More than 3.5 billion people depend on the ocean for their primary source of food. Fish is a valuable component of the human diet because it is easily digestible and contains high-quality protein that provides a mix of essential amino acids that our bodies cannot make themselves and must be supplied through our food.
Globally, seafood provides more protein than cattle, sheep, or poultry. Fish also contain a wide variety of vitamins and minerals including vitamins A and D, phosphorus, magnesium, and selenium. Research shows that omega-3 fatty acids, found abundantly in seafood, have health benefits, such as improved infant brain development and protection against heart disease and stroke. Most adults in the US consume much less omega-3 fatty acids than nutritionists recommend.
However, global fisheries face serious threats. Current research estimates that most commercial marine fisheries are being fished unsustainably and a recent study predicts that virtually all commercial species will not be viable by 2030 if we continue with current methods.
At the same time, fish may be contaminated by environmental pollutants, most notably methylmercury. Coal fired power plants are the most significant source of mercury that enters the ocean. Methylmercury is toxic to the nervous system, especially the developing brain. Because of the health risks for babies associated with methylmercury exposure, the United States Food and Drug Administration and Environmental Protection Agency have recommended that women of childbearing age, pregnant women, and breastfeeding mothers limit their intake of fish, and avoid all consumption of some types of fish higher in mercury (shark, swordfish, king mackerel, or tile fish). About 10% of all US women of childbearing age, and a higher percent of women who are older, Asian, or live near the coasts, have mercury levels above recommended limits. Current federal guidelines do not recommend a specific mercury limit for non-pregnant adults, but some evidence also suggests that mercury can increase risks for heart disease and neurological problems in adulthood.
Consumers can make healthy and sustainable food choices by choosing fish that is sourced sustainably and low in mercury. For specific recommendations, see the seafood decision guide in our resources.
Text provided by Emily Oken, MD, MPH, Associate Professor, Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute
Photo of Pike Place Fish Market courtesy of Monica's Dad | Flickr.com