Are You Eating Too Much Fish?

Eating fish, as part of a balanced diet, offers several nutritional benefits. But how do the mercury levels in fish impact your health? 

Fish does a body good. It’s a low-calorie protein source that contains several essential nutrients, including two types of omega-3 fatty acids that are beneficial for your heart and brain. But can too much of a good thing be harmful? 

“Fish is an amazing source of protein with key nutrients that we all need, and if anything we aren’t eating enough,” says Susan Carre, MD, a family medicine physician with Keck Medicine of USC. “Omega-3 fatty acids help with different mechanisms in our body that support bone health, cardiovascular health, weight management and more. We can benefit by eating fish to help support these different processes.” 

But there are some dangers to eating fish as well, she adds. “The most common danger of fish is the risk of choking on fish bones,” she says. “So, we do have to be mindful of the small bones whenever we are eating fish.” Another risk of eating fish is infections such as norovirus, which can cause nausea, diarrhea and/or vomiting. This sometimes happens when eating raw or undercooked fish. 

Can I get mercury poisoning from eating too much fish? 

“Mercury is an environmental chemical, and all of us have a little bit of it in our system,” Dr. Carre says. “The problem is that if we get too much mercury in our system, then it can have a toxic effect, and we can have symptoms such as poor muscular coordination and a tingly feeling in your hands and arms.” 

Americans eat an average of 16 pounds of fish and shellfish per year, according to a 2017 report from the National Oceanic and Atmospheric Administration (NOAA). Of that amount, 90% falls within the “best choices” for seafood, which includes fish that has low levels of mercury as defined by the Food and Drug Administration (FDA) and United States Environmental Protection Agency (EPA). Fish and shellfish in this category — such as salmon, catfish, tilapia, lobster and scallops — are safe to eat two to three times a week, or 8 to 12 ounces per week, according to the FDA. 

Halibut, grouper, mahi-mahi, albacore tuna and canned tuna fall under the FDA’s “good choices” category and should be eaten no more than once a week. Swordfish, orange roughy and bigeye tuna are best avoided, as they contain the highest levels of mercury. 

“There are several types of fish that have a higher risk, due to their size and how much other fish they eat. This includes shark, marlin, certain types of tuna, swordfish and whale,” Dr. Carre says. “But for the most part, there’s actually a really low risk for mercury toxicity from eating a reasonable portion of most other fish.” 

All fish contain some levels of mercury, even fish in the “best choices” category. High levels of mercury do not usually cause health issues for most people, except for young children and women who are pregnant, planning to become pregnant or nursing. High mercury levels can damage a developing fetus or cause damage to the nervous system in young children. Mercury can also stay in your body for up to a year, so if you’re planning on getting pregnant, you should follow the recommended amounts of fish consumption. If you’re not in an at-risk category and want to eat more than three servings of fish per week, stick to fish that are in the “best choices” category.  

But rest assured, a diet that incorporates lower-mercury fish is beneficial to your overall health, says Dr. Carre. 

“The American Heart Association also agrees that the benefits of eating fish outweigh the risk of potential mercury poisoning,” she says. “As long as we are sticking to two to three servings per week, it can put us at lower risk for cardiovascular events and improve our overall health.” 

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