Dear PH I received a number of letters from readers expressing concern over my column on mangosteen, a fruit native to Southeast Asia. The original question dealt with an individual who had been hearing wonderful things about mangosteen juice; there was a request to find out if there was any substance to the claims for health and curative benefits. I reported that mangosteen looked like a great food, but I could find no research to support the idea that it offered any special benefits. As with your note, each letter claimed that I had failed to find the plentiful research evidence attesting to the unique powers of this fruit.
My original search was for peer-reviewed scientific studies. I could not find any clinical studies, which is research testing the effects in people. I did find a number of in vitro studies, and not much more. In vitro (Latin for “in glass”) research involves work done on isolated cells or cellular components in a controlled environment outside of a living organism. (You may be familiar with the term “in vitro fertilization,” in which an egg is fertilized outside of a woman's body.) In vitro research contributes to our understanding, but it says little about how a substance might react in the whole organism.
If, for example, an extract of mangosteen would be able to kill cancer cells in a test tube, this cannot be used to substantiate a claim that drinking the juice will have the same effect in the human body. Salt in a high enough concentration can kill cancer cells in a test tube. This doesn't make salt a cure for cancer.
Positive in vitro findings might lead to a testing of the substance in an animal model. Depending on what researchers find, it might then be appropriate to conduct studies with people. Only at this point could you begin to make statements concerning what might take place in humans. I could not find such research using mangosteen. Research is expensive and it takes time. We might have these studies some day, but not yet.
You mentioned a study conducted at Ohio State University. This research concerned the use of isolated mouse cells growing in culture. The study reported how cells exposed to alpha mangostin, a component extracted from mangosteen, did not show expected precancerous changes after the cells had been exposed to a known carcinogen. Again, the study provided interesting and possibly important data, but such research cannot predict what would happen if a mouse were to drink the complete juice, let alone how this substance or the juice might act in people.
Before we get over-excited about new products, we need to keep in mind that there have been similar laudatory findings for other foods, including pomegranate, raspberries, green tea, cherries, blueberries, grapes, olive oil, almonds and even chocolate and coffee. The list is long. Plants that grow in the sun have to produce self-defense compounds or they would never have passed the test of time. Including such foods in our diets can be protective for us as well. I have no desire to knock mangosteen or its juice; that's not what this is about. At this point it looks as though this food has the right stuff to be a proud member of the “healthful foods” club. But until we have a solid foundation, we must tread carefully before we attempt to elevate this food above others.