Updated on 5/9/2006.
As you may know, I'm not a fan of artificial sweeteners. I think it best to avoid both aspartame and saccharin. For now, I'm still keeping an eye on a newer one, sucralose (Splenda). A product of British research, sucralose is 600 times sweeter than sugar and maintains its sweetness under a wide range of temperatures, making it a useful option for cooking and baking. It tastes better than aspartame and saccharin and, so far, looks safe. (But so did saccharin and aspartame when they were introduced.)
Like most artificial sweeteners, aspartame has a peculiar taste. I have seen a number of patients - mostly women - who report headaches from using it, and some women also find that aspartame aggravates PMS. This compound is suspected of being an "excitotoxin," a compound that can damage nerve cells by overstimulating them. I would warn anyone with a neurological disease to avoid it. At the same time, I've seen no scientific support for assertions on the Internet that there is an "aspartame disease" or that it worsens symptoms of multiple sclerosis, lupus, and fibromyalgia. Indeed, the Multiple Sclerosis Foundation has published a letter on its Internet site refuting the notion that aspartame provokes or worsens MS.
We do know that people with the genetic disease phenylketonuria (PKU), those with advanced liver disease, and pregnant women with high levels of the amino acid phenylalanine in their blood have a problem with aspartame because they do not effectively metabolize phenylalanine, one of aspartame's components. High levels of phenylalanine in body fluids can cause brain damage. For this reason, the FDA requires that all products containing aspartame must include a warning to phenylketonurics that the sweetener contains phenylalanine.
For every one else, although available evidence suggests that occasional use of aspartame presents no great risk, I would however recommend following the precautionary principle. In other words, don't use it.
I think it's wise to consume moderate amounts of sugar rather than any artificial sweeteners. Sugar is safe when used in moderation, and relatively low in calories (about 15 per teaspoon).
Also, keep in mind that no evidence exists to suggest that using artificial sweeteners helps anyone lose weight. So why use them - especially if safety concerns exist?
The only non-caloric sweetener I recommend is stevia, an herb in the chrysanthemum family native to Paraguay that you can buy in whole-leaf or extract form. The extract - stevioside - is a granular white powder that you dissolve in water and dispense with a dropper. Stevia is safe for diabetics and is widely used as a sweetener around the world, especially in Japan and Brazil. A few drops of the liquid provide the sweetness of an entire cup of sugar.
Andrew Weil, M.D.