Is Aspartame Bad for You? Side Effects, Dangers, Products & Alternatives

Few food additives have been studied with such scrutiny, or with more controversy, as aspartame. Proponents of diet drinks claim that no adverse effects have been proven and that aspartame-laced products contribute to weight loss.

On the other side of the coin, a large community of health-conscious, anti-aspartame health practitioners and consumers are convinced that the U.S. Food and Drug Administration has turned a blind eye to one of the most dangerous food additives ever discovered.

In fact, aspartame may be one of the worst artificial sweeteners you can ingest and has been associated with dozens of potential health risks.

The sweetener industry received a blow when a major study, released in July 2017, connected aspartame to an increased risk of heart disease and increased body mass index. Far from the small studies that are sometimes dismissed, this review included a total of almost 407,000 individuals with a median 10-year follow-up.

Researchers discovered that there were not only zero benefits from consuming “diet” foods and drinks containing these artificial sweeteners (known as “non-nutritive sweeteners,” since they offer no calories), but they were associated with “increases in weight and waist circumference, and higher incidence of obesity, hypertension, metabolic syndrome, type 2 diabetes and cardiovascular events.”

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Of course, a few smaller cohort studies did find weight loss to be a benefit, but as is the norm for aspartame research, those were sponsored by industries benefiting from positive outcomes.

Do aspartame-sweetened products help you lose weight? No.

Is aspartame safe? No.

Is aspartame harmful to the body? Yes.

Let’s explore more about this dangerous food additive, how it came about and why you should stay away from it.

What is aspartame?

To understand why aspartame causes side effects, it’s important to first explain what it is and how it metabolizes when you drink or eat it.

Aspartame is an artificial sweetener, also referred to as acesulfame potassium (K), AminoSweet®, Neotame®, Equal®, NutraSweet®, Blue Zero Calorie Sweetener Packets™, Advantame®, NutraSweet New Pink®, Canderel®, Pal Sweet Diet® and AminoSweet®. It’s used in a variety of food and wellness products, like diet soda, gum, candy and vitamin supplements.

Almost immediately upon consuming aspartame, it breaks down into three chemical compounds: phenylalanine, aspartic acid and methanol.

Those first two components are amino acids. Methanol is known as “wood alcohol” and toxic in large doses, and while the amount of methanol in one can of diet soda is low, it remains dangerous when consumed in aspartame.

Phenylalanine is an amino acid that can be toxic in high doses but is generally recognized as safe in whole food products. However, when chemically bound to other compounds, like in aspartame, phenylalanine is absorbed almost immediately into the bloodstream rather than slowly via digestion.

Since this amino acid can cross the blood-brain barrier and functions as an excitotoxin when absorbed too quickly, it may potentially conflict with various neuronal processes. Just one diet soda raises the level of phenylalanine in the brain, causing serotonin levels to decrease.

In at least one study, phenylalanine concentrations were higher in people with HIV, sepsis, cancer and those undergoing trauma.

Aspartic acid is a non-essential amino acid. That means your body makes it without having to ingest it.

Normally, aspartic acid (aspartate) is important in the function of the nervous and neuroendocrine systems.

Is aspartame safe?

There is some concern about the way the body metabolizes the two amino acids from aspartame. Because of the way diet soda and other aspartame products are created, the amino acids they contain do not go through the normal process of enzyme breakdown and liberation.

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Instead, they absorb immediately into the bloodstream.

However, the more pressing concern comes from the methanol content in aspartame. Now, it is true that methanol is present in other food products, but in those cases, it is bound to pectin, a fiber commonly found in fruits.

Generally, these bound pectin/methanol compounds are excreted safely through the normal digestive process.

In aspartame, however, methanol is bound (weakly, at that) to the phenylalanine molecule. One or two processes easily break that bond and create what is known as “free methanol.”

