The Commentary by Dr. David Morton deserves additional background to place mangosteen research in accurate context as a fruit with only rudimentary support for its potential health benefits. Dr. Morton states there is Asian documentation for significant medical benefits of mangosteen, but all the references he provides (his references 2-7) are from traditional medicine for which there exists no confirmation in western science. Dr. Morton also gives the example of a human study reported 77 years ago in Singapore for anti-inflammatory and anti-infective properties of mangosteen. This research also has not been confirmed nor is there sufficient modern research to conclude such specific therapeutic benefits would apply.
Mangosteen Xanthones.
Dr. Morton emphasizes mangosteen xanthones as an important phytochemical group present in the fruit exocarp(1). Xanthones are not unique to mangosteen but rather are common among many plant species and have been of interest over decades for commercial use as insecticides (2).
Xanthones are also not a predominant constituent of mangosteen rind but rather one of many other polyphenols including protocatechuic acid, anthocyanins, oligomeric proanthocyanidins and tannins (3-6).
Mangosteen Health Benefits?
Dr. Morton states there are “more than 100 studies published on the medicinal benefits of the mangosteen fruit.”(7) This is exaggerated, in our opinion, as there are no studies confirming any medical benefits of mangosteen. In the database of PubMed, there are only 81 biological citations for mangosteen over its publication history beginning in 1979 (as of May 2009), all still at a preliminary level precluding any definition of their importance to humans.
Research interest for mangosteen is increasing, however, as 75% of the total number of mangosteen publications have occurred since 2000 on topics such as antioxidant characteristics of xanthones and in vitro disease models. Still, this level of research places mangosteen phytochemicals at the earliest stages of investigation, many years from building sufficient scientific substantiation to justify human studies that may validate a health benefit (8).
There is no scientific evidence xanthones or any other mangosteen extracts have significance in human biology (9-12).
No health authority supports consumption of processed mangosteen products to gain health benefits or treatment of any human disease condition, certainly not for specific treatment of dysentery or diarrhea as stated by Dr. Morton. University of California-Berkeley, the Mayo Clinic, American Cancer Society, Dr. Ralph Moss, and the Center for Science in the Public Interest have published articles declaring that mangosteen juice has no evidence for benefit.
Promoting XanGo Juice.
As the Medicus study using human subjects mentioned by Dr. Morton has not yet been subjected to scientific peer review and publication, it is not possible to assess the quality of this work. In our opinion, if it is going to be referenced, it should be fully disclosed for all to see and judge. Statements about the importance of what was found when no one else can see the complete design and results are valueless -- all the more so if there is possible promotion of XanGo involved. And if it is too early to draw any conclusions based on unpublished data, then it should not have been mentioned at all. Most specifically, if any effect were to be found positive in subjects using XanGo juice, the result could not possibly be attributed specifically to mangosteen because there are 10 different fruits in the XanGo juice blend. Accordingly, we believe there is no value of this study to mangosteen science.
Conflict of Interest?
We believe the only way to determine the objective and factual value of a critique by Dr. Morton is for him to make a full disclosure of any conflict of interest between scientific objectivity and his possible commercial involvement with XanGo. Failure to do so could raise questions about his commentary that could have been avoided.
Any discourse where someone supports his premise with scientific references, as should happen for mangosteen science, shines a light on the specific citations chosen; they are therefore all the more important to examine closely in this context of whether Dr. Morton's choices for references are relevant to mangosteen's application as a healthful fruit. The scrutiny becomes even more important when a commercial product -- XanGo juice – has been promoted by him previously (1).
The line between science and promotional hyperbole is actually easy to see. Any appearance of trying to mislead through lack of disclosure (if this was the case) obviously would erode the credibility of Dr. Morton. After all, there is no scientific evidence or regulatory approval that mangosteen fruit, XanGo juice, its xanthones or other mangosteen polyphenols have any significance at all to human health, yet a non-scientific, unsuspecting consumer might come to a different conclusion reading Dr. Morton's commentary.
