Cod Liver Oil

Once used mainly as a vitamin supplement for children, cod liver oil is more likely now to be promoted for older people suffering from severe osteoarthritis, which is the breakdown of the cartilage that cushions the joints. Fish oil, rich in omega-3 fats, helps counter inflammation, so some people with another form of arthritis, rheumatoid arthritis (an inflammatory disease), take fish oil supplements to help reduce symptoms. There is also an inflammatory element in osteoarthritis, it is now known, and thus some people think that fish oil, specifically cod liver oil, might be useful.

Claims, purported benefits: Treats or cures arthritis. Fights cancer, prevents Alzheimer’s disease, depression.

Bottom line: No solid research has ever shown that cod liver oil prevents cancer, Alzheimer’s, or depression, but there is some evidence that fish oil, including cod liver oil, can ease the pain of arthritis and improve joint stiffness. But fish oil supplements can pose dangers. They can increase the risk of hemorrhagic stroke, and people taking anticoagulants should not take them.

Cod liver oil, bottled or in capsule form, has its own special problems. It is the richest source of vitamins A and D. Just one teaspoon of cod liver oil has 4,500 IU of A, for instance, and the standard dose is one to three teaspoons a day. Capsules of cod liver oil contain less oil, but the vitamin can still add up, especially on top of the amount you get from foods and from a multivitamin, if you take one. Recent studies have found that as little as 6,000 IU of vitamin A daily can interfere with bone growth and promote fractures. And women of childbearing age should not exceed 10,000 IU of vitamin A because of the risk of birth defects. Cod liver oil is made from livers, of course. The liver is a filter, so toxins (such as PCBs) get concentrated there. Thus cod liver oil is more likely to be contaminated than other fish-oil supplements.

If you want to try fish oil supplements, avoid cod liver oil—and talk to your doctor first.