Aspartame Is Not “Safe”: A Scientific Review

From time to time, the conversation of artificial sugars arises. On one end, people believe if something is ‘approved’ by the FDA, it is entirely safe, and on the other end, people believe in only consuming sweeteners from natural sources. However, I have a different standpoint: I agree with the latter of the two statements, but I disagree with its reasoning.

Instead of merely believing natural sweeteners are the best, it is also essential to understand why artificial sweeteners are harmful. Remember, the FDA allows many chemicals in the American food supply that are banned in Europe; it is all about perspective.

It is also important to note the definition of safe. According to Merriam-Webster, safe is defined as "free from harm or risk." 

In this article, we will review the chemical makeup of one of the most popular artificial sweeteners, aspartame, and examine several studies which give an alternative, yet scientifically backed, perspective on how safe aspartame is. I have defined any medical or scientific terms in [brackets] for your contextual understanding.

Aspartame (aspartylphenylalanine)

According to the Encyclopedia Britannica, aspartame is a synthetic, organic compound of phenylalanine and aspartic acid, 150-200 times the sweetness of sugar, and is not suitable for baking [1]. Its chemical name is aspartylphenylalanine, but I guess aspartame sounds more attractive [1]. While the healthfulness of aspartame is still being discussed for the general population, there are two segments of people who should not have this chemical under any circumstances: People who have phenylketonuria (PKU) or tardive dyskinesia (TD).

Phenylketonuria is an inherited metabolic disorder that results in increased levels of phenylalanine, an ingredient of aspartame, in the blood [2]. Because people with PKU are unable to metabolize phenylalanine, they should not consume aspartame. PKU symptoms include seizures and neurological problems, tremors, stunted growth, hyperactivity, skin conditions, irreversible brain damage and intellectual disabilities within the first few months of life, and behavioral problems and seizures in older children [3].

Tardive dyskinesia is a neurological disorder that causes sudden, uncontrollable jerking movements of the face and body [2]. Some research suggests aspartame can trigger the muscle movements that characterize TD. Other symptoms include sticking your tongue out without you trying, blinking your eyes fast, smack or puckering your lips, and frowning or grunting. There is also another form of TD, which affects your body instead of your face [4]. Those symptoms include wiggling your fingers, tapping your feet, flapping your arms, thrusting your pelvis, or swaying from side-to-side, all without even trying [4].

Now since we have covered the two segments of people who should not have aspartame under any circumstance, let us focus on the rest of the population. We will begin by reviewing a handful of the numerous studies investigating the severe side-effects of ingesting aspartame. I am not going to go super-in-depth into these studies, mainly because I am trying to be as concise as possible, but I will reference each study, so if one intrigues you, you can examine it.

Association with Albuminuria and Kidney Function Decline

A 2011 study investigated the association between sugar and artificially sweetened sodas to the risk of kidney function decline and albuminuria [the presence of albumin in the urine, typically as a symptom of kidney disease]. The study found the consumption of ≥2 servings per day of artificially sweetened (diet) soda was independently associated with 2-fold increased odds for kidney function decline in women [5]. No association was found between these two ailments and sugar soda. The researchers noted while they did not specifically investigate the relationship between aspartame and these ailments, aspartame was one of the two primary artificial sugars that would have been in soda during this time, with the second being saccharin [5].

Aspartame Acts as a Chemical Stressor

In a 2015 study, researchers noted when aspartame is metabolized, or digested, in the gut, it produces three chemicals: the amino acids 1) aspartic acid and 2) phenylalanine and small amounts of 3) methanol [6]. The researchers investigated these chemicals’ association with producing chemical stressors in rats. After the study was conducted, the researchers concluded, “The findings clearly point out that aspartame acts as a chemical stressor because of increased corticosterone level and increased lipid peroxidation and nitric oxide level induce generation of free radicals in serum which may be the reason for variation of cytokine level and finally results in alteration of immune function” [6]. They stated the methanol or formaldehyde produced in the gut resulted by aspartame digestion to be the likely factors [6].

Aspartame Seems to Adversely Affects Spatial Cognition, Insulin Sensitivity

In a 2012 study, researchers investigated the effects of lifetime exposure to aspartame to changes in blood glucose parameters, spatial learning, and memory [7]. The researchers concluded lifetime exposure to aspartame might result in impairment of glucose and insulin balance, together with a reduction in cognitive performance [7]. The researchers also noted this sensitivity was far more significant in males compared to females. The researchers further stated their data supports the previous notion that chronic exposure to aspartame may result in memory deficits [7].