In cases where the aspartame product has been kept in a hot environment over 85 degrees Fahrenheit (like a warehouse or hot truck), the bonds decompose before ever entering the body.

Free methanol then converts to formaldehyde, more commonly known as embalming fluid. Both methanol and formaldehyde are carcinogens in and of themselves.

Formaldehyde has the unfortunate ability to cross the blood-brain barrier, one reason it is so detrimental to the body. Eventually, the formaldehyde can also turn into diketopiperazine, another known carcinogen.

Every animal other than humans converts formaldehyde to formic acid, a harmless substance. Humans don’t have the necessary enzyme for that change, which is one possible reason why animal studies don’t always represent the extent to which methanol impacts the body.

This process in humans is called methyl alcohol syndrome.

Safety approvals

Aspartame has been extensively reviewed by health and regulatory organizations worldwide, with multiple agencies deeming it safe for consumption within established limits. Some of the key safety approvals include:

• U.S. Food and Drug Administration (FDA): The FDA first approved aspartame as a tabletop sweetener in 1974 and later expanded its use to a variety of food and beverage products. The agency set an acceptable daily intake (ADI) of 50 milligrams per kilogram (mg/kg) of body weight. Over the years, the FDA has reaffirmed its safety, stating that aspartame is safe for the general population, except for individuals with phenylketonuria, a rare genetic disorder that prevents proper metabolism of phenylalanine, a component of aspartame.
• European Food Safety Authority (EFSA): In a comprehensive 2013 review, EFSA confirmed that aspartame is safe for human consumption when consumed within the established ADI of 40 mg/kg of body weight, a slightly lower limit than that set by the FDA.
• World Health Organization (WHO) and Joint FAO/WHO Expert Committee on Food Additives (JECFA): Both organizations have evaluated aspartame and determined that it is safe when consumed within the recommended ADI.
  Health Canada: The Canadian health authority has also conducted independent safety reviews and supports aspartame’s use within regulatory guidelines.
• Australian and New Zealand Food Standards (FSANZ): After multiple assessments, FSANZ has maintained that aspartame does not pose a health risk to the general population when consumed in moderation.
• Food and Agriculture Organization (FAO) of the United Nations: In collaboration with WHO, the FAO participates in global food additive evaluations, including aspartame, and supports the safety assessments established by JECFA.
• Food Standards Agency (United Kingdom): The U.K.’s Food Standards Agency (FSA) has endorsed the safety of aspartame based on reviews of available scientific evidence and supports its use within the acceptable daily intake.

Despite these approvals, aspartame remains a topic of ongoing research and debate. In 2023, the WHO’s International Agency for Research on Cancer (IARC) classified aspartame as “possibly carcinogenic to humans,” though this classification was based on limited evidence.

At the same time, JECFA reaffirmed that current intake levels do not pose a significant health risk. These findings highlight the importance of continued research to further assess long-term effects.

Despite widespread approval, some researchers and health advocates continue to scrutinize aspartame due to conflicting studies on its potential long-term effects. However, major health organizations, including the American Cancer Society, Academy of Nutrition and Dietetics, American Diabetes Association, American Heart Association, and the National Cancer Institute, have found no conclusive evidence linking aspartame to cancer or other serious health issues when consumed within recommended limits.

Ultimately, while regulatory bodies worldwide maintain that aspartame is safe, individuals with sensitivities or health concerns should consider their own tolerance levels and dietary preferences when consuming products containing this artificial sweetener.

While aspartame has been approved for decades, consumers should remain mindful of their total intake and consider individual health conditions when consuming artificial sweeteners.

Products that contain it

Aspartame is found in more than 6,000 individual products, making it virtually impossible to list them all here. If you consider purchasing any of the following types of items, check the label because you’re likely to find aspartame listed.

