Hoodia Thought?

What could erstwhile Playmate of the Year Anna Nicole Smith and the African San Bushmen of the Kalahari Desert possibly have in common? One thing: They both take in a previously esoteric plant-derived substance called Hoodia gordonii.

A late November telecast of the CBS news program ’60 Minutes’ showcased the interesting effects of extracts of the Hoodia plant, which is indigenous to South Africa and looks like a cactus but is a member of the milkweed family. It has an appetite-suppressing effect in the brain that’s reportedly 10,000 times more potent than that of glucose. That’s significant because one theory of appetite control suggests that the urge to eat is turned off when cells in the brain’s appetite center in the hypothalamus sense the presence of glucose, which increases following a meal.

Bushmen of South Africa have used Hoodia for their hunting treks in the Kalahari for about 27,000 years. Yet the effects of Hoodia were disclosed to agents of the South African government only a few years ago, whereupon the agents promptly acquired a patent for it. They then sold the rights to research Hoodia to a British pharmaceutical firm called Phytopharm. After spending millions on research, Phytopharm finally isolated a substance that was called P57. It was the 57th plant compound the company investigated for commercial development.

Phytopharm subsequently sold the Hoodia use patent to the giant pharmaceutical firm Pfizer in 1998. Pfizer conducted a number of experiments involving both animals and humans. In the animal studies P57 extracts completely inhibited the appetites of even starving rats. A human study found that those on Hoodia extracts reduced their total daily intake by an average of 1,000 calories with no hunger sensations whatsoever. Despite the excitement generated by Hoodia, there is scant clinical literature on either its effectiveness or safety. Existing data show that P57 is similar in structure to drugs called glycosides, the most prominent of which is digitalis, used to treat heart failure. Like P57, digitalis was originally derived from a natural source, the foxglove. A side effect of digitalis is loss of appetite.

The prevalent theory of how Hoodia extract curtails appetite posits that because it’s so much more potent than glucose in interacting with the brain’s appetite center, the brain is fooled into thinking you just ate a full meal and responds by turning off the appetite. A study in which P57 was injected directly into the brains of rats found that the compound rapidly increased the ATP, or adenosine triphosphate, content of the hypothalamus by 50 to 150 percent.1 That’s significant because ATP is the most basic energy source in the human body. All foods are eventually converted into ATP.

Unlike other substances touted for weight loss, Hoodia has no stimulant effects, so there’s no danger of adverse cardiovascular or other side effects related to stimulant activity. The problem with Hoodia is that it turns off thirst sensations, which could be dangerous, especially in light of the limited research into its long- and short-term health effects. While Bushmen have used sap from the Hoodia plant as food for thousands of years, they’ve never used it as a weight-loss compound. Preliminary animal studies show Hoodia to be remarkably free of side effects considering its potent effect on appetite.

Pfizer abandoned the commercial development of Hoodia because it was too costly to extract P57 from the plant in mass quantities, and making it synthetically was cost prohibitive. So Pfizer sold the Hoodia commercial rights back to Phytopharm. Lost in the mix were the San Bushmen, who had discovered Hoodia in the first place. The initial excuse for attempting to deprive the Bushmen of monetary gain from Hoodia sales was the perception that all the Bushmen were extinct. In fact, there are about 100,000, and a lawyer intervened to help these impoverished people. At least now if Hoodia becomes a commercial success, they’ll gain some income.

1 MacLean, D.B., et al. (2004). Increased ATP content/production in the hypothalamus may be a signal foe energy-sensing of satiety: studies of the anorectic mechanism of a plant steroidal glycoside. Brain Res. 1020:1-11.