Aspartame Induces Brain Oxidative Stress and Vascular Congestion

In a 2013 study, researchers determined to investigate the effect of long-term intake of aspartame on antioxidant defenses. They concluded, “The results of this experiment indicate that long-term consumption of aspartame leads to an imbalance in the antioxidant/pro-oxidant status in the brain, mainly through the mechanism involving the glutathione-dependent system” [8]. Therefore, the long-term consumption of aspartame caused brain oxidative stress and vascular congestion [8].

Aspartame is Associated with Neurological Dysfunction

In 2007, researchers at the University of Athens, Greece, were determined to investigate aspartame’s effect on acetylcholinesterase (AChE) [an enzyme which is involved with neurotransmitters, in the frontal cortex]. The researchers found after the consumption of 150-200 mg/kg of aspartame, frontal cortex activity was inhibited about 11-29%. Thus, the researchers concluded, “may directly and/or indirectly act on the frontal cortex AChE” [9].

They also noted high doses “remarkably decreased” the enzyme activity, and if these findings are found in humans in future studies, “it may be suggested that cholinergic [relating to or denoting nerve cells in which acetylcholine acts as a neurotransmitter] symptoms are related to the consumption of the above ASP [aspartame] doses” [9].

Aspartame Can Be Converted into Toxic Chemicals

As previously mentioned in one of the above studies, as aspartame is metabolized, one of the chemicals aspartame is methanol. Methanol’s metabolites, a substance produced by a metabolic reaction, are formaldehyde and formate. A 2002 study investigated the cytotoxic effects of methanol, formaldehyde, and formate on dissociated rat thymocytes [a lymphocyte, produced in the thymus, that develops into a T cell] [10]. The researchers found blood levels of the toxin formaldehyde, caused by increases of methanol, were higher in individuals who were administered aspartame [10].

A 2008 study went a step further and investigated the relationship between formaldehyde, aspartame, and migraines and presented a case stating increased levels of formaldehyde caused by aspartame intake has an association with increased risks of migraines [12].

Aspartame is Associated with Cancers

In 2006, researchers conducted a long-term mega-experiment on aspartame. The researchers concluded aspartame causes “an increased incidence of malignant tumor-bearing animals, with a positive significant trend in both sexes,” “an increase in lymphomas-leukemias, with a positive significant trend in both sexes,” “a statistically significant increased incidence, with a positive significant trend, of transitional cell carcinomas of the renal pelvis and ureter in females,” and “an increased incidence of malignant schwannomas of the peripheral nerves, with a positive trend in males” [11]. In experimental testing conditions, aspartame is a “multipotential carcinogenic agent” [11].

Aspartame May be Associated with Mental Disorders

The 2007 study reviewed was entitled, “Direct and indirect cellular effects of aspartame on the brain” and is a very dense study. To review the complete study, see reference [13].

In the 2007 study, researchers proposed “that excessive aspartame ingestion might be involved in the pathogenesis of certain mental disorders (DSM-IV-TR 2000) and also in compromised learning and emotional functioning” [13].

This was mostly due to the long series of complex consequences and chemical reactions that happen in your body as a result of ingesting this chemical.

The researchers concluded, “that the usage of aspartame should be carefully considered as it (and its metabolites) causes detrimental effects, ranging from alterations in concentrations of neurotransmitters to causing infertility. Thus, human health at the macroscopic, microscopic and cellular level is at risk of being destroyed” [13].

Aspartame May Have a Correlation with a Higher Risk of Leukemia

In 2006, researchers found a correlation between aspartame intake and higher serum levels of benzene metabolite, which is associated with various blood disorders and leukemia [14].

Aspartame Has Toxic Effects on Astrocytes and Neurons

In 2013, researchers in Poland investigated aspartame’s metabolites, aspartic acid, phenylalanine, and methanol, and their effect on astrocytes [a neuroglial cell, in the shape of a star, in the brain], and neurons. Even before any research, the scientists noted aspartame as a “highly hazardous compound” which, I guess, highlights the sad truth about the FDA's notion that aspartame is safe [15]. The researchers found aspartame contributed to the formation of glial cells in the brain, which are the primary source of tumors and aspartame may intensify the destruction of neurons [15].


My goal in this article was to inform you of the scientifically backed, alternative view of the safety of aspartylphenylalanine. While the FDA may approve of this chemical, I would never say this chemical is safe because there are indeed severe risks to its consumption. Since these are only a handful of the numerous studies available, I implore you to research more on this topic. I also plan on researching and writing an article on the second, most popular artificial sweetener, sucralose.

If you have any questions about any of our products or about any of the natural sweeteners Healthmasters offers, please call our office at 800.726.1834