The American Heart Association recommends that you eat two servings of non-fried fish twice a week to reduce your risk for congestive heart failure, heart attacks, strokes, and sudden death from heart disease (Circulation, May 17, 2018;138(1):e35–e47). A serving is 3.5 ounces of cooked fish or 3/4 cup of flaked fish.
Fish contain long chain omega-3 fatty acids, which help to protect your heart (Heart Lung Circ, 2015; 24:769–779). The fish with the highest levels of long chain omega-3 fatty acids include cold-water oily fish, such as salmon, herring, mackerel, tuna (bluefin and albacore), and sardines. Lower levels of omega-3 fatty acids are found in tilapia, catfish, flatfish, cod and sole, and in shellfish such as shrimp, lobster, crab, scallops, clams or oysters.
The omega-3 fatty acids in fish help prevent heart attack deaths by:
• reducing clotting (Atherosclerosis, 2008; 197:290–296)
• reducing plaques and stiff arteries (Atherosclerosis, 2007; 195:e190–e194)
• lowering triglycerides (J Am Coll Cardiol, 2011; 58:2047–2067)
• raising the good HDL cholesterol (J Clin Lipidol, 2014; 8:126–133)
Restrict Fried Fish
Eating a lot of fried foods is associated with increased risk for heart attacks (Clinical Nutrition, July 5, 2019), and in one study, eating fried fish or shellfish once a week was associated with a seven percent greater risk of death (BMJ, Jan 23, 2019;364:k5420). When you cook with water, the temperature cannot rise above the boiling point (212 degrees F), and the sugars in foods combine with the water to form end products that have not been shown to be harmful (J Am Diet Assoc, Jun 2010;110(6):911-16). However, when sugars or carbohydrates (chains of sugars) are cooked with proteins or fats at high temperatures and without water, the sugars bind to the proteins and DNA to form chemicals called Advanced Glycation Endproducts (AGEs). Browning during cooking is a sign that AGEs are being formed. AGEs turn on your immune system to cause inflammation (J Am Diet Assoc, Jun 2010;110(6):911–16.e12), that prevents your cells from responding to insulin, which can lead to diabetes or make it harder to control existing diabetes (Diabetes Care, January 2014;37:88-95). Many animal studies have shown that a diet high in AGEs prevents cells from responding to insulin, raises blood sugar levels and raises insulin levels, which can cause or worsen diabetes. AGEs also increase risk for heart attacks and cancers (Cancer Causes & Control, 2012, 23:405-420).
Other Concerns about Seafood
There is no strong evidence that eating fish more often than twice a week offers health benefits greater than those offered by eating fish twice a week. There is some concern that fish may contain mercury and other heavy metals that in large amounts may damage the brains of growing children (Neurotoxicol Teratol, 2016; 57:71–78). Fish spend their entire lives accumulating heavy metals in their bodies, so the highest amounts of heavy metals are found in the largest and longest-living predatory fish, such as shark, swordfish, tilefish, king mackerel, bigeye tuna, marlin, and orange roughie. The American Heart Association did not find that mercury in fish had any adverse effects on heart disease in adults (Circulation, May 17, 2018;138(1):e35–e47), but pregnant women and young children should restrict eating the largest and longest-living fish. Fish with low levels of mercury include mackerel, sardines, salmon, trout, herring, anchovies, Alaska pollock and haddock.
If you eat a lot of fish or shellfish from a local lake, bay or river, the U.S. Environmental Protection Agency (EPA) recommends that you check for pollution advisories in your area. It is also possible to get parasites or bacteria from uncooked fish or shellfish, so I suggest that you eat only cooked fish. This recommendation is hard for sushi lovers, but there are many delicious varieties of sushi that are made with cooked seafood (California rolls, shrimp rolls and so forth).
• Eat seafood two or three times a week, preferably fish that are high in omega-3 fatty acids and low in mercury, such as mackerel, sardines, salmon and trout.
• Use water-based cooking methods whenever possible: steaming, simmering, blanching, boiling, baking in a covered dish, and so forth. Avoid or limit deep frying and other cooking methods that brown or blacken the fish, which are signs of AGEs that can increase cancer risk.
• Include seafood as part of a high-plant diet with a wide variety of vegetables, whole grains, beans, nuts and other seeds. See my report on Anti-Inflammatory Foods.
• How about just taking fish oil pills? See Fish Oil Pills Have Not Been Shown to Prevent Heart Attacks