Fish oil. For years, doctors have known that people who eat fish regularly enjoy substantial protection against heart disease and stroke. A major European randomized clinical trial showed that fish oil also works. As a result of this research, the American Heart Association now recommends 1,000 mg a day of the marine fatty acids DHA and EPA for people with coronary artery disease. It’s also reasonable advice for people with major cardiac risk factors such as high blood pressure, abnormal cholesterol levels, and diabetes. People who eat fish at least twice a week are not likely to benefit from extra fish oil.
While fish oil does appear to protect the heart, its other advertised benefits — ranging from treating depression and bowel inflammation to helping with arthritis — have not been validated. In high doses, fish oil can reduce triglyceride levels; a prescription formulation is now available. If you decide to take fish oil, don’t choose fish liver oil, which has too much vitamin A.
Fiber. Most people think of fiber supplements as a treatment for constipation. But a high intake of fiber has many potential benefits for several health conditions, ranging from heart disease and obesity to hernias, varicose veins, and diverticulitis. The Institute of Medicine recommends 38 grams of fiber a day for men younger than 50, 30 grams a day for older men, 25 grams a day for women younger than 50, and 21 grams a day for women over 50. Whole grains, fruits, vegetables, nuts, and seeds are the best sources of fiber, but many people need supplements to meet these goals. If you need supplementary fiber, consider psyllium, which has the added benefit of lowering cholesterol levels.
Selenium. Few men had heard of this mineral until 1996, when American researchers reported that it appeared to reduce the risk of prostate cancer. Subsequent reports were mixed, raising doubts. Then in 2009, a 35,553-man multinational trial of selenium and vitamin E, alone or in combination, reported that neither selenium nor vitamin E had any benefit against prostate cancer. Selenium also appears to increase the risk of diabetes, and earlier studies dashed preliminary hopes that the supplement might protect against heart attacks. Selenium is not for you.