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Aspartame has long been the subject of controversy. Is there any truth to claims that the artificial sweetener can cause problems of the central nervous system, such as multiple sclerosis, or trigger other ill effects?


For many people, information about the human diet may seem like a revolving door. We are constantly hearing contradictory information about which types of foods or additives are good or bad.

This is the case with the artificial sweetener known as aspartame. Since artificial sweeteners have become a mainstay in our diet there has been controversy over its safety.

Artificial sweeteners give foods and beverages the taste of sugar without the calories. This is considered to be beneficial, especially in light of the obesity epidemic. But even in the case for weight reduction, it's not certain that these products really achieve long-lasting weight loss. In fact, there are arguments that intense sweeteners can actually increase one's appetite for sweet foods, promote overeating, and may even lead to weight gain. And over the years scientists have felt compelled to look at the relationships between sweeteners and a variety of illnesses.

Two recent reviews of scientific literature on aspartame have endorsed its safety.

One published in the journal Critical Reviews in Toxicology in 2007 and led by Bernadene Magnuson, who has ties to the artificial sweetener industry, concluded that there was no link between illnesses of the central nervous system and aspartame. (Dr. Magnuson was at the University of Maryland when the study was published.)

Similarly, Harriett Butchko and colleagues at NutraSweet Co., reported in the journal Regulatory Toxicology and Pharmacology that there is no concrete evidence that aspartame affects brain function or behaviour, or causes any form of brain damage.

Both reviews also concluded there was no evidence to support an association between aspartame and cancer.

On the other hand, Petro Humphries, a researcher at the University of Pretoria in South Africa who reported no links with the artificial sweetener industry, led another review of the literature that found that consumption of aspartame could cause neurological and behavioural disturbances in sensitive individuals.

These included headaches, insomnia and seizures, and could in part be attributed to changes in regional brain concentrations of certain neurotransmitters, or chemical messengers, according to the findings published in the Journal of Clinical Nutrition in 2008.

Dr. Humphries and colleagues concluded that excessive aspartame ingestion could, in sensitive individuals, be involved in cell and tissue changes that lead to certain mental disorders and also compromise learning and emotional function. They suggested that serious further testing and research be undertaken to eliminate the controversy over this product.

Even without further study, there are already recommended limits on how much aspartame a person should ingest each day.

The U.S. Food and Drug Administration has established acceptable daily intake of 50 milligrams per kilogram of body weight per day. The European Food Safety Authority has set daily intake levels of 40 milligrams per kilogram of body weight.

Given this information, it is important for people to remember that our consumption of foods and beverages that contain artificial sweeteners should always be guided by moderation.

Dr. Peter Carlen is a neurologist at the Krembil Neuroscience Centre, University Health Network in Toronto and head of the Division of Fundamental Neurobiology of the Toronto Western Research Institute.