Hoodia

What it is

Hoodia is a succulent, cactus-like plant of the Kalahari Desert whose stems and roots are dried and made into powders, capsules, chewable tablets and teas sold as weight-loss aids. Its supposed active constituent is an oxypregnane steroidal glycoside known as P57. The traditional Kalahari use is often described as hunger suppression, although it may be more accurate to describe hoodia as a food source used mainly to quench thirst. Chemical analysis of commercial products repeatedly finds little or no P57 in them.

What the research says

The human evidence does not support a weight or appetite effect. The one published randomised controlled trial of a purified Hoodia gordonii extract found no significant difference from placebo in ad libitum energy intake or body weight, while the extract was less well tolerated than placebo and was associated with significant rises in blood pressure, pulse, heart rate, bilirubin and alkaline phosphatase. The mechanistic case rests on animal work: in rats, P57 injected into the brain reduced 24-hour food intake by 40-60% and raised hypothalamic ATP content. That is an animal finding and does not establish an effect in people taking a capsule.

Evidence grade: Not supported by the research.

What goes wrong

The same trial found the Hoodia extract was less well tolerated than placebo, with nausea, vomiting and skin sensation disturbances. (Source 1)

• Randomized trial, Moderate certainty.
• Size: 49 women.
• Who: healthy, overweight women.
• How long: 15 days.
• Result: no serious adverse events, but episodes of nausea, emesis and disturbances of skin sensation were more frequent than with placebo.
• Funding: not stated in the abstract.

There were no serious adverse events, but Hg PE was less well tolerated than was the placebo because of episodes of nausea, emesis, and disturbances of skin sensation.

The trial also recorded significant rises in blood pressure, pulse, heart rate, bilirubin and alkaline phosphatase on the Hoodia extract. (Source 1)

• Randomized trial, Moderate certainty.
• Size: 49 women.
• Who: healthy, overweight women.
• How long: 15 days.
• Result: significant (P < 0.05) increases in blood pressure, pulse, heart rate, bilirubin and alkaline phosphatase in the Hoodia group.
• Funding: not stated in the abstract.

Blood pressure, pulse, heart rate, bilirubin, and alkaline phosphatase showed significant (P < 0.05) increases in the Hg PE group.

LiverTox records the small liver-chemistry changes seen in that trial but rates hoodia an unlikely cause of clinically apparent liver injury. (Source 2)

• Expert review, not systematic, Low certainty.
• Size: one small controlled trial plus the absence of published liver injury cases.
• Who: supplement users.
• How long: page last updated 28 March 2018.
• Result: alkaline phosphatase 8-17 U/L and bilirubin 0.2-0.6 mg/dL slightly higher on Hoodia than placebo, ALT unchanged; likelihood score E.
• Funding: US government resource.

In a small controlled trial, serum alkaline phosphatase [8-17 U/L] and bilirubin [0.2-0.6 mg/dL], but not [ALT] levels, were slightly higher in patients on Hoodia compared to placebo, but no patient developed symptoms or clinically apparent liver injury.

Most commercial products labelled as Hoodia contain no detectable P57, the compound the appetite claim rests on. (Source 3)

• Expert review, not systematic, Low certainty.
• Size: 35 commercially available products in the analysis described.
• Who: commercial Hoodia supplements, not people.
• How long: review published 2011.
• Result: 26 of 35 products showed no P57; the remaining nine had low levels.
• Funding: not stated.

Of the 35 commercially available products tested, 26 did not show the presence of P57.

What the evidence supports

In rats, purified P57 delivered directly into the brain reduced subsequent 24-hour food intake by 40-60% and raised hypothalamic ATP content. (Source 4)

• Animal study, Very low certainty.
• Size: not stated in the abstract; rat studies with intracerebroventricular injection and hypothalamic slice punches.
• Who: rats, plus hypothalamic neurons in culture.
• How long: 24 hours after injection; 4 days in the pair-fed low-calorie experiment.
• Result: 24-h food intake reduced by 40-60%; ATP content in hypothalamic neurons increased by 50-150%; in pair-fed rats the 30-50% fall in hypothalamic ATP was blocked by P57AS3.
• Funding: not stated.

In addition, third ventricle (i.c.v.) administration of P57, which reduces subsequent 24-h food intake by 40–60%, also increases ATP content in hypothalamic slice punches removed at 24 h following the i.c.v. injections.

What the evidence does not support

In the published randomised controlled trial, 15 days of purified Hoodia gordonii extract produced no significant difference from placebo in energy intake or body weight. (Source 1)

• Randomized trial, Moderate certainty.
• Size: 49 women (25 Hoodia extract, 24 placebo)
• Who: healthy, overweight women stratified by percentage body fat, resident in a clinic.
• How long: 4-day run-in plus 15-day treatment period.
• Result: mean effects on ad libitum energy intakes and body weights did not differ significantly between groups (P > 0.05)
• Funding: not stated in the abstract; the extract was a commercially developed purified extract (PYM50717) and the trial was conducted under a clinical development programme.

Mean effects on ad libitum energy intakes and body weights did not differ significantly between the Hg PE- and placebo-treatment groups (P > 0.05).

