It fights arthritis! It fights breast cancer, prostate cancer and colon cancer! It fights Alzheimer’s disease! Sound like the usual hype for some dietary supplement scam? Actually, these claims are for a substance that’s readily available in any grocery store. And it’s not some huckster who’s making the claims, but reputable scientists. They’re careful to point out, however, that so far most of the evidence comes from studies in rodents, not humans. So what is this “hot” substance? It’s turmeric, the yellow spice used to add an intriguing flavour to many dishes, curries in particular.
An ancient remedy rediscovered
Turmeric is the ground-up root of an East Indian plant (Curcuma longa) belonging to the ginger family. It usually makes up about 20% to 30% of curry powders, with other spices such as coriander, ginger, chili, black pepper, cumin, mustard, fennel and cardamom contributing the rest. Turmeric’s potential health effects were described thousands of years ago in India’s ancient Ayurvedic system of medicine. It was said to be good for stomach ailments, wound healing and “blood cleansing.” Today in India, the spice is used as a household remedy for sprains and swellings — the sort of problems for which we’d use aspirin or another nonsteroidal anti-inflammatory drug (NSAID). Could turmeric contain some ingredient that has similar activity?
Modern research has identified curcumin, a compound that makes up about 10% of turmeric by weight, as the most likely source of health benefits. Curcumin inhibits the action of the cyclooxygenase-2 enzyme (COX-2), responsible for forming substances that promote inflammation. NSAIDs, including aspirin, also block this enzyme. But curcumin may add another facet to the treatment of inflammation. Turmeric also interferes with the production of a protein known as NF-B, known to stimulate specific genes that control inflammatory substances. Given all of this, we shouldn’t be too surprised that researchers at the University of Arizona have shown turmeric to prevent joint inflammation in rats. A controlled trial with humans using standardized doses of curcumin is sorely needed.
Cancer links
Aspirin and NSAIDs have also been linked with a reduced risk of colon cancer, but the risks associated with these drugs, particularly gastrointestinal bleeding, preclude their use for protection against the disease. Could curcumin offer safer protection? Possibly. In India, where the population consumes an average of about 2 to 3 grams of turmeric a day (containing 200–300 milligrams of curcumin), the incidence of colon cancer is roughly one-eighth that of western countries. This may be more than a chance association, according to a small clinical trial at Johns Hopkins School of Medicine. Five patients with a history of precancerous polyps in their colon were treated with 480 milligrams of curcumin and 20 milligrams of quercetin three times a day. Quercetin is an antioxidant found in apples, onions, tea and citrus fruits that has also been associated with a reduced risk of colon cancer. After six months, all five patients had fewer and smaller polyps! Even though the amount of curcumin used far exceeds the dose provided by any curry, this small study does support the idea that curcumin when consumed regularly may be effective in preventing colon cancer.
Since Indians have one-quarter our breast cancer rate and one-twentieth of our prostate cancer rate, researchers have cast a hopeful eye towards turmeric here as well. Dr. Bharat Aggarwal of the M.D. Anderson Cancer Center in Houston, perhaps the world’s leading authority on turmeric, injected mice with human breast cancer cells from a patient whose disease had spread to the lungs. The mice developed tumours that were surgically removed to simulate a mastectomy. Some of the animals were then treated with curcumin, some with the widely used cancer drug paclitaxel, some with a combination of the two, and some received no treatment. The combination treatment worked the best, with only 22% of the mice developing lung cancer. Amazingly, curcumin alone was more effective than paclitaxel alone.
Researchers at Rutgers University in New Jersey have found similar results for prostate cancer induced in mice. This time they studied the effects of curcumin and phenethyl isothiocyanate (PEITC), an anticancer compound in cruciferous vegetables such as broccoli, cauliflower and cabbage. The mice were injected three times a week for four weeks, and the strongest tumour-slowing effects were found for the combination of curcumin and PEITC. Again, while it’s hard to interpret such experiments in human terms, the study supports the regular consumption of cruciferous vegetables along with turmeric (see recipe, opposite).
Need help remembering this?
Such a diet may even help prevent the buildup of amyloid plaque in the brain, a hallmark of Alzheimer’s disease. Curcumin-fed rats produce less plaque after receiving beta amyloid injections in the brain than rats fed a normal diet. If you have trouble remembering all of this, maybe you could use a little help from turmeric. The curcumin-fed rats also outperformed other rats in maze-based memory tests.
How much is enough or too much?
There isn’t enough known about the effects of turmeric to recommend consuming specific amounts, but it seems safe enough even in large doses. There have been a few isolated reports of an anticoagulant effect and bleeding when turmeric is taken with ginkgo biloba, an herbal supplement that may have memory-enhancing effects. Interaction with prescription drugs is also possible, since curcumin interferes with the action of some enzymes involved in the metabolism of many drugs. Still, researchers at the M.D. Anderson Cancer Center are confident enough in turmeric’s safety to run trials with as much as 8 grams a day in cancer patients.
In any case, adding turmeric-flavoured vegetarian dishes to the diet is surely a good idea. Don’t forget to add some pepper — it increases curcumin absorption a thousand fold! But don’t be messy: while turmeric’s health benefits need further clarification, one sure thing is that it makes for a stain that defies all cleaning techniques known to mankind.
Joe Schwarcz, PhD, is Director of the McGill University Office for Science and Society in Montreal, Québec.