The following foods, beverages and medications commonly contain aspartame:

• Diet soda
• Sugar-free breath mints
• Sugar-free (or “no sugar added”) cereals
• Sugar-free (or “no sugar added”) condiments
• Flavored coffee syrups
• Flavored water
• Sugar-free ice cream and/or toppings
• Diet iced tea products
• Low-sugar or sugar-free fruit juices
• Meal replacement shakes/snacks
• “Nutrition” bars
• Sports drinks (especially “sugar-free” varieties)
• Soft candy chews
• Yogurt (sugar-free, fat-free and some drinkable brands)
• Vegetable juice drinks
• Natural fiber laxative
• Fiber oral powder supplements
• Appetite control supplements

Side effects and dangers

While 100 percent of industry-funded research has found that aspartame is safe, 92 percent of studies funded independently have discovered adverse effects.

The Ramazzini Institute, a longtime cancer research center in Italy, has studied aspartame at length. It said in 2014 in the American Journal of Industrial Medicine, “On the basis of the evidence of the potential carcinogenic effects of [aspartame] herein reported, a re-evaluation of the current position of international regulatory agencies must be considered an urgent matter of public health.”

What are the most serious dangers and side effects of aspartame?

1. Potentially increases risk of cancer

For decades, studies have shown the potential carcinogenic qualities of aspartame. The Ramazzini Institute continues to stand behind the results of its multiple studies finding that aspartame is associated with a 300 percent increase in lymphoma/leukemia incidence, even after being dismissed by the European Food Safety Authority.

One reason this 20-year study is so significant is because the rats involved in the research were allowed to die naturally rather than being sacrificed earlier in the experiment. This was to investigate the last two-thirds of the animal life span, often unaccounted for, because cancer occurs in humans most often during this portion of life.

Overall, studies have discovered links between aspartame and the following:

• Liver cancer in mice
• Lung cancer
• Brain cancer
• Breast cancer
• Prostate cancer
• Central nervous system cancers (gliomas, medulloblastomas and meningiomas)

The discovery of the central nervous system cancers seems to be associated with the behaviors of the two amino acids found in aspartame. They are consumed in such large amounts and not broken down in the same fashion as when ingested in other foods, and they have the ability to cross the blood-brain barrier. This allows their “excitotoxicity” to take full effect.

Cancer incidence seems to increase when animals are exposed to aspartame in the womb, underlining the importance for pregnant mothers never to consume aspartame. And formaldehyde, a metabolite of free methanol, is associated with the development of breast, stomach, intestinal, lymphoma and leukemia cancers.

Recent research has explored the potential association between aspartame consumption and cancer risk in humans. Notably, the NutriNet-Santé study, a large-scale prospective cohort study conducted in France, investigated the relationship between artificial sweetener intake, including aspartame, and cancer incidence.

This study observed that higher consumption of artificial sweeteners was associated with an increased risk of overall cancer, particularly breast cancer and obesity-related cancers.

2. Might induce or worsen diabetes

Although doctors often recommend replacing sugary drinks with diet versions for diabetics, aspartame seems to have the opposite effect than hoped. Diet soda consumption is associated with a higher risk of type 2 diabetes as well as metabolic syndrome, a cluster of symptoms indicative of heart disease.

In fact, in a study of over 6,800 individuals of varying ethnicity between 45 and 84 years old, the risk of diabetes was 67 percent higher for people who consumed diet soda daily versus those who did not. It seems, in many cases, that aspartame intake can also aggravate diabetes symptoms, such as diabetic retinopathy and diabetic neuropathy.

Research also has shown that aspartame conflicts with insulin/glucose tolerance, a marker of prediabetes, especially for those who are already obese. One reason this happens may be the way that aspartame alters gut microbiota (healthy bacteria). These changes can induce glucose intolerance in otherwise healthy people.

Another study published in 2018 found that aspartame consumption may impair blood glucose tolerance in individuals with type 2 diabetes, suggesting a potential adverse effect on glycemic control.

