Is Aspartame Bad for You?

April 4, 2023

Few food additives have been studied with such scrutiny — or with more controversy — than that of 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 is 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.”

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 vitamins.

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. 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.

Products that Contain It

Aspartame is found in over 6,000 individual products, making it virtually impossible to list them all here. However, I hope that understanding the impact of nutrition on your health makes you an avid label-reader. If you consider purchasing any of the following types of items, check the label — 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 finds that aspartame is safe, 92 percent of studies funded independently discover adverse effects.

The Ramazzini Institute, a longtime cancer research center, has studied aspartame at length. It claimed again 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.

So, 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.

A Ramazzini animal study shows a correlation between aspartame and various cancers to the degree that the organization refers to it as a “multipotential carcinogenic agent,” even in doses well below the legal “acceptable” amounts.

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 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.

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 this study of over 6,800 individuals of varying ethnicity between 45–84 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 shows 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.

An animal study in December 2016 suggests a connection between an interaction between aspartic acid found in aspartame and glucose management. This, again, is exacerbated by the way this amino acid passes the blood-brain barrier. Researchers also discovered behavioral deficits in the subjects.

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.

Like the carcinogenic risks of aspartame, the heart disease risks also seem to rise when animals are exposed to it in the womb. Animals exposed prenatally to aspartame eat more sweet foods in adulthood, are at risk for obesity, and more often have high blood sugar, high LDL cholesterol and high triglycerides.

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 attributes 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 (ADI) values are, according to the FDA. This correlates with a 2014 animal study that found chronic aspartame consumption to be related to a distortion of neuronal function and an uptick in brain cell death in certain regions of the brain. This study was conducted using the FDA-approved ADI value.

For those who also consume MSG (monosodium glutamate, another controversial food additive), these cognitive problems may be even more pronounced. MSG and aspartame exposure drastically drops dopamine and serotonin levels in the brain of mice and cause oxidative stress that can damage brain cells. That’s not the only time it’s been found that aspartame induces oxidative stress and interrupts the body’s ability to fight it with antioxidants. This impact is most significant in cases of long-term aspartame consumption and is associated with memory loss and more in animal studies.

One of the first studies on the subject of aspartame in the brain was conducted by John Olney, the founder of the field of neuroscience known as excitotoxicity, in 1970. He was a longtime opposer to aspartame’s legalization because of his extensive research on the subject. His 1970 publication found that infant mice exposed to aspartame developed brain damage, even when given relatively low doses.

If this holds true in humans at some level, it could help explain why aspartame is linked to an increased risk of stroke and dementia, according to the Framingham Heart Study. 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 drink 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

Over 6 million 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.

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.”) Drinking and eating aspartame products is associated with metabolic syndrome in mice, one feature of which is excess belly fat. It’s pretty clear that aspartame does not help you lose weight. Now the question is: Why?

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. In addition to this interruption of normal biofeedback, a study published in late 2016 conducted on mice found that the phenylalanine in aspartame is an inhibitor of a digestive enzyme that protects against developing metabolic syndrome called “intestinal alkaline phosphatase.”

Thus, not only do diet drinks lead to higher calorie consumption overall, but one of their compounds may actually stop your body’s normal responses that are meant to protect against obesity and other disease risk factors.

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, 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.

10. Increased 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.

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 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 to lower risk of diabetes as well as combat infection.

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.
Many studies have been conducted on aspartame dangers and found that it is linked with a large number of health conditions ranging from headaches to cancer to 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.