The published scientific research behind Hoodia as an appetite suppressant in humans is almost nonexistent. I think it is pretty amazing how an entire industry based on this herb has been built on the equivalent of a house of cards.
Published Research on Hoodia
Do you find it difficult, or even impossible, to find unbiased assessments of actual scientific research about Hoodia on websites that promote this herbal appetite suppressant? You undoubtedly have noticed no end to the repeated story of African bushmen who have used it ‘for thousands of years’ to stop hunger while out hunting. Assuming this is true, then Hoodia is a great product for folks who intend to go hunting in the wilderness for days on end without eating. Proponents of Hoodia, however, have taken a giant leap of faith, equivalent to vaulting the Grand Canyon, to suggest that this herb is important for weight loss among the well-fed and the overweight/obese among us in western civilization.
Celebrity testimonials in support of this notion are now common … nothing like having Leslie Stahl from 60 Minutes or Tom Mangold of BBC News offer up their personal experiences with Hoodia to persuade the public about how good it is, eh? Anybody remember the Oprah endorsement?
What about actual scientific research? Fortunately, we have access to PubMed, which is a public research database (i.e., no cost) provided by U.S. National Institutes of Health. Anyone who knows how to search through the hundreds of thousands of scientific journal articles on this database, then understand what the search results mean, can do so. The challenge is knowing how to find the right information and then understanding enough scientific jargon to interpret what it means.
Regarding Hoodia, all I did was to open up the PubMed search page and put the term ‘hoodia’ into the search box. This search yielded 39 results. Note that, even though PubMed is a research database, sometimes non-scientific articles can creep into the results. If you want, take a look at the complete list that I posted below and see whether you can find any such references. Otherwise, you can read my overview of the list right.
Studies on Weight Loss
The whole idea, of course, is that Hoodia is an appetite suppressant that will help people lose weight. This is what I call a ‘health outcome’ – i.e., actual human studies that examine the effects of Hoodia on a direct change in health, such as weight loss. This is in contrast with what I call ‘biochemical outcomes’, which measure levels cholesterol, enzymes of different kinds, blood sugar, and other such biochemicals. Biochemical outcomes may or may not have to do with health outcomes.
Here is what I see in the list of search results that entail weight loss studies:
Reference 2 (Blom et al., 2011).
Here is the entire list so you can see what I mean. Of course, I have excluded ‘secondary’ research, meaning reviews, commentary, or other articles that did not actually study weight loss in human subjects. Examples are references 7 (2011) and 10 (2010), and of course that completely non-scientific article in Consumer Reports (reference 39, 2006).
And I have excluded all articles regarding biochemical outcomes and other research that had nothing directly to do with weight loss.
1: Dutt HC, Singh S, Avula B, Khan IA, Bedi YS. Pharmacological Review of Caralluma R.Br. with Special Reference to Appetite Suppression and Anti-Obesity. J Med Food. 2011 Dec 22. [Epub ahead of print] PubMed PMID: 22191633.
2: Blom WA, Abrahamse SL, Bradford R, Duchateau GS, Theis W, Orsi A, Ward CL, Mela DJ. 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. Am J Clin Nutr. 2011 Nov;94(5):1171-81. Epub 2011 Oct 12. PubMed PMID: 21993434.
3: Geoffroy P, Ressault B, Marchioni E, Miesch M. Synthesis of Hoodigogenin A, aglycone of natural appetite suppressant glycosteroids extracted from Hoodia gordonii. Steroids. 2011 Jun;76(7):702-8. Epub 2011 Apr 5. PubMed PMID: 21473873.
4: van Platerink CJ, Janssen HG, Graf B, Abrahamse L, Haverkamp J. Quantification of steroid glycosides from Hoodia gordonii in porcine plasma using high performance liquid chromatography-mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci. 2011 Apr 1;879(11-12):819-25. Epub 2011 Feb 23. PubMed PMID: 21398192.
5: Vermaak I, Viljoen AM, Chen W, Hamman JH. In vitro transport of the steroidal glycoside P57 from Hoodia gordonii across excised porcine intestinal and buccal tissue. Phytomedicine. 2011 Jun 15;18(8-9):783-7. Epub 2011 Feb 25. PubMed PMID: 21353512.
6: Scott AD, Orsi A, Ward C, Bradford R. Genotoxicity testing of a Hoodia gordonii extract. Food Chem Toxicol. 2011 Feb 16. [Epub ahead of print] PubMed PMID: 21315789.
7: Vermaak I, Hamman JH, Viljoen AM. Hoodia gordonii: an up-to-date review of a commercially important anti-obesity plant. Planta Med. 2011 Jul;77(11):1149-60. Epub 2011 Jan 21. Review. PubMed PMID: 21259185.
8: Zhao J, Avula B, Joshi VC, Techen N, Wang YH, Smillie TJ, Khan IA. NMR fingerprinting for analysis of hoodia species and hoodia dietary products. Planta Med. 2011 May;77(8):851-7. Epub 2010 Dec 2. PubMed PMID: 21128201.