3. Could increase risk of heart disease and stroke

Aspartame intake is associated with metabolic syndrome. This cluster of conditions includes high blood pressure, high blood sugar, excess belly fat and high cholesterol/triglyceride levels.

It marks a dramatic increase in the risk for heart disease, stroke and diabetes.

Research from Purdue University in 2013 found that frequent consumption of artificial sweeteners, including aspartame, sucralose (Splenda®) and saccharin, was associated with weight gain, metabolic syndrome, diabetes and heart disease because of the “metabolic derangements” it seems to cause.

The Northern Manhattan Study focused on the study of stroke and pertinent risk factors. It found a significant increased risk of heart events, even when controlling the study for those with various related diseases, in people who drink diet soft drinks each day.

The same link was not discovered for those drinking regular soda.

A large-scale prospective cohort study investigated the relationship between artificial sweetener intake and cardiovascular disease risk. The findings indicated that aspartame consumption was associated with an increased risk of cerebrovascular events, such as strokes.

Specifically, higher consumers of aspartame had a hazard ratio of 1.17 (95% confidence interval: 1.03 to 1.33) compared to non-consumers, with incidence rates of 186 and 151 per 100,000 person-years, respectively.

Another study focusing on HIV-infected participants found that aspartame intake was significantly associated with an increased coronary plaque burden. This association suggests that aspartame consumption may contribute to cardiovascular disease risk in this population.

The study also noted links between aspartame intake and markers of inflammation and immune activation, which could play a role in atherogenesis.

Research from the Framingham Heart Study Offspring cohort, meanwhile, examined the consumption of artificially sweetened beverages and their association with stroke and dementia risks. The study concluded that higher intake of these beverages was linked to an increased risk of ischemic stroke and all-cause dementia.

While the study did not isolate aspartame specifically, it highlights potential concerns regarding artificial sweeteners and cerebrovascular health.

4. May cause nervous system and brain disorders

Since many of the major complaints about aspartame are neurologic in nature, particular attention has been given to the way it affects the brain and neurological system.

Neurosurgeon Russell L. Blaylock released a book in 1998 called “Excitotoxins: The Taste That Kills,” detailing his research on aspartame and its relation to brain tumors, cell damage, and conditions like Alzheimer’s and Parkinson’s disease. He attributed these effects to the way the compounds in aspartame overstimulate neurons.

Research at the University of North Dakota’s Department of Nursing found an increase in irritation, more depressive behavior and a decline in spatial orientation in people consuming a “high-aspartame diet.” These “high” aspartame levels were actually about half of what the maximum acceptable daily intake values are, according to the FDA.

Research also has indicated that aspartame consumption can elevate levels of phenylalanine and aspartic acid in the brain, which may be associated with neurophysiological symptoms such as headaches, seizures, migraines, mood disturbances, anxiety, depression and insomnia.

Another double-blind study involving individuals with mood disorders reported severe reactions to aspartame consumption, leading to the early termination of the study. This suggests that individuals with mood disorders may be particularly sensitive to aspartame’s effects.

There has also been at least one finding published in Neurology that aspartame intake exacerbated the number of EEG spike waves in children suffering absence seizures.

5. Could worsen or trigger mood disorders

Closely related to its impact on neurological decline, aspartame may also be closely tied to the development of certain mental disorders, especially depression. Ingesting aspartame could potentially lead to a decline in learning and emotional function.

Drinking diet beverages has been linked to depression more than once, including in one study of almost 264,000 participants over 10 years. Researchers found that those who drank more than four cans or cups of diet soda each day were between 30 percent and 38 percent more likely to develop depression, while coffee drinkers were 10 percent less likely to be diagnosed with depression.

A famous study was conducted in 1993 to discover a correlation between mood disorders and aspartame in those with or without depression diagnoses. Before it could be completed, the Institutional Review Board had to halt the study because the participants who had a history of depression experienced such severe negative reactions that it led the department to discourage anyone with history of mood problems from ingesting aspartame because of their suggested high sensitivity to it.

