Fish is the nutrition world’s double-edged sword-good one day and bad the next, according to experts. Sans mercury, I think most would agree that it is the perfect health food. Unfortunately, many types of fish (e.g., swordfish, shark, marlin and frozen or fresh tuna) contain high levels of this toxic metal, which can wreak havoc on the nervous systems of adults, children and developing fetuses.

Mercury accumulates in the atmosphere largely as a result of industrial pollution, which rains down on our oceans and soil, leading to widespread contamination, especially in fish-and the bigger the fish, the bigger the problem. According to the CDC, prolonged exposure to high levels of metallic, inorganic or organic mercury can permanently damage the brain, kidneys and developing fetuses.

But studies also indicate that the omega 3s found in fish offer the promise of higher IQs, in addition to loads of other health benefits such as preventing heart disease. So unlike any other food or dietary substance, consumers are put in the unusual position of weighing the risks and benefits of fish consumption, an issue long debated between public health and scientific authorities, especially as it pertains to pregnant women and young children.

Last September, the American Journal of Clinical Nutrition published a study noting that while Federal advisory boards have previously recommended that pregnant women limit their fish intake to two or fewer weekly servings of fish, data show the benefits of prenatal intake for child development may outweigh the risks.

In terms of heart benefits, just last month two studies discussing the importance of nutrients in preventing heart disease were published in high profile journals. The only food or dietary substance mentioned in both studies was fish (and their omega 3 fatty acid components). The Loma Linda University research published in the American Journal of Clinical Nutrition compared the effects of walnuts and fatty fish, demonstrating that in healthy individuals, walnuts lower cholesterol, while fatty fish lower triglycerides. Both, the authors said, have the potential to reduce the overall risk of coronary heart disease.

In the other study, which appeared in the Archives of Internal Medicine, researchers reviewed previously published studies and found that vegetable and nut intake and a Mediterranean dietary pattern appear to be associated with a lower risk for heart disease. In addition, modest relationships were found supporting a causal relationship between intake of several other foods and vitamins and heart disease risk, including fish and omega 3 fatty acids from marine sources.

According to a recent survey carried out by ConsumerLab.com, fish oils are now nearly as popular as multivitamins. In fact, almost as many consumers of multivitamins (74%) also take fish oil (72%), followed by calcium (55%) and CoQ10 (51%). Interestingly, among people using 10 or more supplements each day, use of fish oil (85%) exceeded that of multivitamins (76%).

The fish consumption conundrum is a perfect example of how the health of the environment impacts the health of people. Clearly, avoiding fish or fish oils is not the solution, nor are the warnings encouraging moderation. Instead, a clean environment would give authorities a clean conscience when it comes to recommending these highly beneficial substances.