Heard the one about the common shampoo ingredient that causes cancer? Or how about the epidemic of blindness among toddlers who accidentally get waterproof sunscreen in their eyes? These absurd fictions used to be the stock-in-trade of ninth-graders bent on frightening the younger kids. But now such tall tales are appearing on the Internet, and many adults are taking them seriously. Consider the latest electronic health scare: about the artificial sweetener aspartame, which is found in everything from Equal to Diet Coke. A widely disseminated e-mail by a “Nancy Markle” links aspartame to Alzheimer’s, birth defects, brain cancer, diabetes, Gulf War syndrome, lupus, multiple sclerosis and seizures. Right away, the long list warrants skepticism. Just as no single chemical cures everything, none causes everything. In this and similar cases, all the Nancy Markles of the world have to do to fabricate a health rumor is post it in some Usenet news groups and let ordinary folks, who may already distrust artificial products, forward it to all their friends and e-mail pals. I received several copies last week, as have many doctors and health organizations. When I searched Altavista www.altavista.com for aspartame AND brain AND seizure AND sclerosis, I learned that Markle’s message is almost identical to an antiaspartame screed first penned under a different name in 1995. None of the specific allegations pan out, however. Among the more outrageous claims: –Aspartame leads to “methanol toxicity.” Not even close. Trace amounts of methanol exist naturally in many fruits and vegetables, and a tiny amount is released whenever the body digests aspartame. But there’s four times as much methanol in a glass of tomato juice as in a can of aspartame-sweetened soda, and our bodies have no trouble handling such a tiny amount. –Aspartame triggers headaches. Wrong again, says Susan Shiffman, a medical psychologist at Duke University who conducted a double-blind placebo-controlled trial of 40 “aspartame sensitive” people. A little probing often revealed the real trouble. One woman, who often ate peanuts with her diet soda, was allergic to peanuts. Another drank too much caffeine. –Aspartame is responsible for the recent uptick in brain-cancer rates. So how do you explain that the trend dates back to 1973, eight years before aspartame was approved in the U.S.? Curiously, Markle didn’t warn against aspartame’s single known health risk. Folks with an uncommon genetic disorder called phenylketonuria shouldn’t consume the sweetener because they cannot metabolize one of its ingredients. Before you decide to believe or, worse, forward an e-mail with serious health claims, do a little checking. Start on the Web with urbanlegends.miningco.com which catalogues the more persistent rumors. Then go to reliable health sites, like mayohealth.org , www.medhelp.org , www.oncolink.org or cancernet.nci.nih.gov or www.navigator.tufts.edu . Otherwise, you might get caught in a web of confusion. For more Web resources on Internet health rumors, see time.com/personal You can e-mail Christine at [email protected]