Was Grandma right about Cod Liver Oil

Some of us are old enough to remember when children had to swallow a daily spoonful of cod liver oil (usually against their will) as a vitamin supplement. In a recent small study at Cardiff University in Wales, people with severe osteoarthritis who took cod-liver-oil capsules for 12 weeks showed dramatic reductions in enzymes in the body that cause cartilage damage and joint pain. Thus, the researchers claimed to have proven that “Grandma was right” about the oil, and hailed it as an arthritis breakthrough and a way to reduce the rising demand for joint replacement operations. Are they right?

Osteoarthritis, the breakdown of the cartilage that cushions the joints, causes pain and stiffness in millions of people as they grow older. 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 re-duce symptoms. There is also an inflammatory element in osteoarthritis, but this is apparently the first study to look at fish oil’s effect on the disease in humans.

What’s the catch?

Here are some reasons to think twice before taking cod liver oil:
First of all, despite all the ballyhoo about the study, it has not yet been published, so it can’t be evaluated. Even if the results turn out to be solid, they would have to be confirmed by more research.

This short-term study looked only at biochemical markers for osteoarthritis (certain enzymes in cartilage). It did not involve X-rays to see if cartilage breakdown actually was reduced. It also did not evaluate whether the cod liver oil reduced symptoms.

Though fish oil is rich in heart-healthy omega-3s, supplements can pose dangers. They can increase the risk of hemorrhagic stroke, and people taking anticoagulants should not take them. Large doses may suppress the immune system. The American Heart Association does say that people with heart disease should consider taking the supplements, but only if they don’t eat enough fish and after consulting a doctor. Eating fish is a better option for most people.

Cod liver oil, bottled or in capsule form, has special problems. It is the richest source of vitamins A and D. Just one teaspoon has 4,500 IU of A, for instance, and the standard dose is one to three teaspoons a day. The capsules 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. Too much vitamin D can also be toxic.

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.

Words to the wise: If you have arthritis and want to see if fish oil helps, eat fatty fish two or three times a week. Even if it turns out that fish oil doesn’t help, there are other known benefits from eating fish. If you want to try the supplements, avoid cod liver oil—and talk to your doctor first.