6. Possibly contributes to fibromyalgia

Millions of people in the U.S. suffer from the chronic pain disorder known as fibromyalgia. The causes and cure are still unknown, but one small study examined fibromyalgia patients who had been struggling for years to find effective treatments.

The study found that eliminating aspartame and MSG (two of the most common dietary excitotoxins) resulted in a complete or nearly complete resolution of all symptoms within a few months. The symptoms returned upon ingestion of either substance.

Several other human studies have investigated the potential link between aspartame consumption and fibromyalgia symptoms as well.

One study reported two cases where patients experienced chronic pain diagnosed as fibromyalgia, which resolved upon eliminating aspartame from their diets. A 50-year-old woman had widespread pain and fatigue for over 10 years. Her symptoms disappeared during a vacation when she inadvertently stopped consuming aspartame and reappeared upon resuming its intake.

Similarly, a 43-year-old man suffered bilateral forearm, wrist, hand and cervical pain for three years, which resolved completely after discontinuing aspartame.

Another study examined the impact of dietary glutamate, including aspartame, on fibromyalgia symptoms. Participants followed a diet eliminating excitotoxins like MSG and aspartame for four weeks.

Among the 37 participants who completed the diet, 84% reported over 30% symptom improvement. Subsequent challenges with MSG led to a significant return of symptoms, suggesting dietary glutamate may contribute to fibromyalgia symptoms in some patients.

7. Associated with weight gain

Aspartame studies have found the non-nutritive sweetener was actually linked with weight gain rather than the weight loss it promises. (After all, drinks containing aspartame literally carry the label “diet.”)

For instance, one review indicated that artificial sweeteners could alter the host microbiome, decrease satiety and disrupt glucose homeostasis, potentially leading to increased caloric consumption and weight gain.

There are a few suggested reasons aspartame does not lead to weight loss. For one, consuming non-nutritive sweeteners (sweet substances that do not have calories) does nothing for the more sweet foods.

While eating sugar has that same effect, actual sugar has the benefit of providing caloric feedback, the “food reward” your body understands to mean it should stop eating. Aspartame, however, does the opposite. It encourages cravings and sweets dependence, all without the caloric feedback you need to control your intake.

This, in turn, results in eating more non-nutritious foods and drinks.

A 2014 experiment actually postulated that drinking diet beverages influences psychological processes that might cause a person to increase overall caloric intake.

8. Might cause premature menstruation

In a newer side of aspartame research, three U.S. universities studied young girls for 10 years to track growth and hormonal changes as well as lifestyle and diet. They found that drinking caffeinated soft drinks, particularly diet drinks that contain aspartame, was associated with early development of menstrual cycles.

Why does this matter? Because the long-term risks of early puberty include breast cancer, HPV, heart disease, diabetes and all-cause mortality.

9. Linked to development of autism

Another reason to avoid this sweetener is because it has been linked to the development of autism in children. In the journal Medical Hypotheses, researchers discussed a study in which women who had been exposed to dietary methanol (found in aspartame) were significantly more likely to give birth to children who developed autism.

In addition, a case-control study investigated the impact of daily early-life exposure to diet soda and aspartame on autism risk. The study involved 235 children with autism spectrum disorder (ASD) and 121 neurotypical controls.

Findings indicated that males exposed to at least one diet soda or 177 mg of aspartame daily during gestation or early life had over three times higher odds of developing autism compared to unexposed males. Specifically, the odds ratio (OR) for autism was 3.1 (95% confidence interval [CI]: 1.02, 9.7), and for non-regressive autism, the OR was 3.5 (95% CI: 1.1, 11.1).

However, subsequent commentary raised concerns about the biological plausibility and methodological aspects of the aforementioned study. The authors highlighted potential issues that could affect the validity of the findings, suggesting that more rigorous research is needed to establish a clear link between aspartame exposure and autism development.