Deterring Misinformation.
For consumers who would consider using mangosteen products for a health benefit, cautions should apply like those emphasized by the FDA and Federal Trade Commission that scientific substantiation and regulatory approval are necessary to affirm a position for health claims on botanical products (13,14). The FTC document is meant to deter misinformation used to promote dietary supplements like XanGo juice with unsubstantiated science and no proven health benefits (14). As the FTC site advises, consumers should “add a dose of skepticism” and be aware of how to spot false claims (14) to separate conspicuous marketing from actual science.
References
1. FDA warning letter to XanGo LLC, September 20, 2006, quotes from Dr. David A Morton, page 4, http://www.fda.gov/foi/warning_letters/archive/g6031d.pdf
2. Steiner LF, Summerland SA. Xanthone as an ovicide and larvicide for the codling moth. J Econ Entomol 1943 36:435-439.
3. Fu C, Loo AE, Chia FP, Huang D. Oligomeric proanthocyanidins from mangosteen pericarps. J Agric Food Chem. 2007 Sep 19;55(19):7689-94, http://www.ncbi.nlm.nih.gov/pubmed/17715900
4. Zadernowski R, Czaplicki S, Naczk M. Phenolic acid profiles of mangosteen fruits (Garcinia mangostana). Food Chem. 2009 Feb 1; 112(3):685-689
5. Palapol Y, Ketsa S, Lin-Wang K, Ferguson IB, Allan AC. A MYB transcription factor regulates anthocyanin biosynthesis in mangosteen (Garcinia mangostana L.) fruit during ripening. Planta. 2009 Mar 22. [Epub ahead of print], http://www.ncbi.nlm.nih.gov/pubmed/19306102
6. Bin Osman M, Rahman Milan A. (2006) Mangosteen - Garcinia
mangostana. Southampton Centre for Underutilised Crops, University of Southampton,
Southampton, UK, http://www.icuc-iwmi.org/files/Publications/Mangosteen_Monograph.pdf
7. XanGo Juice, http://www.xango.com/products/xango-juice and Supplement Facts, http://rs.xango.com/downloads/xango4.0/xango_supplement_facts.pdf
8. PubMed, search results for 'mangosteen', May 5, 2009, http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=mangosteen&tool=gquery%2F
9. Gross PM, Crown I. Is mangosteen a superfruit? Nutrient and antioxidant properties, Natural Products Information Center, February 5, 2007, http://www.npicenter.com/anm/templates/newsATemp.aspx?articleid=17613&zoneid=43
10. Obolskiy D, Pischel I, Siriwatanametanon N, Heinrich M. Garcinia mangostana L.: a phytochemical and pharmacological review, Phytother Res. 2009 Jan 27, http://www.ncbi.nlm.nih.gov/pubmed/19172667
11. Associated Press, Is $40 ‘super fruit’ juice really good for you? Business claims drink offers immunity boost — but hasn’t proven it, MSNBC, http://www.msnbc.msn.com/id/23071982//
12. Science, non-science and nonsense, Mangosteen.com, http://mangosteen.com/Sciencenonscienceandnonsense.htm
13. US Food and Drug Administration, Office of Nutritional Products, Labeling and Dietary Supplements, Center for Food Safety and Applied Nutrition, Guidance for Industry: Substantiation for Dietary Supplement Claims Made Under Section 403(r)(6) of the Federal Food, Drug, and Cosmetic Act, Division of Dockets Management (Docket No. 2004D-0466), November, 2004, http://www.cfsan.fda.gov/~dms/dsclmgui.html
14. US Federal Trade Commission, Facts for Consumers, 'Miracle' Health Claims: Add a Dose of Skepticism, October, 2001, http://www.ftc.gov/bcp/edu/pubs/consumer/health/hea07.shtm