartame safe for human consumption and set an acceptable daily intake or ADI of aspartame at 40 milligrams (mg) per kilogram (kg) of body weight.

The EFSA's ADI for aspartame is 10 mg lower than the amount the FDA consider safe.

However, the amounts set by both the EFSA and the FDA are far more than most people consume in a day.

A can of diet soda, for example, contains only about 190 mg of aspartame. A person would have to consume more than 19 cans of soda to reach the ADI limits.

Aspartame contains 4 calories per gram (g), similar to sugar. It is, however, around 200 times sweeter than sugar.

This means that only a tiny amount of aspartame is necessary to sweeten foods and drinks. For this reason, people often use it in weight-loss diets.

By contrast, a 2017 review of the latest research found no evidence that the low-calorie sweeteners aspartame, sucralose, and stevioside, were effective for weight management.

Some studies monitored participants over several years. They found a link between an increased body weight and waist circumference and a regular intake of these sweeteners.

Participants in some studies showed an increased body mass index (BMI) as well. BMI can help to assess if a person has a healthy weight or not. People with a high BMI may be more likely to develop metabolic disease.

Furthermore, the 2017 review found studies that suggested those who consumed sweeteners regularly might be at greater risk of developing heart disease, diabetes, and stroke.

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Studies suggest that sweeteners may increase appetite.

One way aspartame and other nonnutritive sweeteners may affect body weight is by increasing people's appetite, which may lead to a higher food consumption.

A 2013 review published in Trends in Endocrinology and Metabolism cites several animal studies that report a link between regular intake of nonnutritive sweeteners and increased food intake.

The review suggests that sweeteners may increase appetite by disrupting the signaling process that usually occurs when a person eats foods with more calories.

Sweet tastes typically signal to the body that food is entering the gut. The body then expects to receive calories and signals when eating should stop by making a person feel full or satiated.

A person experiences the same sweet taste when they consume sweeteners, but the body receives fewer calories than it might otherwise expect to.

If this happens regularly, according to the theory, the body unlearns the association between sweet tastes and calories. This reversal means that high-calorie foods will no longer trigger feelings of fullness. This may lead to overeating.

Further research on human participants might lead to a better understanding of the link between aspartame consumption and appetite control.

The same process that may disrupt appetite control could also predispose a person to certain metabolic diseases, such as type 2 diabetes, according to the 2013 review.

Because the body no longer expects calorie intake in response to sweet tastes, it may be ill-equipped to deal with dietary sugars when they do arrive in the gut, according to this view.

A later review from 2016 further discusses the link between low-calorie sweeteners and metabolic disease. It suggests that regular, long-term intake of sweeteners may disrupt the balance and diversity of bacteria living within the gut.

Animal studies show that this type of disruption can result in glucose intolerance, which is a known risk factor for type 2 diabetes.

A study from 2016 investigated the effects of certain sugars and sweeteners on people's glucose tolerance.

Researchers found a link between aspartame use and greater glucose intolerance among those with obesity. None of the sugars and sweeteners tested, however, had any negative effect on people of a healthy weight.

These studies suggest that regular intake of aspartame could increase the risk of glucose intolerance, particularly in people who may already be overweight.

News reports over the last few decades have claimed that aspartame causes or increases the risk of:

There is insufficient scientific evidence, however, to confirm or refute claims of aspartame's involvement in any of the above.

People with the following conditions should avoid aspartame:

Phenylketonuria

Phenylketonuria (PKU) is an inherited metabolic disorder that increases levels of the essential amino acid known as phenylalanine in the blood.

Because people with PKU are unable to metabolize phenylalanine properly, they should avoid or limit its intake from food and drink.

Phenylalanine is one of three compounds that make up aspartame. However, aspartame provides significantly lower amounts of phenylalanine than everyday food sources, such as meat, fish, eggs, and dairy products.

People with PKU need to monitor all dietary sources of phenylalanine to avoid toxic levels. Because of this, all products containing phenylalanine in the U.S. carry a label.

Tardive dyskinesia

Tardive dyskinesia or TD is a neurological disorder that causes sudden, uncontrollable jerking movements of the face and body. It most often results from long-term use of antipsychotic medications.

Some research on causes of TD suggests phenylalanine may trigger the muscle movements that characterize TD.

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Diet soda may contain aspartame.

Many foods and drinks that carry the label "sugar-free" may contain some form of artificial sweetener.

The following are likely to contain aspartame:

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

Drug manufacturers also use aspartame to make certain medications more palatable.

Examples of medications that may include aspartame are laxatives and chewable vitamin supplements.

Those wishing to limit their intake of aspartame can try an alternative natural sweetener from the list below:

  • honey
  • maple syrup
  • agave nectar
  • stevia leaves
  • molasses

Although the above options may be preferable to aspartame, people should only use them in small amounts.

They can be high in calories, similarly to sugar, with little or no nutritional value. Excessive amounts can also cause tooth decay.

There is still much controversy surrounding the safety of aspartame, despite approval from authorities around the world.

Recent scientific evidence suggests that regular, long-term intake of aspartame and other low-calorie sweeteners may have negative effects on weight management, but more rigorous research is necessary to confirm these findings.

There is little evidence to suggest that occasional consumption of aspartame is detrimental to health for those who are of a healthy weight.

For those with obesity, however, regular consumption of low-calorie sweeteners may increase the risk of metabolic diseases, including type 2 diabetes.