Although the dangers of aspartame are well known to the public, the scientific community appears reluctant to research the biochemistry and neurophysiology of the sweetener. The reason for this is quite simple. The food industry is very powerful and rich and they do not appreciate their ‘foods’ being investigated over safety concerns. As a result the actual funding for research to investigate the numerous and growing cases of aspartame toxicity that are reported in the medical literature is small. However, that is not to say that research into the effects of aspartame on the brain have not been performed, as safety studies date back many decades (thanks to researchers such as Wurtman). The main concerns over the toxicity of aspartame centre on its ability to increase levels of formaldehyde in the body through the natural metabolism of the methanol component of the molecule, as well as its ability to alter the neurochemistry of the brain because of the way aspartame can affect amino acid uptake and metabolism in the central nervous system.
On this latter point, there appears to be an additional risk if the aspartame is consumed with glucose. This is concerning because increasingly aspartame is added to foods and drinks, not as an alternative to sugars, but in addition to them. For example, one study1 investigated the effects of aspartame at a dose of 200 mg per kg body weight alone and in addition to 3 grams per kg body weight of glucose. The aspartame administration was able to elevate brain levels of the amino acids tyrosine and phenylalanine, suggesting that brain chemistry had been altered. However, when aspartame was administered with glucose the rise in brain levels of phenylalanine doubled. The brain levels of both tyrosine and phenylalanine were correlated closely with the blood ratios of these amino acids, confirming that the brain changes were likely as a result of changes to plasma levels of amino acids caused by aspartame administration. Therefore in rats at least, aspartame can alter brain chemistry through modulation of amino acid ratios.
When the effects of glucose were analysed in isolation, the glucose administration caused increases in brain levels of a group of chemicals called the 5-hydroxyindoles which includes serotonin and 5-hydroxyindoleacetic acid. These changes occur because the glucose increases insulin release which pushes the branched chain amino acids (valine, leucine and isoleucine) into skeletal muscle cells. Because the branched chain amino acids normally competitively block the uptake of tryptophan into the brain, glucose plays a role in removing this inhibition and causing brain levels of tryptophan to rise. As tryptophan is the precursor to the 5-hydroxyindoles, glucose administration can raise brain levels of these compounds. However, aspartame was shown to block the serotonin increasing effects of glucose, causing reductions in the natural increase in serotonin following glucose administration. In addition, aspartame and glucose was able to lower brain levels of the branched chain amino acids to a greater extent than either compound in isolation.
Therefore it appears that aspartame is able to alter the chemistry of the brain by modifying ratios of amino acids. Because it is these amino acids that create the neurotransmitters required for movement, motivation, sleep, arousal and large list of other brain functions, it is clear that mechanisms exist to explain the strange neurological problems associated with aspartame consumption. Some people are particularly sensitive to aspartame, whereas others appear less so. This may relate to biochemical nuances created by genetic differences. However, this does not mean that aspartame is safe or should be consumed by those who do not experience adverse effects. The ability of glucose to enhance the brain changes caused by aspartame are particularly concerning given the increasingly common practice for aspartame to be added to drinks and foods alongside glucose and other sugars. The reason for the requirement to add aspartame in addition to sugars in many foods is not clear, however, it appears to be more to do with profit and health.
Dr Robert Barrington’s Nutritional Recommendation: Based on the findings of this and other studies, I recommend that those interested in maintaining their health avoid aspartame containing products.
RdB
