I've written an article about the artificial sweetener aspartame a couple of years ago published in the Australian Fit Lifestyle magazine. In the article I listed a number of scientific studies that showed the possible harmful effects of the long-term use of aspartame and encouraged the readers to reduce or avoid aspartame consumption until the results of a safety re-evaluation conducted by the European Food Safety Authority (EFSA) are released. Well, three years after the EFSA launched a public call for the submission of studies concerning the use aspartame, the European organization finally released their findings in December 2013 and the verdict about aspartame remains unchanged. The EFSA recommends that the current acceptable daily intake level for aspartame at 40mg per kg of body weight per day is safe and does not cause neurological damage, pregnancy issues and cancers in healthy people. However, the acceptable daily intake level is not applicable for people who have phenylketonuria, a genetic disorder that causes the accumulation of phenylalanine in the body, one of the metabolites of aspartame, which can lead to a number of serious medical problems.
Being an avid Coke Zero drinker, I welcomed the newest evaluation that deemed aspartame consumption safe. While there's no reason to question the the experts' ability to review literatures available to them and to process the scientific data in an unbiased fashion, it does make me wonder why only a few of the studies reviewed suggested the potential harmful effects of aspartame, with almost all of which were discounted for being scientifically insignificant.
A quick search in www.pubmed.org (US National Library of Medicine, National Institute of Health) indicated that 9 papers were published and indexed in 2014 with a key word "Aspartame" at the time this article was written. Three of the articles were about the formulation of compounds/goods, one was about sewage contamination and one investigated the use of fructose instead of aspartame in very low calorie diet for obese people and found that the subjects lost an average of 8.2kg after 4 weeks of eating fructose (Noren and Forssell 2014, Nutrition Journal). The rest of the 4 studies focused on the physiological and biochemical effects of aspartame in animals: Kim et al (2014, Cardiovascular Toxicology) showed that high-dosage treatment of aspartame can negatively affect the antioxidant and anti-atherogenic activity of high-density lipoprotein (HDL) in Zebra fish; Nosti-Palacios et al (2014, International Journal of Toxicology) found that the administration of aspartame and insulin may induce toxicity in the brain and liver in diabetic rats; Ashok and Sheeladevi (2014, Redox Biology) suggested that long term aspartame exposure can alter the antioxidant status of the brain and could induce apoptotic (programmed cell death) changes in rat brains; Finamor et al (2014, Neurochemical Research) stated that the chronic exposure of the human acceptable daily intake level for aspartame at 40mg per kg of body weight in rats can cause oxidative damage in the animals tested.
I stand to be corrected but based on my brief and limited literature research, almost all relevant studies published in the first 9 months of 2014 depicted a grim picture on the long term use of aspartame in animals. The published summary of the EFSA findings on the other hand, only mentioned a few studies stating the negative effect of aspartame while the majority of the studies received and reviewed by EFSA for this re-evaluation seemed to suggest that aspartame use has no measurable effect on humans and animals. I have no doubt that 40mg per kg of body weight per day of aspartame is generally safe for human consumption, because otherwise we would all have brain damage by now. However, the real long-term effect of aspartame consumption in humans has not yet been established. Moreover, the food and beverages containing aspartame are generally not very healthy. So my advice to you about aspartame use remains the same: reduce your intake, and avoid if possible.