By the way, doctor: Can Hoodia help you lose weight?

Q. I've seen a lot of Internet ads for Hoodia, a natural supplement that suppresses your appetite. What do you know about it? Does it work, and is it safe?

A. Hoodia is a succulent plant that grows in the Kalahari Desert in southern Africa, where the indigenous people (San) are said to chew the plant to help stave off hunger. The Hoodia species with purported appetite-suppressing properties is Hoodia gordonii. In the 1990s, researchers isolated an extract of the plant called P57, which is thought to stimulate feelings of satiety in the brain.