The active constituent is known as curcumin. It has been shown to have a wide range of therapeutic actions. First, it protects against free radical damage because it is a strong antioxidant.^{1, 2} Second, it reduces inflammation by lowering histamine levels and possibly by increasing production of natural cortisone by the adrenal glands.³ Third, it protects the liver from a number of toxic compounds.⁴ Fourth, it has been shown to reduce platelets from clumping together, which in turn improves circulation and may help protect against atherosclerosis.⁵ There are also test-tube and animal studies showing a cancer-preventing action of curcumin. In one of these studies, curcumin effectively inhibited metastasis (uncontrolled spread) of melanoma (skin cancer) cells.⁶ This may be due to its anti-oxidant activity in the body. Curcumin inhibits HIV in test tubes, though human trials are needed to determine if it has any usefulness for treating humans with this condition.⁷

A preliminary trial in people with rheumatoid arthritis found curcumin to be somewhat useful for reducing inflammation and symptoms such as pain and stiffness.⁸ A separate double-blind trial found that curcumin was superior to placebo or phenylbutazone (an NSAID) for alleviating post-surgical inflammation.⁹

While a double-blind trial has found turmeric helpful for people with indigestion,¹⁰ results in people with stomach or intestinal ulcers have not shown it to be superior to a placebo and have demonstrated it to be less effective than antacids.^{11, 12}

Preliminary research indicates a possible benefit of oral curcumin supplementation (375 mg of turmeric extract with 95% curcuminoids three times daily for 12 weeks) for chronic anterior uveitis (inflammation of the iris and middle coat of the eyeball).¹³