9: Le Nevé B, Foltz M, Daniel H, Gouka R. The steroid glycoside H.g.-12 from Hoodia gordonii activates the human bitter receptor TAS2R14 and induces CCK release from HuTu-80 cells. Am J Physiol Gastrointest Liver Physiol. 2010 Dec;299(6):G1368-75. Epub 2010 Oct 7. PubMed PMID: 20930049.
10: Whelan AM, Jurgens TM, Szeto V. Case report. Efficacy of Hoodia for weight loss: is there evidence to support the efficacy claims? J Clin Pharm Ther. 2010 Oct;35(5):609-12. doi: 10.1111/j.1365-2710.2009.01116.x. PubMed PMID: 20831685.
11: Wang W, Russell PJ, Clark GT, Lewis D, Cheng KN. A validated bioanalytical method in mouse, rat, rabbit and human plasma for the quantification of one of the steroid glycosides found in Hoodia gordonii extract. Food Chem Toxicol. 2010 Aug 25. [Epub ahead of print] PubMed PMID: 20800086.
12: Madgula VL, Ashfaq MK, Wang YH, Avula B, Khan IA, Walker LA, Khan SI. Bioavailability, pharmacokinetics, and tissue distribution of the oxypregnane steroidal glycoside P57AS3 (P57) from Hoodia gordonii in mouse model. Planta Med. 2010 Oct;76(14):1582-6. Epub 2010 Apr 22. PubMed PMID: 20414860.
13: Figlewicz DP, Ioannou G, Bennett Jay J, Kittleson S, Savard C, Roth CL. Effect of moderate intake of sweeteners on metabolic health in the rat. Physiol Behav. 2009 Dec 7;98(5):618-24. Epub 2009 Oct 6. Erratum in: Physiol Behav. 2010 Apr 19;99(5):691. PubMed PMID: 19815021.
14: Madgula VL, Avula B, Pawar RS, Shukla YJ, Khan IA, Walker LA, Khan SI. Characterization of in vitro pharmacokinetic properties of hoodigogenin A from Hoodia gordonii. Planta Med. 2010 Jan;76(1):62-9. Epub 2009 Jul 28. PubMed PMID: 19639535.
15: Mohlapo TD, Ng’ambi JW, Norris D, Malatje MM. Effect of Hoodia gordonii meal supplementation at finisher stage on productivity and carcass characteristics of Ross 308 broiler chickens. Trop Anim Health Prod. 2009 Oct;41(7):1591-6. Epub 2009 Apr 26. PubMed PMID: 19396624.
16: Shukla YJ, Pawar RS, Ding Y, Li XC, Ferreira D, Khan IA. Pregnane glycosides from Hoodia gordonii. Phytochemistry. 2009 Mar;70(5):675-83. Epub 2009 Mar 19. PubMed PMID: 19303614.
17: Schroers HJ, O’Donnell K, Lamprecht SC, Kammeyer PL, Johnson S, Sutton DA, Rinaldi MG, Geiser DM, Summerbell RC. Taxonomy and phylogeny of the Fusarium dimerum species group. Mycologia. 2009 Jan-Feb;101(1):44-70. PubMed PMID: 19271670.
18: Robb-Nicholson C. By the way, doctor. I’ve seen a lot of Internet ads for Hoodia, a natural supplement that suppresses your appetite. What do you know about it? Does it work, is it safe? Harv Womens Health Watch. 2008 Aug;15(12):8. PubMed PMID: 19115502.
19: Rumalla CS, Avula B, Shukla YJ, Wang YH, Pawar RS, Smillie TJ, Khan IA. Chemical fingerprint of Hoodia species, dietary supplements, and related genera by using HPTLC. J Sep Sci. 2008 Dec;31(22):3959-64. PubMed PMID: 19065611.
20: van Heerden FR. Hoodia gordonii: a natural appetite suppressant. J Ethnopharmacol. 2008 Oct 28;119(3):434-7. Epub 2008 Aug 30. Review. PubMed PMID: 18804523.
21: Avula B, Wang YH, Pawar RS, Shukla YJ, Smillie TJ, Khan IA. A rapid method for chemical fingerprint analysis of Hoodia species, related genera, and dietary supplements using UPLC-UV-MS. J Pharm Biomed Anal. 2008 Nov 4;48(3):722-31. Epub 2008 Jul 15. PubMed PMID: 18718731.
22: van Wyk BE. A review of Khoi-San and Cape Dutch medical ethnobotany. J Ethnopharmacol. 2008 Oct 28;119(3):331-41. Epub 2008 Jul 25. Review. PubMed PMID: 18703129.
23: Avula B, Wang YH, Pawar RS, Shukla YJ, Smillie TJ, Khan IA. Identification and structural characterization of steroidal glycosides in Hoodia gordonii by ion-trap tandem mass spectrometry and liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry. Rapid Commun Mass Spectrom. 2008 Aug;22(16):2587-96. PubMed PMID: 18651714.
