Hoodia gordonii: Evidence from Clinical Trials
The Efficacy of p57
In truth, few studies have actually been conducted on the efficacy of p57 with most of the evidence concerning its functionality being purely anectodal. All the trials and their data conducted so far are given below.
Evidence from Studies in Rats?
Scientists at Brown University Medical School in Providence, Rhode Island, started their investigation on P57 in Hoodia and how it affects satiety, or fullness, which occurs in the brain, telling us to stop eating.
Because P57 from pure Hoodia gordonii suppresses appetite, finding the biochemical mechanism by which it acts on the brain would be important to future discoveries in obesity. Brown researchers conducted various experiments with normal, healthy rats as they injected small amounts of P57 from pure Hoodia gordonii extract directly into a small cavity in the third intracerebral ventricle their brain located above the hypothalamus, which lies deep in the forebrain. This is a primordial region of the brain, part of the limbic system, that controls numerous drives and functions such as appetite, sex, sleep and mood. It seems that P57 up-regulates hypothalamic ATP (adenosine triphosphate -- the energy compound) by as much as 100%. And it is those high concentrations of ATP that cause the hypothalamus to signal the brain to stop eating.
When the Brown researchers put animals on low-calorie diets, their hypothalamic ATP levels dropped precipitously. But the same animals, given P57 while eating a calorie-restricted diet, had normal hypothalamic ATP. Is this getting interesting? Hoodia may be the answer to the chronic hunger pangs of low-calorie dieting. By boosting ATP levels in the hypothalamus, P57 works just like calories (from sugar, starch, whatever), which also boost ATP levels in the hypothalamus. The obvious difference is that P57 has no calories. On a weight basis, P57 has been found 10,000 times more potent than sugar in suppressing appetite
In these research trials on Hoodia it was found that food intake was reduced by 50-60% during the first 24 hours after the injections, and the effect, which was dose-dependent, lasted for about 24 to 48 hours. Also reported in the paper by Brown researchers, several unpublished studies with rats and humans in which pure Hoodia Gordonii produces decreased appetite that lasted for the duration of the studies (up to 8 weeks). Included in these studies were experiments with obese diabetic rats, in which Hoodia Gordonii was claimed to have produced a reversal of diabetes.
Human Trials.
When the first clinical human trial was conducted with Hoodia, 24 morbidly obese people were placed in a unit which was a closed off area were all that they could do was to read, watch television, interact with each other, and of course eat. Half the people were given Hoodia Gordonii to take, and half were given a placebo. After fifteen days, the group that had been taking Hoodia Gordonii had reduced their calorie intake by 1000 calories a day - despite taking no exercise and not being on a diet.
Admittedly this is a very small trial and most of the evidence for the efficacy come from the Kalahari Bushmen and various reporters who have gone into the Kalahari and eaten raw hoodia. They report an appetite suppressing effect for at least 24h though the doses consumed would have been large (at least 800mg).
Phytopharm, the company currently holding the rights and patents to p57 recently performed a larger trial on a group of 60 overweight individuals and compared the effects of P57 and placebo on their food intake.5 In this short-term study, twice-daily ingestion of P57 was claimed to have produced a dramatic effect: after 15 days, the P57 group had achieved a 30% reduction in caloric intake and a reduction in body fat of 1 kg (2.2 lb).
Does Hoodia gordonii work?
This, of course, is the $64 000. The evidence from rats certainly suggests that hoodia extract does work, as does the small human trials. There aslo seems to be enough anectodal evidence to suggest that Hoodia gardonii is effective at suppressing appetite. But the question remains as to whether it is efficacious as a slimming aid and safe for long-term human consumption.