Aspartame is a non-nutritive sweetener (NNS). It has not been conclusively linked with any serious side effects or health problems, but people with certain conditions should be careful when ingesting it.

Aspartame is one of the most popular non-nutritive sweeteners (NNS) available on the market. In fact, chances are good that you or someone you know has consumed an aspartame-containing drink within the past 24 hours.

A 2017 study found that in a sample of nearly 17,000 Americans, about 25 percent of children and roughly 41 percent of adults self-reported eating or drinking a food or beverage containing NNS, including but not limited to aspartame.

While aspartame remains popular, it’s also faced controversy in recent years. Many opponents have claimed that consuming aspartame has negative side effects. There are also negative claims about long-term side effects of ingesting aspartame.

Aspartame is sold under the brand names NutraSweet and Equal. It’s also used widely in packaged products — especially those labeled as “diet,” sugar-free, no- or low-calorie, or no-, low- or zero-sugar.

Aspartame is an odorless powder that is white and is approximately 200 times sweeter than sugar. This means that a very small amount is needed to give foods and beverages a sweet flavor.

The ingredients of aspartame are aspartic acid and phenylalanine. Both are naturally occurring amino acids — also know as the “building blocks” of proteins. Aspartic acid is produced naturally by your body, and phenylalanine is an essential amino acid that you get from food.

How is aspartame broken down in the body?

When your body processes aspartame, part of it is broken down into methanol. Consumption of fruit, fruit juice, fermented beverages, and some vegetables also contain or result in methanol production.

A 2015 study suggests that aspartame was the largest source of methanol in the American diet. Methanol is toxic in large quantities, yet smaller amounts may also be concerning when combined with free methanol because of enhanced absorption.

Free methanol is present in some foods and is also created when aspartame is heated. Free methanol consumed regularly may be a problem because it breaks down into formaldehyde, a known carcinogen and neurotoxin, in the body.

However, scientists and expert regulatory groups caution against making overgeneralized conclusions about the relationship between aspartame intake, methanol and formaldehyde production in the body, and consequences for health.

For example, the European Food Safety Authority (EFSA) and Food and Drug Administration (FDA) note that that dietary exposure to methanol and formaldehyde produced from ingesting aspartame does not pose a safety concern.

Other researchers note that consuming tomato juice could result in a 6 times greater methanol production than the aspartame used in zero sugar sodas.

Aspartame is one of the most exhaustively studied NNS in the world. A number of regulatory agencies have confirmed that aspartame and its breakdown products are safe and approved for use in the general population (including infants, children and people who are pregnant or lactating):

Many health-related organizations also note aspartame has not been conclusively linked to any adverse side effects:

In 2013, EFSA was asked to re-evaluate the safety of aspartame, conducting 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. However, a 2019 paper and 2020 paper from the same research group, as well as letter to the editor published in 2020 in the journal Archives of Public Health, question EFSA’s conclusions on the safety of aspartame.

The Scientific Report of the 2015 Dietary Guidelines Advisory Committee also recently reviewed the evidence on aspartame safety ahead of submitting their report to the U.S. Department of Agriculture, and U.S. Department of Health and Human Services (HHS), to provide information for the 2015-2020 Dietary Guidelines for Americans.

The committee agreed with EFSA’s conclusions on aspartame safety for the general population.

Acceptable daily intake levels of aspartame

The acceptable daily intake (ADI) is used as an estimate of the amount of aspartame that can be consumed every day over a persons entire lifetime (the general population, including all age ranges and physical conditions) without any adverse health outcomes or side effects.

The ADI recommendations from the FDA and EFSA for aspartame are:

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

To put this into perspective for a person weighing 150 pounds (or 68 kilograms), the below is what would have to be ingested to meet the FDA ADI:

Whenever a product is labeled “sugar-free,” that usually means it has a NNS 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 foods as well as drinks.

