Benefits
Marketed for appetite suppression and weight management
Hoodia is sold as a natural appetite suppressant, but human data do not back this up. In the one well-designed controlled trial, overweight women taking a purified extract for 15 days ate no less and weighed no less than those on placebo, and the extract caused more nausea, vomiting and skin-sensation changes while raising blood pressure and heart rate.
Appetite-suppressant compound (P57) studied in animals
A pregnane glycoside called P57 was isolated from the stems and is treated as the plant's proposed active ingredient. Given by mouth to rats, it lowered food intake and body mass compared with a vehicle control over about eight days. These are animal findings only and have not been shown to produce weight loss in people.
Traditional San use as a hunger and thirst suppressant
San communities of southern Africa have long chewed the stems of Hoodia to blunt hunger and thirst during long hunting trips, which is the origin of its reputation as an appetite suppressant. This is a record of traditional use, not clinical evidence that the plant helps with body weight.
Proposed satiety signaling in brain studies
In rodent studies, P57 injected into the brain raised the energy molecule ATP in appetite-regulating hypothalamus cells and cut later food intake, which researchers proposed as a satiety signal. This central mechanism has been shown only in animals and does not establish an effect on appetite or weight in people.
Mechanism of action
Pregnane glycosides, chiefly P57, as the proposed actives
Standardized Hoodia gordonii extract is largely a mixture of steroidal (pregnane) glycosides, with analyses putting steroid glycosides at roughly three-quarters of the extract by weight. The glycoside P57 is treated as the active and as the marker compound used to judge raw-material and product quality.
Possible central, energy-sensing appetite signal
Laboratory work suggests P57 acts in the brain rather than the gut. In rodents it raised ATP content in hypothalamic neurons by 50 to 150 percent, and brain injections reduced next-day food intake, leading to the idea that hypothalamic energy sensing drives the appetite effect. Shown only in animals.
Sympathomimetic activity linked to cardiovascular effects
A hoodia-containing product showed sympathomimetic (adrenergic) activity in isolated rat tissue experiments, with a beta-adrenergic component. This is a proposed explanation for the raised blood pressure, pulse and heart rate seen with the purified extract in the human trial.
Clinical trials
Randomized, double-blind, placebo-controlled residential trial of Hoodia gordonii purified extract for safety, ad libitum energy intake and body weight. (Blom et al. 2011, Am J Clin Nutr)
49 healthy, overweight women; 25 received the purified extract and 24 placebo, each twice daily before breakfast and dinner for 15 days.
Null for efficacy. Mean energy intake and body weight did not differ from placebo. The extract was less well tolerated than placebo, with more nausea, vomiting and skin-sensation disturbances, and it significantly raised blood pressure, pulse, heart rate, bilirubin and alkaline phosphatase. Registered as NCT01306422.
Isolation of pregnane glycosides from Hoodia stems and oral appetite-suppressant testing in rats. (van Heerden et al. 2007, Phytochemistry)
Laboratory study: two pregnane glycosides isolated from dried H. gordonii stems; one (P57) given to rats by oral gavage at 6.25 to 50 mg/kg.
All doses lowered food consumption over an eight-day period and reduced body mass versus a vehicle control. In a comparison, the compound reduced food intake and body weight, while the drug fenfluramine reduced intake but raised weight. An animal study, not evidence of an effect in people.
Mechanistic rodent and brain-tissue study of the steroidal glycoside P57AS3 and hypothalamic ATP. (MacLean et al. 2004, Brain Res)
Laboratory rodent and brain-slice study; P57AS3 given by brain (intracerebroventricular) injection.
P57 increased ATP content in hypothalamic neurons by 50 to 150 percent, and brain injections reduced subsequent 24-hour food intake by 40 to 60 percent. The authors proposed hypothalamic ATP as an energy-sensing satiety signal. A mechanistic animal study with no human outcomes.
Case report with a systematic literature search on the efficacy of Hoodia for weight loss. (Whelan et al. 2010, J Clin Pharm Ther)
Literature search to March 2009 plus a case of a 57-year-old woman seeking weight-loss advice.
No published, peer-reviewed randomized trials of Hoodia were found; two small unpublished trials reportedly showed promising results with no adverse events. The authors noted major gaps in dose, duration and safety, and that some commercial products may contain no Hoodia at all.
Pharmacological study of a Hoodia gordonii product for sympathomimetic activity to explain reported cardiovascular effects. (Roza et al. 2013, Biomed Res Int)
Laboratory study using isolated rat uterine-ring tissue and chromatographic comparison with authentic plant material.
The product relaxed smooth muscle with a substantial component mediated through beta-adrenergic receptors, indicating sympathomimetic activity, and contained genuine Hoodia extract. The authors proposed this as a mechanism for the increased blood pressure and pulse rate reported with Hoodia products. A laboratory study.