Green tea seems to be appearing everywhere these days, in practically every form imaginable: green tea ice cream, green tea cookies, green tea soda, green tea angel food cake (with an almost freakishly green color)—even green tea chocolate-covered cherries. Much of the cause of this rise is green tea's health benefits, which are the stuff of legend. Now people with rheumatoid arthritis and diabetes can lift their cups high and toast green tea—some of that legend has been proved in the laboratory. At two recent conferences, two groups of researchers presented intriguing data on a compound found in green tea, epigallocatechin-3-gallate (EGCG), the same stuff that's supposed to make it possible for some energy drinks to have a negative number of calories.
Investigators at the University of Michigan have demonstrated that EGCG reduces the production of specific molecules that contribute to inflammation and joint damage in people with rheumatoid arthritis. The research focused on a type of cell called a synovial fibroblast, which helps to lubricate the lining of our joints. Normally, this lining keeps our joints moving smoothly and pain free. But in some rheumatic disorders, molecules like interleukin-1b stimulate synovial fibroblasts to produce other molecules that start or extend a process of joint inflammation and destruction. Here’s where the green tea comes in. When the investigators pregrew synovial fibroblasts in a dish, treated them with EGCG, and then stimulated them with interleukin-1b, they found a significant reduction in the production of bone-eroding molecules.
Other recent research suggests that if you have diabetes, then green tea just might be your drink—at least if you're a rat. Researchers at the Karolinska Institutein Sweden compared the effects of EGCG with those of the antidiabetes drug Avandia in rats with diabetes. EGCG improved the animals' glucose levels as well as the amount of insulin they made in response to a glucose load. EGCG wasn’t as potent as Avandia, but it did have some of the same beneficial effects.
These results, as well as other studies on green tea and EGCG, certainly open up new areas of investigation. While none of these studies necessarily proves that green tea will treat arthritis or diabetes in people, it certainly wouldn’t hurt to have a cup or two a day (as long as it's not boiling when you drink it). However, I do think it’s too early to recommend EGCG as a medication or a dietary supplement. We still need more information on how it works in people and whether it has any unanticipated side effects.
I’m always excited when scientific discoveries come from unexpected places. It makes medicine more fun, and it’s a good lesson in academic humility. I only wish someone could find a molecule that provided great health benefits and was found only in key lime pie. I'll let you know if anything new emerges in the medical literature—or in the bakery.
Robert W. Lash, M.D. is an associate professor of internal medicine at the University of Michigan Medical School. His clinical interests include thyroid disease, diabetes, endocrine disorders in pregnancy, osteoporosis and metabolic bone disease, and medical education. A member of the LLuminari team of experts, a board certified internist and endocrinologist, Dr. Lash has an active clinical practice and is a hospitalist at the University of Michigan.
