Origin: Oil from cold-water fish such as mackerel, salmon, herring, tuna, halibut and cod.

Claims: Reduces inflammation and morning stiffness. Treats rheumatoid arthritis, lupus, psoriasis, depression and Raynaud’s phenomenon. Important for brain function and may inhibit RA development.

What we know: Fish oil is an excellent source of omega-3 fatty acids (including EPA and DHA), which block inflammatory cytokines and prostaglandins; they are converted by the body into powerful anti-inflammatory chemicals called resolvins. Fish oil also lowers blood triglyceride (fats that circulate in the blood­stream), protecting against heart disease and reducing high blood pressure.

Studies: EPA and DHA have been extensively studied for RA as well as dozens of other inflammatory conditions, including heart disease, depression, Raynaud's syndrome and lupus. A 2010 meta-analysis found that fish oil significantly decreased joint tenderness and stiffness in RA patients and reduced or eliminated NSAID use. Preliminary studies indicate it may have a similar effect on osteoarthritis. A 2005 study of people with RA showed enhanced positive effects when fish oil supplements were used in combination with olive oil.

Meta-analyses also have shown that fish oil improves depression when taken with conventional antidepressants and in one small study, it increased cold tolerance and time to vasospasm in Raynaud's. 

Dosage: Fish, capsules, softgels, chewable tablets or liquid. For general health, two 3-ounce servings of fish a week are recommended. However, it’s difficult to get a therapeutic dose of fish oil from food alone. To treat arthritis-related conditions, use fish oil capsules with at least 30 percent EPA/ DHA, the active ingredients. For lupus and psoriasis, 2 g EPA/DHA three times a day. For Raynaud’s phenomenon, 1 g four times a day. For RA and OA, up to 2.6 g, twice a day. For depression, 6.6 g daily.

 Due to potentially dangerous levels of mercury, women who are pregnant or hoping to conceive should avoid eating shark, swordfish, king mackerel and tilefish and should eat no more than 8 ounces of albacore tuna each month. Fish oil supplements at normal doses are safe but more than 3000 mg (3 grams) a day increases bleeding risk; avoid taking with blood thinners such as warfarin (Coumadin). Some brands may contain toxic polychlorinated biphenyls (PCBs) or mercury. Look for brands that follow good manufacturing practices.