10. May increase risk of kidney disease

In people with initially healthy kidney function, drinking diet sodas laden with aspartame may be associated with a 30 percent greater drop in kidney function than those who do not drink diet sodas. This research was conducted over 20 years and included over 3,000 women.

A meta-analysis also assessed the relationship between artificially sweetened beverage consumption and(chronic kidney disease (CKD) risk. The pooled relative risk for high versus low consumption was 1.40 (95% CI: 0.65-3.02) across three studies involving 19,995 participants.

Although the association did not reach statistical significance, a dose-response analysis indicated that consuming more than seven servings per week of sugar or artificially sweetened beverages was linked to an increased risk of CKD.

Another study examined the effects of aspartame ingestion on calcium and oxalate metabolism in seven healthy subjects. The findings revealed that aspartame intake led to an 86% increase in urinary calcium excretion.

This hypercalciuria could potentially contribute to kidney stone formation and impair renal function.

While the overall research is not necessarily conclusive, with many studies conducted on animals or in lab settings, this artificial sweetener has been associated in one form or another with a long list of health issues, including:

• Alzheimer’s disease
• Allergies
• Altered gut bacteria
• Attention deficit hyperactivity disorder (ADHD)
• Behavioral and cognitive effects
• Birth defects
• Cancer
• Chronic kidney disease
• Depression
• Dizziness
• Headaches
• Heart disease
• High blood pressure
• Increased appetite and food intake
• Lupus
• Multiple sclerosis (MS)
• Poor blood glucose control
• Preterm delivery
• Seizures
• Skin problems
• Sweet cravings
• Type 2 diabetes
• Weight gain

Natural alternatives

What is the safest artificial sweetener to use? In reality, any synthetic, artificial food isn’t the best choice for your body and health.

However, there are a few natural alternatives to aspartame that won’t have the same devastating health effects.

One of the best natural sweeteners is stevia. The rule for sweeteners is always in moderation.

While the following three can even provide health benefits, it’s best to limit your intake of sweets overall and tend more toward whole foods like vegetables, fruits and organic meat:

• Stevia: The stevia plant has been around for a millennia and a half in parts of South America and is about 200 times sweeter than sugar, gram for gram. When using stevia, make sure to avoid dangerous altered stevia blends (which often contain very little stevia) and stick to pure, organic stevia.
• Raw Honey: Raw, organic honey has been known to help counter the effects of certain allergies as well as help manage weight, promote sleep and fight oxidative stress.
• Monk Fruit: This fruit-based sweetener has no calories but is between 300-400 times sweeter than sugar. There is evidence that it may help lower risk of diabetes as well as combat infection.

Other healthier natural sweeteners include:

• dates
• coconut sugar
• maple syrup
• blackstrap molasses
• balsamic glaze
• banana puree
• brown rice syrup
• real fruit jam
• allulose

Final thoughts

• Aspartame is a non-nutritive sweetener that has been around for a few decades and is found often in diet sodas, like Diet Coke or Diet Pepsi, as well as sugar-free and “no sugar added” food products.
• It breaks down into two amino acids, phenylalanine and aspartic acid, as well as methanol (which converts to formaldehyde and diketopiperazine). The last three of this list are known carcinogens.
• The methanol and formaldehyde are especially dangerous to humans because of the way they metabolize in the body, coupled with the fact that we do not have the necessary enzyme to convert formaldehyde to a less dangerous substance, as most animals do.
• Many studies have been conducted on aspartame dangers and have found that it is linked with a large number of health conditions, ranging from headaches to cancer and diabetes in both animal and human studies.
• Drinking or eating aspartame products is especially dangerous for mothers and young children because of the way it affects behaviors and conditions later in life.
• If you are experiencing conditions that could potentially be related to aspartame, it’s probably a good idea to abstain entirely and see if any symptoms alleviate on their own. This should be done under the supervision of a doctor.