Hoodia: Lots of Hoopla, Little Science

Few studies support the promise of the South African appetite suppressant, but believers abound.

By Kathleen Doheny
WebMD Weight Loss Clinic - Feature

Reviewed by Louise Chang, MD

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.

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 weight loss 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?

Hoodia -- a succulent, not a cactus, as it's often erroneously described -- has lots of hoopla, but little science, at least little published science, as even advocates admit. 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.

The Science

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.

Goldfarb's Study

Goldfarb studied DEX-L10, the 500-milligram hoodia capsules sold by Delmar Labs. Goldfarb did the study for the manufacturer but says he was not paid for the research. "I did it as a service to them," he says.

In Goldfarb's study, the seven overweight participants were told to take two Hoodia gordonii (DEX L-10) capsules a day, eat a balanced breakfast and take a multivitamin, and keep other eating and exercise habits unchanged. The participants' starting weights ranged from 193 to 345 pounds. They lost, on average, 3.3% of their body weight, Goldfarb says. The median loss over the 28-day study was 10 pounds (half lost more, half less).

Most of the participants reported their caloric intake dropped to less than half within a few days after starting hoodia, and they didn't report side effects such as jitteriness or insomnia, Goldfarb says.

The study was not published in a scientific journal nor presented at a medical meeting, Goldfarb says, because it was conducted as an "efficacy" study, trying only to find out if the product actually works.

Goldfarb is recruiting volunteers for a second, larger study, commissioned by Delmar Labs, which he hopes to begin by year's end.

"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."



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