Hoodia -- a succulent, not a cactus, as it's often erroneously described. Experts familiar with it say hoodia tricks your brain into thinking you're full. But they acknowledge that published, scientific studies proving hoodia works long-term are sparse.
Because it is sold as a dietary supplement, hoodia escapes the level of scrutiny the FDA gives prescription drugs and medications sold over the counter.
Now, the plant native to the Kalahari Desert is being imported in heaps to slim down hefty Americans. Media reports and word-of-mouth is fueling this latest craze, not to mention thousands of email spams.
Widely sold over the Internet and in health food and discount stores, Hoodia gordonii is typically offered in capsules or tablets, but is also available in milk chocolate chews. A 30-day supply often costs $35 and up.
Despite booming sales -- one manufacturer claims its sales alone reached $20 million in the past year -- the unanswered question is: Where's the proof this stuff works?
It's taken years for overweight Americans to discover what the South African bush people knew innately -- or so the story goes. For eons, the bush people have nibbled a native succulent plant called Hoodia gordonii -- and stayed slim. No fretting (apparently) about fitting into "skinny jeans" or advancing a belt notch.
Hoodia does have some evidence to back it up, says Mark Blumenthal, founder and executive director of the American Botanical Council, a nonprofit research organization in Austin, Texas. He cites one laboratory study but says the evidence is not conclusive.
"We can only say the evidence available to us right now, which is considered inadequate, suggests that there is some type of appetite-suppressing mechanism in some of the naturally occurring chemicals in hoodia," Blumenthal says. He adds that his organization has not received any consumer reports of safety problems with hoodia use.
The laboratory evidence Blumenthal refers to was produced by David MacLean, MD, an adjunct associate professor at Brown University in Providence, R.I., and a former researcher at the pharmaceutical giant, Pfizer. In a report published in the Sept. 10, 2004, issue of Brain Research, MacLean reported that a molecule in hoodia, called P57, likely has an effect on the brain's hypothalamus, which helps regulate appetite. His study was done in animals.
In an email response to WebMD, MacLean says a cousin of hoodia's P57 molecule may eventually prove to be the better answer. "A chemical within that class of molecules has real potential to reduce appetite," he says. "I'm less confident regarding the hoodia molecule itself for reasons relating to its metabolism [absorption and breakdown] in humans."
About the time MacLean's article was published, Richard M. Goldfarb, MD, a doctor in Morrisville, Pa., conducted a study of Hoodia gordonii on people and found it effective. His study was small, just seven people, says Goldfarb, medical director of Bucks County Clinical Research, an organization that conducts studies for pharmaceutical and other companies.
"Hoodia gordonii works within the satiety center of the brain by releasing a chemical compound similar to glucose but up to 100 times stronger," Goldfarb says in his written report. "The hypothalamus receives this signal as an indication that enough food has been consumed and this in turn decreases the appetite."
Phytopharm, a U.K.-based company developing hoodia weight loss products with Unilever, the giant food and consumer products company, cites a 2001 study on its web site that it did, in which the plant extract caused a reduction in average daily calorie intake and in body fat within two weeks. Caloric intake dropped by about 1,000 a day after about two weeks, according to the study.
None of this is enough science to satisfy experts at the Mayo Clinic. In an online report on weight loss pills, published in March, the clinic's bottom line on hoodia was: "No conclusive evidence to support the claim [of appetite suppression]."
Other doctors are skeptical, including Adrienne Youdim, MD, medical director of the Comprehensive Weight Loss Program at Cedars-Sinai Medical Center, Los Angeles. When asked by patients about hoodia and whether they should try it, Youdim tells them: "There is no [published scientific] data to support its use. But, similarly, there is no data suggesting adverse effects. It's kind of uncharted territory." She doesn't recommend using the product.
Michael Steelman, MD, chairman of the board of trustees for the American Society of Bariatric Physicians, treats obese patients in his practice in Oklahoma City, and many of them ask him about hoodia. "I remain pretty skeptical," he says. "Some of my patients have tried it, but I haven't had any who felt like it was helpful to them."
On one point nearly everyone agrees: there's plenty of fake hoodia out there. MacLean is especially suspicious that hoodia products sold over the Internet aren't the real thing or don't have enough hoodia in them to work. It's "buyer, beware," Blumenthal says. "There appears to be much more hoodia offered in North American markets than the production ability of the South African markets."
If you decide to try hoodia, "Buy at a reputable store and buy a reputable brand," suggests Michael McGuffin, president of the American Herbal Products Association, an industry group. If it seems too cheap to be good, it probably is, he says.