Omega-3 fatty acids, one of the most popular supplements today, are essential to building cell membranes. Because the body doesn't naturally produce omega-3s, we have to get them through diet, but few foods contain significant amounts. Fatty fish is high in omega-3s – a half fillet of wild salmon contains up to 4,000 milligrams – but if you don't eat at least two servings weekly or consume flaxseeds, nuts, or canola oil daily, you're most likely deficient.
Doctors say omega-3 supplements are key not only to cell health but also to keeping the heart healthy by reducing blood triglycerides, which can cause arteries to harden. The evidence is so pervasive that in 2004 the FDA approved one of its rare health claims, allowing manufacturers to print on everything from fortified juice and eggs to chocolate bars that "omega-3s may lower the risk of coronary heart disease." Since then, more research supporting the claim has been conducted, including a 2008 Mayo Clinic study of 32,000 people showing that those who supplemented with 850 to 1,800 mg of omega-3s daily have up to 45 percent reduced risk of cardiovascular problems like heart attacks, and that taking a combination of supplemental omega-3s and statin drugs is more effective at treating heart disease than statins alone. Research continues to mount showing omega-3s can also help protect against arthritis, depression, dementia, and other cognitive problems. "Most Americans are deficient in omega-3s, which may account for the rise of asthma, coronary heart disease, many cancers, and neurodegenerative disease," Weil says.
How to take them: Most experts say to take 1,000 to 2,000 mg daily. Look for a supplement that delivers at least 500 mg each of EPA and DHA, the two active fatty acids in omega-3s. Fish oil is better than plant-derived supplements, which don't contain both acids.
Krill, a shrimp-like crustacean, has become a trendy oil source, as larger fish like cod and herring can be contaminated with mercury. But there's growing concern that krill is being overfished, endangering whales that rely on it for food. Doctors also argue that the process used to extract oil from larger fish is so sophisticated that contaminants don't end up in supplements.