Late last month, Pepsi announced that it will remove the artificial sweetener aspartame from its diet Pepsi products by the end of this year, bowing to consumer concerns that the sweetener poses a number of health risks. Questionable Internet sources have stoked these fears, accusing aspartame of causing cancer, multiple sclerosis, blindness, seizures, memory loss, depression, and birth defects. One of those dubious sources, alternative medicine guru Dr. Joseph Mercola, even called the sweetener "By far the most dangerous substance added to most foods today."

It is no wonder, then, that some individuals worry that they may be "sensitive" to aspartame, and report experiencing symptoms like headache, nausea, dizziness, and congestion after consuming food containing the sweetener. A study published in March to the journal PLoS ONE put their claims to the test, however, and found no evidence of any acute adverse response to aspartame.

48 self-reported aspartame sensitive individuals took part in the study, which was conducted primarily by researchers at Imperial College London. These individuals, who were actively avoiding aspartame in their diets on account of their symptoms, were then matched by gender and age to 48 non-sensitive individuals.

Subjects in both groups were given a cereal bar laced with 100mg of aspartame -- roughly the same amount in a can of diet soda -- or a normal bar. Subjects provided blood samples before the test and four hours later, as well as urine samples at three different times over the following 24 hours. All symptoms were assessed and monitored for four hours after eating. A week later, the process was repeated so that subjects could eat both bars. The study was double blind, so neither the experimenters nor the subjects knew what bars they were receiving.

Analyzing the results, the researchers found that "none of the rated symptoms differed between aspartame and control bars, or between sensitive and control participants." Moreover, all subjects' blood work remained normal, as did every biomarker in the urine analysis.

The blood work and urine analysis were particularly telling. Aspartame opponents correctly point out that the chemical breaks down into phenylalanine, methanol, and aspartic acid, three chemicals that they insist are extremely toxic. These chemicals can indeed be dangerous, but only in high amounts. Turns out, the concentration of phenylalanine actually decreased in subjects' blood. Methanol and aspartic acid levels were so minute that neither of the chemicals were even detected. The researchers also noted that methanol is produced in higher concentrations in the body after drinking fruit juice.

"This independent study gives reassurance to both regulatory bodies and the public that acute ingestion of aspartame does not have any detectable psychological or metabolic effects in humans," the researchers conclude.

It should be noted that study was conducted over a short timespan, and thus can't rule out the possibility of adverse health effects resulting from long-term consumption of aspartame. However, a considerable number of studies dating back 30 years have already looked at this and concluded that the sweetener is completely safe.

Source: Sathyapalan T, Thatcher NJ, Hammersley R, Rigby AS, Pechlivanis A, Gooderham NJ, et al. (2015) Aspartame Sensitivity? A Double Blind Randomised Crossover Study. PLoS ONE 10(3): e0116212. doi:10.1371/journal.pone.0116212