By Richard Harkness
Knight Ridder Newspapers

Q: I’m 25 weeks pregnant and just started taking a fish oil (omega-3 fatty acids) supplement, which I purchased from my chiropractor. The product is quite costly. The label says it is filtered twice and contains no mercury, but warns that pregnant women should contact their doctor before using. Why is that?

A: Fish oil supplements contain the omega-3 fatty acids EPA and DHA, which appear to be heart-healthy and offer other benefits.

Mercury in fish oil supplements seems not to be a problem. An analysis of a number of fish oil products by an independent testing company (www.consumerlab.com) found no detectable levels of mercury in the products tested. Mercury appears to accumulate more in fish meat than in fish oils. The analysis also found that none of the products contained unsafe levels of polychlorinated biphenyls (PCBs).

In this way, fish oil supplements offer an advantage over dietary fish, which have been found to contain mercury and other contaminants. That’s why the EPA/FDA issues guidelines on the amounts of various types of fish thought to be safe for consumption during pregnancy and nursing (www.cfsan.fda.gov/~dms/ admehg3.html).

But there’s another concern about dietary supplement use during pregnancy. The OTC supplements market is only loosely regulated. You can’t always be sure you’re getting what’s promised on the label unless the product has been certified by an independent testing organization such as consumerlab.com, mentioned above.

The pregnancy warning on the product you mention seems to be a general one aimed at erring on the side of caution, since it cannot be said with certainty that fish oil supplements are safe during pregnancy.

Of note, the new prescription product Omacor, a concentrated form of the same omega-3 fatty acids present in fish oil supplements, carries pregnancy category C labeling.

There are five FDA pregnancy categories for prescription drugs based on progressive risk: A, B, C, D and X. Category A is the lowest risk, X the highest.

Here’s the category C wording for Omacor: “There are no adequate and well-controlled studies in pregnant women. It is not known if Omacor can cause fetal harm when administered to a pregnant woman. Omacor should not be used during pregnancy unless the potential benefit justifies the potential risk to the fetus.”

In studies of pregnant rats, omega-3 fatty acids have been found to harm the embryo at doses estimated to be several times the recommended human dose.

It should be said that Omacor contains substantially more omega-3 fatty acids per 1 gram capsule than typical fish oil supplements.

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