Caiapo (Ipomoea batatas) is a type of white sweet potato, native to the Brazilian Amazon, that is traditionally eaten raw as a treatment for anemia, high blood pressure, and diabetes. Japanese immigrants in Brazil have popularized the remedy, and extracts of the root are now sold without prescription in Japan as a food additive for the prevention and care of type 2 diabetes.
Results of a study published in the February 2004 issue of the journal Diabetes Care suggest that Caiapo may, indeed, be a natural way to help control blood sugar in patients with type 2 diabetes. In a study from the University of Vienna Medical School in Austria, a team of researchers randomly assigned a group of 61 patients to receive either a daily dose of 4 grams of Caiapo or a placebo. During the 12-week duration of the study, blood-sugar levels (both fasting and following a glucose tolerance test) decreased significantly among the patients taking the Caiapo. No such changes were seen in the patients taking the placebo. The researchers also found that at the end of treatment, the cholesterol levels among the patients who took Caiapo were lower than those in patients receiving the placebo. A small number of patients reported some mild gastrointestinal distress during the study that might have been a side-effect of the Caiapo, although two of the patients in the placebo group reported similar symptoms.
In an earlier, smaller pilot study the same research team saw the same results. That study included only 18 men and lasted for only six weeks. On the basis of results from these two studies, the researchers concluded that Caiapo seems to be an effective way to lower blood sugar.
To my knowledge, Caiapo isn't available outside of Japan and South Korea, although I'm told that some Japanese suppliers ship orders to foreign countries.
Andrew Weil, M.D.