How safe is Aspartame?

DNA mutations, brain tumors, cancer, headaches and chronic fatigue – these are some of the side effects alleged to be associated with aspartame consumption.

I’ll admit I was concerned when I first heard these accusations. If you’re anything like me, an array of artificially sweetened foods such as nonfat yogurt, protein shakes, meal replacement bars and diet sodas have become a large part of your health conscious diet. If there were any truth to these claims I’d want to know about it. I figured other people would too, so I decided to roll up my academic sleeves, sweep aside the tabloid swill and dig into the real science on aspartame to get the straight facts.

Aspartame is simply two amino acids (L-phenylalanine and L-aspartic acid) linked together. About 30 years ago food chemists discovered when these two amino acids are joined together they provide a very sweet taste (180-200 times sweeter than sugar). Therefore, much less aspartame is required to obtain the same sweetness of sugar and the caloric yield is negligible.

Phenylketonurics – the truth!

Phenylketonurics: Contains Phenylalanine. What about that notorious health disclaimer on aspartame containing foods? Let’s look carefully at the facts.

Phenylketonuria (PKU) is an extremely rare condition that mainstream media incorrectly linked to aspartame. PKU is a central nervous system disease characterized by an inability to metabolize excess amounts of phenylalanine. L-phenylalanine is an essential amino acid. It is found in much higher doses in protein rich foods (such as meat, eggs and milk) than aspartame-containing products[1].

Dietary surveys of people in United States, Canada, Germany, and Finland show those considered to be on a “very high aspartame intake” still only consume approximately one-tenth of the daily intake recommended by the US Food and Drug Administration of 50 milligrams/kilogram/day[1]. Ingestion of aspartame does not cause PKU, and even PKU sufferers are unlikely to be harmed by the minimal amount of phenylalanine in aspartame.

Twenty-one years ago, one study on mice concluded that prolonged dietary ingestion of aspartame at levels 550 times the normal human daily ingestion was necessary to elicit a central nervous system deficit[2]. There have in fact, been over 200 studies conducted over the last two decades that support the safety of aspartame consumption. Trust the media not to let the facts get in the way of selling a story.

There is also the completely unfounded concern about the toxicity of aspartame. One recent study showed aspartame and another artificial sweetener combined couldn’t produce genotoxiciy (damage to DNA) at doses of 350 milligrams/kilogram/day![3] Aspartame’s two amino acids, L-phenylalanine and L-aspartic acid, are metabolized like all other amino acids[4].

Now, there’s a crusade against aspartame because of its conversion to formaldehyde. Well, I can end that campaign right now. The methyl group from aspartame is metabolized to methanol (an alcohol), then oxidized into formaldehyde, which is further oxidized into carbon dioxide. This fearful metabolic process is as common in our biology as talk shows in America. Ounce for ounce, tomato juice yields six times the methanol formation of a can of diet soda[5].

Over 100 countries including the US (and even the anally-retentive Australian TGA) have approved aspartame’s use. Aspartame is also approved by the World Health Organization. The US FDA commissioner even noted at the time of aspartame’s approval that few compounds have withstood such detailed testing and close scrutiny.

The unfortunate aspect is, public perception about aspartame has become so distorted and widespread that always eager-to-please food manufacturers have found it easier to rid aspartame from their formulations than quote the research. Next time someone forces their misinformed opinion of aspartame on you, just smile. Now you’ve got the facts, and you know better.


1. Butchko HH; Kotsonis FN. Acceptable daily intake vs actual intake: the aspartame example. J Am Coll Nutr. Jun;10(3):258-66,1991.

2. Potts WJ; Bloss JL; Nutting EF. Biological properties of aspartame. I. Evaluation of central nervous system effects. J Environ Pathol Toxicol. Jun-Jul;3(5-6):341-53, 1980.

3. Mukhopadhyay M; Mukherjee A; Chakrabarti J. In vivo cytogenetic studies on blends of aspartame and acesulfame-K. Food Chem Toxicol. Jan;38(1):75-7,2000.

4. Lehninger, Nelson, Cox. Principles of Biochemistry 2nd Ed. Worth Publishers 1997. p-527-529.

5. Butchko HH. Safety of aspartame. Lancet Apr 12;349(9058):1105, 1997.

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