New review proclaims aspartame to be safe, but is it?

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Aspartame is a commonly used artificial sweetener. It’s also, arguably, the most controversial foodstuff in the human diet. Originally passed as ‘fit to consume’ by the FDA in the USA in 1981, its history as a food ingredient has been the subject of scientific and political intrigue. The companies that make it and ‘expert panels’ conclude it is safe. Yet, anecdotal reports on the web and elsewhere about that claim aspartame has the capacity to damage human health and cause symptoms that range from headaches and seizures and multiple-sclerosis type symptoms and depression.

Recently, a group of scientists from the USA, UK and the Netherlands, apparently reviewed over 500 studies relating to the safety of aspartame, and concluded that there is no credible evidence that aspartame is unsafe. Though they did conclude that some people might be prone to headaches after consuming it.

This review, which basically gives aspartame a clean bill of health, was funded by the aspartame manufacturer Ajinomoto. But apparently, the committee that wrote the report did not know who the sponsor was until after they had completed their work.
So, apparently, a group of scientists are invited to write a scientific review, but had no idea who was behind it or where the money to conduct the review was coming from. Did none of the scientists think to ask? Did not even the chair of the committee know? This all seems very odd to me.

And the fact remains, the research reveals quite a body of evidence that links aspartame with adverse effects on health. To understand this, we need to know something of the basic biochemistry of aspartame: it is composed of two amino acids (phenylalanine and aspartic acid), as well as what is known as a methyl group. Once in the digestive tract, the body can digest aspartame down to its two amino acids, and the methyl groups ends up being spliced off to form something called methanol. This is crucially important as methanol (the prime constituent in methylated spirits) has toxic potential and may also be converted to formaldehyde (used for preserving dead bodies) within the body [2].

It has been demonstrated in animals that low level ingestion of aspartame can lead to formaldehyde accumulation in the various parts of the body including the liver and brain [3]. In addition, several human studies have found that chronic, low-level formaldehyde exposure has been linked with a variety of health issues including headaches [4-6], fatigue [4,5], chest tightness [6], nausea and lack of concentration [7], seizures and behavioural impairment [6]. Aspartame consumption in humans has been found to induce physiological changes that might increase the risk of seizure [10]. In addition, at least one study has linked aspartame use with depression in individuals susceptible to mood disorder [11]. Other studies have linked aspartame ingestion with headaches [12,13].

What is perhaps most concerning about the research on aspartame relates to the apparent relationship between a study’s source of funding and its findings. An on-line review of the evidence finds that while 100 per cent of industry-funded studies conclude aspartame is safe, 92 per cent of independently funded research and reports identified aspartame as a potential cause of harmful effects [14].

One reason for this disparity may relate to something known as ‘publication bias’. Basically, the industry may choose only to publish the results of studies it likes the look of. Another explanation relates to the fact that many industry-funded studies seem to have been designed in a way that would make it unlikely for any harmful effects of aspartame to be detected. For instance, industry-funded studies have often given aspartame in the short term, many of them for a single day only. These methods in no way replicate the long term, drip-feed type of consumption many people experience in real life.

While long-term studies of the effects of aspartame have not been done in humans, these have been done in animals. In a recent study, Italian researchers fed aspartame in a variety of doses to rats in the long term [15]. The rats were given aspartame in their food supply from the age of 8 weeks until they died. Rats consuming aspartame were found to be at significantly increased risk of several forms of cancer including lymphoma and leukaemia (cancer of the white blood cells).

An increased risk of these conditions was found even at levels of aspartame intake lower than the official upper limit for humans. While in Europe intakes of 40 mg of aspartame per Kg of body weight per day are considered safe, an increased risk in cancer was seen in rats consuming just half this amount. Notably, this study was dismissed by the committee responsible for the latest review because of “methodological and interpretation errors.” Which is a bit rich, bearing in mind the inadequate design of the studies so often used to vindicate aspartame.

I remain deeply suspicious of aspartame, and the politics that surround it. I have no resistance to admitting that, personally, I never knowingly consume this additive, and have not done so for the past 15 years.


1. Magnuson BA, et al. Aspartame: A Safety Evaluation Based on Current Use Levels, Regulations, and Toxicological and Epidemiological Studies
Critical Reviews in Toxicology 2007;37(8):629-727

2. Kavet R, et al. The Toxicity of Inhaled Methanol Vapors. Critical Reviews in Toxicology 1990 21;1:21-50

3. Trocho C, et al. Formaldehyde Derived From Dietary Aspartame Binds to Tissue Components in vivo. Life Sciences 1998 63;5:337

4. Main DM, et al. Health Effects of Low-Level Exposure to Formaldehyde. Journal of Occupational Medicine 1983 25;896-900

5. Olsen JH, et al. Formaldehyde induced symptoms in day care centers. American Industrial Hygeine Association Journal 43;5 366-370

6. Burdach S, et al. Damages to health in schools. Complaints caused by the use of formaldehyde-emitting materials in school buildings. Fortschritte Med 1980 98 11; 379-384

7. Main DM, et al. Health Effects of Low-Level Exposure to Formaldehyde. Journal of Occupational Medicine 1983 25;896-900

8. Burdach S, et al. Damages to health in schools. Complaints caused by the use of formaldehyde-emitting materials in school buildings. Fortschritte Med 1980 98 11; 379-384

9. Kilburn KH, et al. Neurobehavioral and respiratory symptoms of formaldehyde and xylene exposure in histology technicians. Arch Env Health 1985 40; 4; 229-233

10. Camfield, PR, et al., Aspartame exacerbates EEG spike-wave discharge in children with generalized absence epilepsy: a double-blind controlled study. Neurology, 1992;42:1000-1003

11. Walton RG, et al,. Adverse reactions to aspartame: double-blind challenge in patients from a vulnerable population. Biol Psychiatry. 1993;34(1-2):13-17

12. Van Den Eeden SK, et al. Aspartame Ingestion and Headaches: A Randomized, Crossover Trial. Neurology. 1994;44:1787-1793

13. Lipton RB, et al. Aspartame as a dietary trigger of headache. Headache. 1989;29(2):90-92


15. Soffritti M, et al. First experimental demonstration of the multipotential carcinogenic effects of aspartame administered in the feed to Sprague-Dawley rats. Environ Health Perspect. 2006 Mar;114(3):379-85]

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