Are Artificial Sweeteners Toxic to the Brain?

As sugar’s harmful effects are becoming more widely acknowledged, the consumption of artificially sweetened foods and drinks is increasing. Everyday, we are exposed to artificially sweetened diet foods and drinks that are reported to be healthier than foods sweetened with real sugar. 

Are artificial sweeteners as healthy as food advertisers want us to believe?


Unfortunately, data suggests that artificial sweeteners are just as harmful as real sugar. Studies suggest artificial sweeteners, even at dosages considered safe by the FDA, can be toxic to the body and the brain, can lead to increased inflammation, and cause memory problems.

Moreover, artificial sweeteners do not make you thinner. Just like sugar, they increase your craving for sweet foods, thus increasing intake of unhealthy and empty calories.


Aspartame is one of the most commonly used artificial sweeteners.  It is commonly found in diet foods and drinks, such as diet soda, sugar-free gum, many sugar-free foods, and even prescription drugs and chewable vitamins. 

Aspartame effects on the brain:

Aspartame is associated with systemic inflammation, memory problems, migraine headaches, dementia, fibromyalgia, and even depression.

After aspartame is ingested, it is metabolized into 3 isolates:

  1. Phenylalanine (50%)

  2. Aspartic Acid (40%)

  3. Methanol (10%)


  • Phenylalanine can cross the blood brain barrier (a special protective layer in the blood vessels surrounding the brain - the blood brain barrier provides extra protection for the highly sensitive brain). Phenylalanine crosses the blood brain barrier and causes severe changes in the production of dopamine and serotonin, important neurotransmitters that play a role in mood, sleep, and digestion 1.

  • Aspartic acid can also cross the blood brain barrier and bind to a special receptor in the brain called the NMDA receptor. Excess binding to the NMDA receptor can lead to over-excitation of neurons, causing excitotoxicity. Excitotoxicity leads to neuron death. Excess damage to neurons leads to cognitive and memory impairment 2.

  • Methanol is a toxic substance metabolized in the liver into formaldehyde (the chemical used to preserve dead bodies for autopsy). Formaldehyde is metabolized into formic acid which in excess can cause metabolic acidosis and tissue injury 2. The eyes are particularly sensitive to the toxic effects of methanol, as methanol toxicity can lead to blindness1.

Aspartame’s metabolites are also found in natural foods (i.e., milk, tomato juice, fruits). However, when found in natural foods, they are bound to other proteins and thus are released more slowly into the blood. When aspartame is consumed, it is rapidly absorbed into the blood stream. Therefore these toxic metabolites accumulate more rapidly in the blood. This rapid accumulation increases the risk for toxicity.

Even at dosages considered safe by the FDA (≤ 40mg/kg), aspartame consumption has been shown to be toxic to the brain 2. Its metabolites cause an increase in pro-inflammatory molecules in the brain. These pro-inflammatory molecules increase inflammation in the brain and also break down the protective blood brain barrier. Aspartame impairs learning and memory even at dosages considered safe in humans 2.

A 2017 review of all the human and animal data on aspartame concluded that aspartame, even at recommended safe dosages might not be safe.  The data reviewed suggested not only that aspartame is neurotoxic, but that aspartame also causes widespread damage to other organs in the body by causing anti-oxidant/oxidant imbalance, inducing oxidative stress (which is a hallmark of systemic inflammation), and causing tissue and organ injury. Ingestion of aspartame therefore likely contributes to systemic inflammation in people with diabetes and obesity, who already have high levels of systemic inflammation, and likely worsens overall health of people with these diseases.

Aspartame may not only worsen existing inflammation in diabetics and obese people, but also can induce systemic inflammation in healthy individuals. This brings about the hypothesis of whether aspartame is associated with the increasing rates of autoimmune disorders in developed nations (where consumption of ‘diet’ foods is high).


Sucralose, also known as Splenda, is another artificial sweetener commonly used in diet foods and drinks. It was only introduced in 1999, and so there is less overall data about its effects compared to aspartame. There is not much data on humans, however rat studies show that sucralose can cause brain damage, especially to the the hippocampus (a region in the brain important for memory formation) 3. Sucralose also can decrease levels of good bacteria in the gut (good bacteria is important for proper gut health, immune system functioning, and is important for neurological and psychological health) 4. Moreover, when sucralose is cooked at high temperatures, it breaks down and interacts with other ingredients, which can be harmful. For example, sucralose can interact with glycerol which creates  chloropropanol, a chemical that may increase cancer risk 5.

How can you Avoid Artificial Sweeteners?

Now that you have been empowered with the knowledge about the harmful effects of artificial sweeteners, you are better equipped to make informed decisions about the substances you place in your body and that of your children’s.

What can you do to avoid intake of toxic Artificial sweeteners?

1. Limit your intake of sweet food and drinks.

Data suggests that both sugar and artificial sweeteners can increase systemic and brain inflammation. Sugar and artificial sweeteners also impair appetite mechanisms in the body (they can increase cravings for sweet foods) and thus cause weight gain.

The best way to avoid the harmful effects of artificial sweeteners and real sugar is to limit intake of sweet foods altogether.


2. Natural sugar substitutes

If it is difficult avoid sugars altogether, you can resort to natural sugar substitutes like monk fruit, stevia, xylitol. However, after my literature search of these three substances, I found a few limited animal studies that show that stevia can cause unfavorable changes in dopamine and serotonin secretion in rat brains6.


Whenever I have a sweet tooth, I prefer to either eat a piece of fruit (has a lower glycemic index than any processed sweet food) or chew a sugar free gum that contains xylitol, such as Pür gum.


3. Read food labels carefully

Foods that you never think would contain artificial sweeteners can contain aspartame or sucralose. Examples include diet/low sugar yogurt, salad dressing, whole wheat bread, condiments(i.e., ketchup), and sugar-free gum.

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