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Jonathan Houser

Date: 11/16/2005


Aspartame: A Brief Overview


If you have ever tried a diet soda then you have consumed aspartame, a chemical with quite a history. It is one of the most commonly used food additives in this country, and so it comes as no surprise that its use has been viewed with some concern. It has been estimated that well over 100 million Americans consume products containing aspartame every day. Numerous reports have come in from consumers linking aspartame to various problems from headaches to multiple sclerosis. There are numerous websites claiming that aspartame causes or inflames dozens of disorders. Of the many symptoms that have been linked to aspartame usage, I have selected only a handful to mention here. A thorough report on aspartame could (and does) fill volumes with relevant data. The producers of aspartame claim that their product is virtually harmless, and the link to aspartame’s official website is , but can they really be trusted? On this website I attempt to approach the subject of this small, two amino-acid peptide in an objective manner by providing some of the scientific data regarding this familiar food additive.


The History

            Aspartame has been studied by the FDA since the sixties; well before it was approved for use by the public. L-aspartyl-L-phentlalanine methyl ester (aspartame) was discovered completely on accident in  late 1965. Chemists were working on producing an inhibitor for the gastrointestinal hormone gastrin, and had accidentally spilled some of the intermediate chemicals on their hands. Later one of the chemists licked his finger to lift a paper when he “noticed a very strong, sweet taste (Stegink, Filer, 1984).” The chemists working in the Searle laboratories had stumbled onto something that would spur decades of controversy and countless hours of investigative research.


The Controversy

            Any product that is approved for use by the general public can and should be subject to investigation so that any and all reported side-effects can be examined. This is why all products that are approved for use by the FDA undergo extensive premarket evaluations. Those products that demonstrate significant side-effects must have warning labels for any possible harmful effects from consuming it. Aspartame in particular has been labeled by many as a “poison.” One need not look further than to type in “aspartame” on the world wide web and one will find dozens of websites filled with testimonials from individuals who claim that their lives have been ruined by the artificial sweetener. One such site is which has links to sites that refer to those who distribute aspartame as “terrorists” for with-holding critical health information on aspartame.

            Once a product has been approved for use by the public, it is the job of the FDA’s ARMS or “Adverse Reaction Monitoring System” to remain vigilant to any possible side-effects of these products. The ARMS has worked with the CDC for decades to gather a database of information on the numerous reported complaints from individuals who have used aspartame. After a report broadcasted by CBS in 1984 on the allegations against aspartame, the number of complaints sky-rocketed. It was clear that more research was required. There has been an enormous amount of scientific inquiry into aspartame, and only a very small fraction of this research is referred to on this site. A great deal of this research is available in the various legitimate scientific journals published in America. Many of the dozens of symptoms and illness reportedly caused by aspartame consumption have been addressed in this research, and many of the claims against aspartame have been rejected as coincidental or untrue. Through the years the number of complaints has leveled off to about 300 per year. Aspartame is probably the most intensively studied food additive in history. Because it is still considered safe by the FDA, it remains on the market in the United States and is consumed by millions every day.


The Symptoms



            Possibly the most common symptom affecting the American population, headaches, in one form or another, affect millions of Americans every year. Many reported complaints from aspartame users involve headaches. In response to this, many experiments have been performed to ascertain the possible link between the artificial sweetener and headaches. Some of these experiments include the double-blind pre-market experiments from the 1970’s, along with clinical studies conducted by the FDA in response to consumer complaints.

            One of the most thorough experiments was performed by Schiffman, Buckley, and colleges published in the 1987 N. England Journal of Medicine. In this experiment they used 40 participants who had reported complaints to the FDA about headaches within 24 hours of consuming aspartame. These participants were studied at Duke University Medical Center in North Carolina for 6 days. This allowed for detailed monitoring of their status as well as controlling for variation in diet and activity. Each participant was given a physical examination and their blood chemistry was also thoroughly examined before the experiment began. The experiment was randomized and double-blinded to prevent possible prejudice from the experimenters. A major critique of this experiment is that it failed to take into account the possibility of long-term exposure to aspartame. This critique was addressed by the experimenters by explaining that, since consumers associated symptoms with aspartame based on short term usage, then the 24 hours following aspartame intake would be the most important time period to examine experimentally. The long-term effects of aspartame usage were examined in a 6-month experiment similar to the above mentioned experiment, and outside the hospital setting (Leon  at el. 1989). This long-term experiment exposed the participants to dosages of aspartame that were well above the amounts that average Americans would consume. This dosages were referred to as “abuse dosages” and they did not have any significant harmful effects on the participants. The results of these experiments show that aspartame IS NOT associated with as increase in headaches.



            Experiments have shown that very high concentrations of the naturally occurring amino-acid Aspartate acts as a neurotoxin in some lab animals. It was shown that large intakes of aspartame can increase the blood levels of aspartate, but it was well within normal concentrations and well below harmful concentrations(Stegnik,Filer,Baker 1981). Additionally, this increase in concentration  required the equivalent of drinking 24 liters of aspartame-sweetened beverage at a single sitting. Further experiments were done where participants were administered aspartame at either 100, 150, or 200 mg/kg body weight illustrate that blood-aspartate levels do not increase in a “dose-dependent fashion” and this “indicated that the rate of its (aspartate’s) metabolism was greater than that of its absorption” (Tschanz, Butchko, Stargel, Kotsonis, 1996).  Both experiments agree that aspartame does not cause harmful effects in humans, but their conclusions seem somewhat in contest with each other.



