On Friday, I told you that it was better to eat a little fish every day than to eat a lot of fish just twice a week. The U.S. Department of Health and Human Services recommends that we eat at least eight ounces of fish or seafood every week. The American Heart Association recommends eating fish at least one to three times per week in order to get enough of the valuable omega-3 oils DHA and EPA. There is no doubt about the health benefits of fish.
But there's another side to fish and seafood. It contains mercury. I can't tell you how often patients ask me if fish is safe to eat based on the mercury issue. Now a new study offers some insight into the "should I or shouldn't I eat fish or seafood?" question. And the results are a bit surprising.
Researchers analyzed how often a group of 10,673 adults ate either fish or seafood. They found out that about 83% of them had eaten some form of seafood in the last 30 days. Of these, 40% had eaten seafood at least five times, 9% consumed only shellfish, 28% consumed only fish, and 43% of the total sample consumed both fish and shellfish. Then the researchers measured the participants' blood mercury levels.
Keep in mind that the EPA has decided that a mercury blood level greater than 5.8 µg/l is too high. Around 5% had blood mercury levels above the 5.8 µg/l cut-off. And here's the thing. Those people who ate the high mercury-containing fish, such as swordfish and king mackerel, were almost 500% more likely to have these high levels. Those who ate fish with lower mercury levels, such as tuna and salmon, were about 50% more likely to have the toxic levels. So there is a huge difference between the mercury effects of different fish.
Not surprisingly, the people who did not eat any fish or seafood had the lowest blood mercury concentrations of all, 0.45 µg/l. For those who regularly ate fish and/or shellfish, blood mercury levels increased according to how much they ate. People eating fish or seafood five or more times a month (that's almost half of the country) had the highest levels — 1.8 µg/l. And here's the surprising thing. Those eating either shrimp or crab did not have any more mercury than those who never ate any fish or seafood.
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So should you eat fish and seafood or not? Well, clearly shrimp and crab are in the no-brainer category. Eat them. So also are the high mercury fish such as mackerel, swordfish, shark, orange roughy, and tile fish. Don't eat them very often. I have never heard of tile fish, but you should know about them. Tile fish, also known as blanquillo have almost 70 times more mercury than the lower categories like salmon and cod. But some people ought to be especially careful.
These are the folks with chemical sensitivities or excessively bad allergies. That's because they are likely to be extra sensitive to the toxic effects of mercury. Also, children with autistic spectrum disorders are notoriously unable to handle mercury even in minute amounts. But what about the rest of us?
I personally like to keep my fish intake down to two to three times per month. Why? I don't like fish. But I don't have to be concerned about whether or not I get enough EPA and DHA in my diet. That's because I supplement with two capsules of Complete Daily Oils every day. That supplies more than enough of these essential fish oils. Also, don't forget grass-fed beef and other grass-fed meats contain EPA and DHA. There's one more recommendation I can make for the hardcore fish lovers.
DMSA is a naturally occurring sulfur compound that is an effective chelater of mercury. That means that it binds on to mercury and takes it out of the body. So it makes complete sense to carry some DMSA pills around and pop 200-300 mg when eating fish. It will bind up much, if not most, of the mercury in the DMSA and never get absorbed. You can buy DMSA online from several companies.
Yours for better health,
Frank Shallenberger, MD
Nielsen SJ, Kit BK, Aoki Y, et al. Seafood consumption and blood mercury concentrations in adults aged ≥ 20 y, 2007-2010. Am J Clin Nutr. 2014 May;99(5):1066-70.