Science Questions

What is Aspartame?

Sun, 7th Feb 2010

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John, Werrington asked:

What is aspartame and what does it turn into when it gets into the body?


Well aspartame, the sweetener, works because itís about 200 times sweeter as a molecule than sugar is.  But because it contains virtually no calories compared with a large number of calories from sugar, you can use it to replace the sweetening things in food that would normally be sugar, and therefore, cut the number of calories in food.  So thatís how it can be used to help people lose weight. 

The worry is, whether or not it gets metabolised or broken down in the body into something toxic.  So if you look at the molecular structure of aspartame, it consists of two amino acids.  One of which is called phenylalanine Ė perfectly healthy there, no problem with that.  Another one called aspartic acid Ė again, very common, no problem there.  The two are linked together though with a bridge molecule which is a methyl group, a carbon atom attached to a couple of hydrogens.  But when this molecule goes into your digestive tract, the acid and other chemicals in that environment actually break apart the two amino acids, the phenylalanine and the aspartate, and they get absorbed and used in the body in the same way any other amino acid would.  But the methyl group actually gets turned into a methanol, and the other name for methanol is wood alcohol. 

We know that methanol can be harmful to health when it goes into your body Ė although in itself, methanol is not harmful, it goes to the liver. There, enzymes break down alcohol, ethanol, ultimately into ethanoic acid, vinegar, and itís just excreted.  These enzymes also turn methanol initially into formalin, which is formaldehyde - a fixative - the same stuff you use to embalm bodies.  Ultimately, the formalin gets oxidized to make formate or formic acid.  This is the same stuff that ants squirt out their back end, which makes you sting.  Thatís not good because itís very toxic to mitochondria, the powerhouses in our cells.  Mitochondria supply energy to cells and if nerve cells don't have enough energy, they can die.

So if you have an intense ingestion of methanol, then the methanol can turn into formalin and fix your body internally, and also into formic acid which will deactivate your mitochondria, and that means nerve cells can die because they don't have enough energy.

The amount of methanol you get from aspartame is very, very low - a daily intake of probably less than a few milligrams or possibly 10 milligrams of methanol.  So probably trivial, probably not going to harm you, but the jury is out.  We just don't know, is really the answer.


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Trivial indeed, less than the amount you would get from a piece of fruit.

I disagree that the jury is out:

Unwarranted controversy over something can give off a false impression that both sides of the argument have merit, but this doesn't seem to be the case.

There is only one known health risk with Aspartame, and that is to people who cannot metabolize phenylalanine (a rare condition called phenylketonuria). But phenylalanine is an amino acid that's found in a million things, so aspartame is just one more to the list that people with this condition have to avoid. Madidus_Scientia, Tue, 9th Feb 2010

Good call. Thanks for your critical approach.

Chris chris, Tue, 9th Feb 2010 is really bad dont listen to any one that says it is not bad david, Mon, 5th Mar 2012 daivid, Mon, 5th Mar 2012

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