            Aspartame is a polypeptide and is therefore broken down into amino acids in the small intestine. Phenylalanine is a component of Aspartate and therefore individuals with PKU, an inherited disorder which can lead to permanent mental retardation,  SHOULD NOT consume products containing aspartame. This is why products containing aspartame are required by the FDA to have the warning label “Phenylketonurics: CONTAINS PHENYLALANINE.” For individuals without PKU, phenylalanine can be safely digested and hence, aspartame poses no health risk in this respect.



            Methanol, or wood alcohol, can be very dangerous and is capable of causing permanent loss of vision if consumed. Experiments have shown that methanol damages the human body through the buildup of formate, not formaldehyde as some claim (Tephly,1991). Since aspartame is broken down into methanol in the intestine, this led some to claim that aspartame leads to methanol-poisoning. Further experiments dealing with aspartame’s digestion have indicated that even high rates of aspartame consumption do not lead to increases in the levels of formate in the blood. These experiments show that formate is excreted into the kidneys as quickly as it is formed, as measured by the concentration of formate in urine from 0 to 4 hours after “aspartame loading” and from 4 to 8 hours after loading. These findings indicate that aspartame does not cause methanol poisoning (Stegink et al., 1981).


Allergic reactions

            Proteins are an important part of the normal human diet. Aspartame is a simple protein consisting of two amino acids; aspartic acid (aspartate) and phenylalanine. It is easily digested by enzymes known as esterases and peptidases in the gut. These enzymes allow us to breakdown proteins into smaller components that are then absorbed into the blood. Experiments using radio-labeled amino acids have been conducted to examine the process of aspartame digestion in humans. The results of this study show that aspartame was digested easily by peptidases and no aspartame was detected intact in the bloodstream(Tobey, Heizer 1986). Also, evaluations from the CDC illustrate that aspartame does not induce allergic reactions, however the CDC admits the extraordinary difficulty in obtaining participants suitable for study. In one study, 3 documented cases of allergy to aspartame occurred, but these results failed to be reproduced in double-blinded follow-ups. Further experiments show that aspartame is no more likely to cause an allergic reaction than a placebo (Geha et al. 1993).



            Some studies have indicated that Aspartate intake can actually induce hunger in humans(Blundell, Hill 1986). Another experiment by Bala and Hagan demonstrated that masking the sweet taste of aspartame results in no increase in hunger when administered the artificial sweetener(Brala, Hagan, 1983). Numerous other studies abound testing the hypothesis that aspartame causes or increases hunger in various age groups of children and adults. In these experiments drinks were administered that were flavored by aspartame, sucrose, saccharin, as well as mineral water. These experiments all failed to reproduce the effect that aspartame increases the perceived hunger of the participants (Tschanz,1996).




Brala, P. and Hagan, R. L. (1983), Effects of sweetness perception and caloric value of a preload on short term intake, Physiol. Behav., 30, 1.


Blundell, J. E. and Hill (1986), A. J., Paradoxical effects of an intense sweetener (aspartame) on appetite, Lancet, 1, 1092.


Geha, R., Buckley, C. E., Greenberger, P., Patterson, R., Polmar, S., Saxon, A., Rohr, A., Yang, W., and Drouin, M. (1993), Aspartame is no more likely than placebo to cause urticaria/angioedema: results of a multicenter, randomized, double-blind, placebo-controlled, crossover study, J. Allergy Clin. Immunol., 92, 513.


Leon, A. S., Hunninghake, D. B., Bell, C., Rassin, D. K., and Tephyly (1989), T.R., Safety of long-term large doses of aspartame, Arch. Intern. Med., 149, 2318.


Stegink, L. D., Brummel, M. C., McMartin, G., Martin-Amat, Filer, L. J., Jr., Baker, G. L., and Tephly, T. R. (1981), Blood methanol concentrations in normal adult subjects administered abuse doses of aspartame, J. Toxicol. Environ. Health, 7, 281.


Stegink, Lewis D., Filer, L. J. Jr. (1984), Aspartame Physiology and Biochemistry, Copyright By Marcel Dekker, Inc.


Stegink, L. D., Filer, L. J., Jr., and Baker, G. L. (1981), Plasma and erythrocyte concentrations of free amino acids in adult humans administered abuse doses of aspartame, J. Toxicol. Environ. Health, 7, 291.


Tephly, T. R. (1991), The toxicology of methanol, Life Sci., 48, 1031.


Tobey, N. A. and Heizer, W. D. (1986), Intestinal hydrolysis of aspartylphenylalanine – the metabolic product of aspartame, Gastroenterology, 91, 931.


Tschanz C., Butchko H. H., Stargel W. W., Kotsonis F. N. (1996), The Clinical Evaluation of a Food Additive, Assessment of Aspartame,  Copyright CRC Press, Inc.





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