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Aspartame and your Brain

You’ve probably heard of aspartame, the artificial sweetener known to be carginogenic (cancer-causing). It is also known as additive 951, aspartame is 200 times sweeter than sucrose (white sugar).

Aspartame is in way more things that we consume than you are lead to believe. All those diet and sugar-free drinks and foods, chewing gums, gummy vitamins, and some medications. It’s hardly ever listed as aspartame and is more commonly listed as additive 951.

Aspartame is still widely marketed and used as a sugar-free option, but I’m here to explain why you need to love your brain and nervous system instead.

Just a few of the adverse effects of aspartame consumption include cognitive and memory impairments, headaches, migraines, irritable moods, anxiety, depression, and insomnia. I’m going to explain why these can happen, and how aspartame can directly affect your brain chemistry and functioning.

Aspartame and brain neurochemicals

When you consume aspartame it is then broken down into phenylalanine, aspartic acid, and methanol.

If you look on a Coke No Sugar bottle you will see that it says ‘contains PHENYLALANINE’ which is due to the breakdown of aspartame.

~ put your science hat on ~

Phenylalanine and aspartic acid can cross the blood-brain-barrier (BBB) and cause a whole range of problems here. For something to cross the BBB it needs a transport channel to pass through. Phenylalanine uses the same channel as tryptophan and tyrosine which are needed to make serotonin and dopamine. Excess phenylalanine from aspartame competes with tryptophan and tyrosine to get into the brain and can cause reduced production of neurotransmitters like serotonin, dopamine, and norepinephrine.

Aspartic acid is converted into glutamate which causes hyper-excitability, free radical release, oxidative stress, and degeneration of nerve cells. This can causes issues such as cognitive impairments, headache, migraines, vision problems, tinnitus, irritable moods, anxiety, depression, and insomnia.

Aspartame and Cognitive Impairment

Some common cognitive symptoms associated with aspartame consumption include reduced attention span, poor information processing, slower processing speed, and long-term memory loss.

A lot of this is due to the excess phenylalanine crossing into the brain and adversely affecting brain functioning.

Aspartame and Mood

Behavioral changes in the human mind can be altered by aspartame due to the increased amount of phenylalanine and its effect on brain neurotransmitter function. Serotonin plays a major role in the processing of emotional information and our moods. Abnormalities in the serotonin pathway can predispose people to low mood and depression.

Negative mood and depression episodes in healthy university students were more frequent after a high aspartame consumption, compared to a low aspartame consumption. Individuals with pre-existing mood disorders were particularly sensitive to aspartame.

Aspartame and Migraines

Several studies have shown that aspartame has the potential to trigger headaches and migraine.

A double-blind, placebo-controlled study of more than 200 adults with migraines found that aspartame users experience significantly more headaches/migraines over 14-24 days.

This may be due to the increased oxidative stress on the brain, increased inflammation, neurotoxicity, or reduced serotonin levels.

Aspartame may be considered neurotoxic because of its breakdown into methanol, formaldehyde, and formate which are all known neurotoxins.

High aspartic acid levels after aspartame consumption can also cause trigger headaches due to overstimulation of some nerve cells in the brain and upper spinal cord.

Aspartame and Sleep

Aspartame may cause sleep disturbances due to changes in cortisol (our main stress hormone), reduced serotonin, or loss of vagal nerve balance.

Rat studies have shown that aspartame significantly elevates cortisol levels. No human studies have shown this so far but we know that high cortisol levels contribute to sleep issues.

Serotonin is a precursor to our wonderful sleep neurotransmitter, melatonin. Low serotonin levels= lowered melatonin levels.

Are you ready to ditch the artificial sweeteners yet?

Remember that aspartame can be hidden as additive 951, check your labels and opt for the full fat, non-diet versions always!


Arbind Kumar Choudhary & Yeong Yeh Lee (2017): Neurophysiological symptoms and aspartame: What is the connection?, Nutritional Neuroscience, DOI: 10.1080/1028415X.2017.1288340

Humphries P, Pretorius E, Naude H. Direct and indirect cellular effects of aspartame on the brain. Eur J Clin Nutr. 2008;62 (4):451–62.

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