24: Madgula VL, Avula B, Pawar RS, Shukla YJ, Khan IA, Walker LA, Khan SI. In vitro metabolic stability and intestinal transport of P57AS3 (P57) from Hoodia gordonii and its interaction with drug metabolizing enzymes. Planta Med. 2008 Aug;74(10):1269-75. Epub 2008 Jul 8. PubMed PMID: 18612942.
25: Schroeder D, Chennells R. Benefit sharing and access to essential health care: a happy marriage? Med Law. 2008 Mar;27(1):53-69. PubMed PMID: 18592881.
26: van Wyk BE. A broad review of commercially important southern African medicinal plants. J Ethnopharmacol. 2008 Oct 28;119(3):342-55. Epub 2008 Jun 3. Review. PubMed PMID: 18577439.
27: Janssen HG, Swindells C, Gunning P, Wang W, Grün C, Mahabir K, Maharaj VJ, Apps PJ. Quantification of appetite suppressing steroid glycosides from Hoodia gordonii in dried plant material, purified extracts and food products using HPLC-UV and HPLC-MS methods. Anal Chim Acta. 2008 Jun 9;617(1-2):200-7. Epub 2008 Jan 18. PubMed PMID: 18486659.
28: Avula B, Wang YH, Pawar RS, Shukla YJ, Khan IA. Chemical fingerprinting of Hoodia species and related genera: chemical analysis of oxypregnane glycosides using high-performance liquid chromatography with UV detection in Hoodia gordonii. J AOAC Int. 2007 Nov-Dec;90(6):1526-31. PubMed PMID: 18193728.
29: Shukla YJ, Fronczek FR, Pawar RS, Khan IA. Hoodigogenin A from Hoodia gordonii. Acta Crystallogr Sect E Struct Rep Online. 2008 Jul 31;64(Pt 8):o1643-4. PubMed PMID: 21203331; PubMed Central PMCID: PMC2962224.
30: Pawar RS, Shukla YJ, Khan IA. New calogenin glycosides from Hoodia gordonii. Steroids. 2007 Nov;72(13):881-91. Epub 2007 Jul 27. PubMed PMID: 17767941.
31: Lee RA, Balick MJ. Indigenous use of Hoodia gordonii and appetite suppression. Explore (NY). 2007 Jul-Aug;3(4):404-6. Review. PubMed PMID: 17681262.
32: van Heerden FR, Marthinus Horak R, Maharaj VJ, Vleggaar R, Senabe JV, Gunning PJ. An appetite suppressant from Hoodia species. Phytochemistry. 2007 Oct;68(20):2545-53. Epub 2007 Jul 2. PubMed PMID: 17603088.
33: Dall’Acqua S, Innocenti G. Steroidal glycosides from Hoodia gordonii. Steroids. 2007 Jun;72(6-7):559-68. Epub 2007 Mar 27. PubMed PMID: 17485103.
34: Pawar RS, Shukla YJ, Khan SI, Avula B, Khan IA. New oxypregnane glycosides from appetite suppressant herbal supplement Hoodia gordonii. Steroids. 2007 Jun;72(6-7):524-34. Epub 2007 Mar 18. PubMed PMID: 17467018.
35: Rader JI, Delmonte P, Trucksess MW. Recent studies on selected botanical dietary supplement ingredients. Anal Bioanal Chem. 2007 Sep;389(1):27-35. Epub 2007 Mar 28. Review. PubMed PMID: 17390125.
36: Avula B, Wang YH, Pawar RS, Shukla YJ, Schaneberg B, Khan IA. Determination of the appetite suppressant P57 in Hoodia gordonii plant extracts and dietary supplements by liquid chromatography/electrospray ionization mass spectrometry (LC-MSD-TOF) and LC-UV methods. J AOAC Int. 2006 May-Jun;89(3):606-11. PubMed PMID: 16792058.
37: Protecting traditional knowledge: the San and hoodia. Bull World Health Organ. 2006 May;84(5):345. Epub 2006 May 17. PubMed PMID: 16710538; PubMed Central PMCID: PMC2627337.
38: Hoodia: lose weight without feeling hungry? Consum Rep. 2006 Mar;71(3):49. PubMed PMID: 16544385.
39: MacLean DB, Luo LG. 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. Brain Res. 2004 Sep 10;1020(1-2):1-11. PubMed PMID: 15312781.
And the Results Are…
I will spend some time in another post explaining how the research was set up, conducted, and analyzed. Suffice it to say for the moment that, if you are looking for scientific research support to justify taking Hoodia for weight loss, you won’t find it in any of the above journal articles.
As mentioned before, it is pretty amazing that Hoodia ever became one of the most popular diet pills in recent times. Marketing and emotional appeal (thanks, Oprah!) took over in the absence of good evidence, I suppose.
Updating Hoodia science (or lack of it),