The omega-3 fatty acids in fish are good for your heart. Find out why the heart-healthy benefits of eating fish usually outweigh any risks.
By Mayo Clinic Staff
If you're worried about heart disease, eating one to two servings of fish a week could reduce your risk of dying of a heart attack.
For many years, the American Heart Association has recommended that people eat fish rich in omega-3 fatty acids at least twice a week. Doctors have long believed that the unsaturated fats in fish, called omega-3 fatty acids, are the nutrients that reduce the risk of dying of heart disease. However, more-recent research suggests that other nutrients in fish or a combination of omega-3 fatty acids and other nutrients in fish may actually be responsible for the health benefits from fish.
Some people are concerned that mercury or other contaminants in fish may outweigh its heart-healthy benefits. However, when it comes to a healthier heart, the benefits of eating fish usually outweigh the possible risks of exposure to contaminants. Find out how to balance these concerns with adding a healthy amount of fish to your diet.
Fish contain unsaturated fatty acids, which, when substituted for saturated fatty acids such as those in meat, may lower your cholesterol. But the main beneficial nutrient appears to be omega-3 fatty acids in fatty fish.
Omega-3 fatty acids are a type of unsaturated fatty acid that may reduce inflammation throughout the body. Inflammation in the body can damage your blood vessels and lead to heart disease and strokes.
Omega-3 fatty acids may decrease triglycerides, lower blood pressure slightly, reduce blood clotting, decrease stroke and heart failure risk and reduce irregular heartbeats. Eating at least one to two servings a week of fish, particularly fish that's rich in omega-3 fatty acids, appears to reduce the risk of heart disease, particularly sudden cardiac death.
Fatty fish, such as salmon, lake trout, mackerel, herring, sardines and tuna, contain the most omega-3 fatty acids and therefore the most benefit, but many types of seafood contain small amounts of omega-3 fatty acids.
Some fish, such as tilapia and catfish, don't appear to be as heart healthy because they contain higher levels of unhealthy fatty acids. Keep in mind that any fish can be unhealthy depending on how it's prepared. For example, broiling or baking fish is a healthier option than is deep-frying.
Some researchers are also concerned about eating fish produced on farms as opposed to wild-caught fish. Researchers think antibiotics, pesticides and other chemicals used in raising farmed fish may cause harmful effects to people who eat the fish. However, some farmed fish — salmon, sea bass and trout — have higher levels of omega-3 fatty acids than their wild counterparts.
For adults, at least two servings of omega-3-rich fish a week are recommended. A serving size is 3.5 ounces (99 grams), or about the size of a deck of cards. Women who are pregnant or plan to become pregnant and young children should limit the amount of fish they eat because they're most susceptible to the potential effects of toxins in fish.
The risk of getting too much mercury or other contaminants from fish is generally outweighed by the health benefits that omega-3 fatty acids have. The main types of toxins in fish are mercury, dioxins and polychlorinated biphenyls (PCBs). The amount of toxins depends on the type of fish and where it's caught.
Mercury occurs naturally in small amounts in the environment. But industrial pollution can produce mercury that accumulates in lakes, rivers and oceans, which turns up in the food fish eat. When fish eat this food, mercury builds up in the bodies of the fish.
Large fish that are higher in the food chain — such as shark, tilefish, swordfish and king mackerel — tend to have higher levels of mercury than do smaller fish. Larger fish eat the smaller fish, gaining higher concentrations of the toxin. The longer a fish lives, the larger it grows and the more mercury it can collect.
Pay attention to the type of fish you eat, how much you eat and other information such as state advisories. Each state issues advisories regarding the safe amount of locally caught fish that can be consumed.
If you eat enough fish containing mercury, the toxin can accumulate in your body. For most adults, however, it's unlikely that mercury would cause any health concerns. But, mercury is particularly harmful to the development of the brain and nervous system of unborn children and young children.
Still, the Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) recommend that these groups limit the amount of fish they eat:
- Women who are pregnant or trying to become pregnant
- Breast-feeding mothers
- Young children
Pregnant women, breast-feeding mothers and children can still get the heart-healthy benefits of fish by eating fish that's typically low in mercury, such as salmon, and limiting the amount they eat to:
- No more than 12 ounces (340 grams) of fish in total a week
- No more than 6 ounces (170 grams) of canned tuna a week
- No amount of any fish that's typically high in mercury (shark, swordfish, king mackerel and tilefish)
Some recent studies have linked high levels of omega-3 fatty acids in the blood to an increased risk of prostate cancer. But, other studies have suggested that omega-3 fatty acids might prevent prostate cancer.
None of these studies were conclusive, so more research needs to be done. In the meantime, talk with your doctor about what this potential risk might mean to you.
Eating fish rich in omega-3 fatty acids and other nutrients appears to provide more heart-healthy benefits than does using supplements. Other nonfish food options that do contain some omega-3 fatty acids include flaxseed, flaxseed oil, walnuts, canola oil, soybeans and soybean oil. However, similar to supplements, the evidence of heart-healthy benefits from eating these foods isn't as strong as it is from eating fish.
July 20, 2016
- Fish 101. American Heart Association. http://www.heart.org/HEARTORG/HealthyLiving/HealthyEating/Fish-101_UCM_305986_Article.jsp#.V238SaLcBRo. Accessed June 24, 2016.
- Mozaffarian D. Fish oil and marine omega-3 fatty acids. http://www.uptodate.com/home. Accessed June 25, 2016.
- Sala-Vila A, et al. New insights into the role of nutrition in CVD prevention. Current Cardiology Reports. 2015;17:26.
- Zheng J, et al. Fish consumption and CHD mortality: An updated meta-analysis of seventeen cohort studies. Public Health Nutrition. 2011;15:725.
- Fish: What pregnant women and parents should know. U.S. Food and Drug Administration and Environmental Protection Agency. http://www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm393070.htm. Accessed June 24, 2016.
- Harris WS. You are what you eat applies to fish too. Journal of the American Dietetic Association. 2008;108:1131.
- Weaver KL, et al. The content of favorable and unfavorable polyunsaturated fatty acids found in commonly eaten fish. Journal of the American Dietetic Association. 2008;108:1178.
- Cabello FC, et al. Aquaculture as yet another environmental gateway to the development and globalisation of antimicrobial resistance. The Lancet Infectious Diseases. 2016;16:e127.
- Cole DW, et al. Aquaculture: Environmental, toxicological and health issues. International Journal of Hygiene and Environmental Health. 2009;212:369.
- Gil A, et al. Fish, a Mediterranean source of n-3 PUFA: Benefits do not justify limiting consumption. British Journal of Nutrition. 2015;115:s58.
- Oken E. Fish consumption and omega-3 long-chain polyunsaturated fatty acid supplementation during pregnancy. http://www.uptodate.com/home. Accessed June 25, 2016.
- Weylandt KH, et al. Omega-3 polyunsaturated fatty acids: The way forward in times of mixed evidence. BioMed Research International. 2015;2015:1.
- Brasky TM, et al. Plasma phospholipid fatty acids and prostate cancer risk in the SELECT trial. Journal of the National Cancer Institute. 2013;105:1132.
- Fu YQ, et al. Effect of individual omega-3 fatty acids on the risk of prostate cancer: A systematic review and dose-response meta-analysis of prospective cohort studies. Journal of Epidemiology. 2015;25:261.
- Sala-Vila A, et al. Dietary a-linolenic acid, marine x-3 fatty acids, and mortality in a population with high fish consumption: Findings from the PREvenci_on con DIeta MEDiterr_anea (PREDIMED) study. Journal of the American Heart Association. 2016;5:1.