Where the research disagrees

Whether any prospective controlled human trial of hoodia exists

• LiverTox, last updated 28 March 2018, agency-maintained narrative summary: To date, there have been no prospective controlled trials demonstrating an effect of hoodia on food intake or weight management in humans. (Source 5)
• Blom and colleagues, 2011, randomised, placebo-controlled trial in 49 women: Healthy, overweight women, who were stratified by percentage body fat, received either Hg PE (n = 25) or a placebo (n = 24) for 15 d. (Source 1)

How much

• Reference intake: No reference intake exists. Hoodia is a plant extract marketed as a weight-loss aid, not a nutrient, so no body has set an RDA or AI for it. (Source 5)
• Upper limit: No tolerable upper intake level or acceptable daily intake has been set by any body we could reach. The relevant safety information is the trial finding of adverse vital-sign and laboratory changes at the dose tested. (Source 1)
• Studied: The randomised trial gave two servings a day of 1110 mg of purified Hoodia gordonii extract, formulated in a yogurt drink, one hour before breakfast and dinner, for 15 days. (Source 1)

A common belief, and what the research shows

The belief: Hoodia is a proven natural appetite suppressant used for centuries by Kalahari hunters.

What the research shows: Two things undercut this. The traditional use is less clear-cut than the marketing suggests: LiverTox notes "it may be more accurate to say that Hoodia is a food source and was used mostly to quench thirst." And when a purified extract was finally tested against placebo in overweight women, "Mean effects on ad libitum energy intakes and body weights did not differ significantly between the Hg PE- and placebo-treatment groups (P > 0.05)." Most products on sale do not even contain detectable P57.

Questions and answers

What is it?

Hoodia is a succulent, cactus-like plant from the Kalahari Desert. Dried extracts of its stems and roots are made into powders, capsules, chewable tablets and teas and sold as weight-loss aids, often blended with other herbs such as green tea and chromium picolinate. Its supposed active compound is an oxypregnane steroidal glycoside called P57. (Source 5)

What does it do in the body?

The mechanism proposed for hoodia is central appetite suppression by P57. In rats, P57 injected into the third ventricle of the brain cut the next 24 hours of food intake by 40-60% and raised ATP content in hypothalamic neurons, which the authors interpret as an energy-sensing satiety signal. That is animal and laboratory work; it does not show the same thing happens when a person swallows a hoodia capsule. (Source 4)

Is it good or bad for you?

On the published human evidence, it is not good for the purpose it is sold for, and it carries some downside. The one randomised trial found no effect on food intake or body weight, and the extract was less well tolerated than placebo, with nausea, vomiting and altered skin sensation, plus significant rises in blood pressure, pulse, heart rate, bilirubin and alkaline phosphatase over 15 days. (Source 1)

How do you get more of it?

Hoodia reaches people only as a supplement made from dried plant material - powders, capsules, chewable tablets and teas. The trial that tested it used two servings a day of 1110 mg of purified extract in a yogurt drink. Buying more of a labelled product does not reliably mean getting more P57, since most tested products contained none. (Source 1)

If it is harmful, what reduces it?

The literature we reached describes no treatment to clear hoodia; the adverse changes seen in the trial were vital-sign and laboratory changes over a 15-day dosing period rather than persistent injury, and no participant developed clinically apparent liver injury. LiverTox rates hoodia as an unlikely cause of clinically apparent liver injury. (Source 2)

Why might someone be low in it or missing it?

The question does not apply in the usual sense: hoodia is a marketed plant extract, not a nutrient the body needs or makes, so there is no deficiency state. A more practical version of the question is why a hoodia product might contain none of the compound it is sold for - and the answer is that most tested products do not contain detectable P57. (Source 3)

Which whole foods contain it or feed it?

No everyday food contains hoodia. The plant itself was used by Kalahari peoples, and it may be more accurate to describe it as a food source used mainly to quench thirst than as a hunger suppressant. Outside southern Africa it is encountered only as dried stem and root material in supplements. (Source 5)

What happens if you do not have it?

Nothing happens. There is no hoodia deficiency, and the randomised trial found that taking it made no significant difference to how much people ate or what they weighed compared with placebo, so nothing measurable is forgone by not taking it. (Source 1)

How can you test for it?

There is no test of a person's hoodia status, and none would be meaningful for a non-nutrient. Products can be tested: chromatographic fingerprinting (HPTLC, UPLC-UV and the more sensitive UPLC-MS) is used to check whether a product really contains Hoodia material and P57, and these methods are what showed most products do not. (Source 3)

We searched: Searched PubMed and the Hoodia analytical and authentication literature, plus LiverTox, for a validated human assay or biomarker; only product authentication and fingerprinting methods were found.

References

1. American Journal of Clinical Nutrition. Effects of 15-d repeated consumption of Hoodia gordonii purified extract on safety, ad libitum energy intake, and body weight in healthy, overweight women: a randomized controlled trial. 2011. PMID 21993434, DOI 10.3945/ajcn.111.020321. Read the source
2. National Institute of Diabetes and Digestive and Kidney Diseases, NCBI Bookshelf. Hoodia - LiverTox: Clinical and Research Information on Drug-Induced Liver Injury (Hepatotoxicity). 2018. Read the source
3. Planta Medica. Hoodia gordonii: An Up-to-Date Review of a Commercially Important Anti-Obesity Plant. 2011. DOI 10.1055/s-0030-1250643. Read the source
4. Brain Research. Increased ATP content/production in the hypothalamus may be a signal for energy-sensing of satiety: studies of the anorectic mechanism of a plant steroidal glycoside. 2004. PMID 15265618, DOI 10.1016/j.brainres.2004.04.011. Read the source
5. National Institute of Diabetes and Digestive and Kidney Diseases, NCBI Bookshelf. Hoodia - LiverTox: Clinical and Research Information on Drug-Induced Liver Injury (Introduction and Background). 2018. Read the source