Monday, November 3, 2008

Can Hoodia help you lose weight?

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.

Phytopharm, an English biopharmaceutical company, was licensed in 1997 to develop P57. In collaboration with Unilever, it hopes to incorporate Hoodia as a food additive in meal replacement products pending clinical studies of its safety and effectiveness. So far, efforts to synthesize P57 on a large scale (an important step in developing an appetite-suppressant drug) haven’t panned out.

There’s no good evidence that the Hoodia products you mention are safe or effective weight-loss agents. Internet vendors often cite a trial showing that after two weeks, subjects taking Hoodia ate 1,000 fewer calories per day than those taking a placebo. But the study involved only 18 people, was never peer-reviewed or published, and was sponsored by Phytopharm. The only published study has been in rats, which consumed less food after P57 was injected into their brains (Brain Research, Sept. 10, 2004). Although that study shed some light on the extract’s activity (it affected neurons in the hypothalamus), the results clearly don’t apply to humans swallowing a pill or capsule.

Also, it’s uncertain what’s actually contained in Hoodia supplements, which aren’t regulated by the FDA. Experts say there aren’t enough Hoodia plants in the world to account for all the alleged Hoodia products on the market. Some may contain little or no Hoodia gordonii, include the wrong plant parts, or use questionable plant sources. We also don’t know the dose needed to achieve weight loss or the drug’s safe upper limit.

There’s simply too little evidence to say whether any of the Hoodia now on the market works or is safe to use. We may know more down the road, but until then, you should probably avoid it.

— Celeste Robb-Nicholson, M.D.
Editor in Chief, Harvard Women’s Health Watch

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