Few New Year’s resolutions are more popular than the one to lose weight. The inability to do so is one of the most common complaints heard by health-care providers. “I don’t really eat that much” and “I dieted and worked really hard and didn’t lose a pound” are statements repeated every day in offices and clinics around the world. The desire to be thinner fuels an astounding $40 billion a year in consumer spending on weight-loss products.1 In light of the FDA ban on the popular ephedra products, diet enthusiasts are eager for new and more effective weight-loss supplements. Around the same time that the ban on ephedra went into effect, Hoodia gordonii products were introduced in the United States as appetite suppressants. As with most new weight-loss products, consumer interest and sales accelerated rapidly.

Background

The baked sands of the Kalahari Desert of South Africa are home to a tribe of natives known as the San Bushmen. For centuries, they have eaten the bitter, pulpy flesh of the H. gordonii cactus to stave off hunger during their long hunting forays.2 With both food and water scarce in the outlying bush of their homeland, these hunters routinely chewed the pulp of the hoodia spikes in order to survive.

Hoodia is a stem succulent that looks very much like a cactus but is unrelated to the cactus family. It is a finicky plant that thrives in the arid, hot climate of the desert. Older, mature plants produce large flesh-colored to pale purple blossoms with a strong, unpleasant odor similar to that of rotting meat. Growing in clumps with spikes as tall as three feet, these unusual plants are a protected species typical only of the Namib Desert. Other common names for hoodia include “Bushman’s hat” and “queen of the Namib.”3

In 1937, a Dutch anthropologist noted the San Bushmen’s use of hoodia to suppress appetite.4 Then in 1963, the Council for Scientific and Industrial Research (CSIR), South Africa’s premier scientific research and development organization, began actively studying hoodia.4 Animal tests showed promise in appetite suppression.

Soon thereafter, CSIR scientists collaborated with the British company Phytopharm and isolated what has since been dubbed hoodia’s active ingredient, “p57.” This steroidal glycoside was patented in 1965 and leased to Phytopharm. Millions of dollars in research later, Pfizer sublicensed rights to hoodia and p57 development in 1998.4

Again, after extensive toxicology work, Pfizer released the development rights back to CSIR in 2002 after concluding that it was not immediately feasible to isolate the active ingredient (p57) in such a way that would not produce hepatotoxicity in humans.3 In the latest episode of this complicated chain of possession, CSIR joined forces with Unilever, which plans to begin putting hoodia into some of its OTC weight-loss products.3

Scientific data

The hypothesized mechanism of action of hoodia p57 relates to the glucose-sensing cells of the hypothalamus in the mid-brain.2 Normally, as an individual eats and blood sugar levels rise, these hypothalamic cells sense the glucose and proportionately relay a level of satiety to the rest of the brain.2 Hoodia p57 is purported to intervene in this feedback loop and affect the glucose-sensitive cells of the hypothalamus with an intensity 10,000 times that of normal glucose.2 Hence a feeling of complete satiety ensues and persists for several hours.

A search of the literature revealed no human randomized clinical trials concerning H. gordonii. Phytopharm conducted one limited trial of 18 morbidly obese individuals randomized to placebo or hoodia, but this trial was neither peer- reviewed nor published. One trial involving rats did show promising data on appetite suppression.4

Safety, efficacy, and dosage

The scant data available on p57 hoodia show a relatively positive safety profile (except for concerns over hepatic metabolism problems in certain forms). Anecdotal reports abound of persons eating the raw plant and suffering absolutely no toxic effects. Perhaps the most notable of these was filed when reporter Lesley Stahl took her 60 Minutes crew to South Africa and ate some of the pulpy cactus. After pronouncing the plant was “cucumbery in texture,” Stahl went on to proclaim a total lack of hunger or thirst for the entire day afterward.4

Unfortunately, since the actual development of p57 has been forestalled, there are no reliable safety, efficacy, or dose-range data available. Possibly the most serious concern is that of impostor products. One source estimated that as many as 80% of the products marketed as containing hoodia are contaminated or completely counterfeit.4 A cursory Web search reveals numerous sites promoting hoodia, all advertising a different brand, dose, and formulation of the proprietary plant. However, considering that the sole rights to the hoodia plant and its commercialization belong to the San Bushmen, true hoodia products should be expected to be relatively difficult to locate.

Again, no specific dose or formulation is known, and no information regarding drug interaction is available. Formulations currently in use include capsules, extracts, tinctures, teas, powders, and transdermal patches. One study involving rats estimated that true hoodia could reduce daily intake by as much as 1,000 calories.4 Such a drastic figure raises obvious safety concerns about using this product. Unintentional anorexia, malnutrition, and dehydration could conceivably occur.

Summary

While H. gordonii has exciting potential as an appetite suppressant, it is a long way from being a safe, recommended supplement. There is a complete lack of sufficient safety and dosage data, making it a compound no practitioner should recommend. Hopefully, future research will further develop this lowly desert plant into a clinically safe and efficacious tool in the weight-management arsenal. But for now, scattered tabloid reports and advertisements are not adequate prescribing information. If Unilever continues with its plans to add hoodia to some of its products this year, clinicians will have more definitive information on the safe use of this intriguing phytochemical.

References

1. CBS News. African plant may help fight fat. Available at www.cbsnews.com/stories. Accessed January 9, 2008.

2. BBC News. Sampling the Kalahari Hoodia diet. Available at http://news.bbc.co.uk/2/hi/programmes. Accessed January 9, 2008.

3. Wikipedia. Hoodia. Available at http://en.wikipedia.org/wiki/Hoodia. Accessed January 9, 2008.

4. About.com. Hoodia gordonii review. Available at http:// altmedicine.about.com/od/popularhealthdiets. Accessed January 9, 2008.