Aspartame and Phenylalanine
Another worry is whether loading our blood with higher concentrations of phenylalanine (or its metabolite, tyrosine) is good thing. People who don’t believe there is any danger argue that we get significantly more phenylalanine from most of the foods we eat, so it shouldn’t be a problem in the low doses which come from aspartame. The issue with that argument is that we also get a significant amount of other amino acids as well.
When our blood is loaded with only phenylalanine, and to a lesser extent tyrosine, it is documented to cause depletion of essential amino acids in our brain. For people suffering from phenylketonuria, this issue is of the utmost seriousness as their body cannot effectively metabolise the phenylalanine, causing it to accumulate and be converted to phenylpyruvate. The disease has serious repercussions, especially on brain development, if not treated and controlled through low dietary intake of phenylalanine.
Phenylketonuria is rare, and most people will probably not intake enough phenylalanine from aspartame to load their blood, especially since most people will metabolise it to tyrosine which is much less harmful. Nonetheless, for habitual users the risk is greater than for those who only consume Nutrasweet, Equal, or other aspartame-containing products every now and then.
Bottom line, aspartame carries a risk. As with sucralose, there is evidence that in at least a small amount of people, side-effects such as headaches and gastric upset could occur. There is also the risk that it could contribute to carcinogenic formaldehyde-DNA adduct formation. Definitely do not give aspartame-containing products to children, as it requires far less aspartame to be considered a high dose, and the risk is far greater with phenylalanine in the developing brain.
Saccharin: Potentially Safe
Saccharin, despite once being required to carry cancer warnings on the label, was in 2000 decided not to be carcinogenic in humans. The resolution came about via a discovered difference in the way male rats process saccharin in their bladder, the rats having certain factors present which humans do not have. Thus, the warning was removed.
Saccharin has an over one hundred year history, and of all the artificial sweeteners seems to, at this point, carry the least risk. It is not metabolised by the body, accumulates to a far lesser extent than sucralose, and seems to accumulate primarily in the bladder, where it is far less likely to cause harm and far more likely to be excreted than in the liver or kidneys. Saccharin has not been found to bind to the DNA, as aspartame can, and the toxicity which has been reported in high amounts seems to be related to its sodium component, not the saccharin part. Sodium is consumed in much higher amounts regularly in the form of table salt, and saccharin is not a significant source of sodium.
For reasons associated with all artificial sweeteners, the use of saccharin is not a suggested method for calorie reduction. These reasons are extensively discussed below.
Acesulfame-K: The Great Unknown
Acesulfame potassium was discovered in 1967, but has only been approved for use in the US in soft drinks since 1998. There is not a lot of literature attesting to its toxicity, but that is precisely the problem: there is simply not a lot of literature on this substance. This is stated in an article from 2006, where the author points out that the research the FDA based its approval on was carried out by the scientist and company who marketed acesulfame-K, and that the research had a number of flaws.
It may turn out that there is no problem with acesulfame-K, but at this time there really is not enough research to determine whether or not it is safe. Acesulfame-K is relatively unused, and most often is used in conjunction with other artificial sweeteners in order to mask its bitter aftertaste, but it turns up in sports-oriented drinks, including protein powders, so be aware of your ingredients!