Some examples of aspartame-containing products include:

  • zero sugar soda
  • sugar-free ice cream
  • reduced-calorie fruit juice
  • sugar-free gum
  • reduced sugar ketchup
  • light yogurt
  • no sugar energy bars
  • sugar-free salad dressing
  • sugarless candy

Products containing aspartame must label it on the ingredients panel on the back or side of the product package. But, some food and beverage manufacturers have already begun removing aspartame as an NNU used in their products.

Aspartame has not been conclusively linked with any serious side effects or health problems in the general population. For certain people, products containing aspartame should be avoided due to the potential for harmful side effects to occur.

Phenylketonuria

People who have a condition called phenylketonuria (PKU) shouldn’t ingest products containing aspartame. PKU is a rare genetic disease diagnosed at birth. People with PKU aren’t able to properly process phenylalanine, so it can accumulate to dangerous levels in the body.

A build-up of phenylalanine in the body can lead to a range of negative side effects, including brain damage.

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.

The ADI and safety approvals for aspartame do not apply to people with PKU. Federal labeling regulations require foods, drinks, and medications containing aspartame to have the following warning on the ingredients panel to help people with PKU avoid ingesting a product with aspartame: “PHENYLKETONURICS: CONTAINS PHENYLALANINE.”

Tardive dyskinesia

People who are taking medications for schizophrenia should also avoid aspartame. 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.

Other

The HHS has noted that some additional populations may have problems with aspartame because their body cannot properly break down phenylalanine, including:

  • people with advanced liver disease
  • pregnant women with hyperphenylalanine (high levels of phenylalanine in blood)

There have been a multitude of claims with varying levels of scientific certainty linking aspartame to many side effects and adverse health outcomes, including but not limited to:

Some research reports an increased risk of disease or acceleration of side effects, while others report no negative outcomes linked with aspartame intake. Consistency on the science related to these claims about aspartame could be complicated by the challenges of how research on NNS is done, interpreted, and reported on.

In fact, a 2019 study commissioned by the World Health Organization looked at the relationship between NNS, including aspartame, and several health outcomes in humans, including:

  • body weight
  • blood sugar control
  • oral health
  • eating behavior
  • preference for sweet taste
  • cancer
  • cardiovascular disease
  • kidney disease
  • mood, behavior, neurocognition
  • other adverse side effects

While the researchers didn’t find significant differences between the groups who ingested NNS compared those who didn’t for most of the health outcomes and side effects studied, several limitations existed in their ability to have confidence in the reported results:

  • too few studies found for each health outcome
  • too few research participants in identified studies
  • studies identified were too short in time
  • the methodology and reporting was limited and poor quality
  • potential harms could not be excluded

Given such inconsistency in the scientific literature, and the limited amount of high-quality studies done to-date on any of these health conditions or side effects, research is ongoing to explore if aspartame is linked conclusively and with a strong level of scientific certainty to any of these reported negative outcomes.

Despite aspartame’s widely accepted safety record, many scientists are calling for additional research on the side effects and health outcomes of its ingestion over long-term periods of time, across all life stages, and within different settings.

If you want to avoid products containing aspartame, natural NNS alternatives exist. You may want to try searching for products containing, or sweetening foods and beverages with:

While such products are indeed more “natural” compared to other NNS like aspartame, you should still consume these alternatives in moderation and as directed for use.

Aspartame is one of the most extensively researched substances in the food supply today with decades of scientific work and hundreds of studies completed to-date.

Despite unanimous consensus from global regulatory agencies and health organizations that aspartame consumed in the manner it has been approved for use is safe and has minimal health risks for the general population, public concern on if aspartame has side effects remains alive and well today.

Aspartame may be a helpful solution for certain people and population groups to control calories and added sugar intake when used in moderation as part of a balanced lifestyle. But, additional research is needed to explore aspartame’s potential side effects and adverse impacts on health outcomes, especially with long-term exposure.

If you are a person with PKU or are otherwise instructed by a doctor to manage your dietary phenylalanine intake, you should avoid all products containing aspartame. There are many alternative NNS available.

If you feel you have a sensitivity to aspartame or would like to avoid products with aspartame for personal preference, be sure to thoroughly review the ingredients panel and choose foods or drinks made without aspartame.