Fish, Mercury, and Your Health
Fish and shellfish are an important part of healthy eating. They contain protein, vitamin D, vitamin B12 and omega-3 fats. Eating fish benefits heart health and it helps children’s brains and eyes to grow and develop. However, the fetus and infants exposed to high levels of mercury may have problems with learning, walking, and talking. It is important to choose fish that are low in mercury. Toronto Public Health’s Guide to Eating Fish for Women, Children and Families provides clear advice about choosing and eating fish.
Health Benefits of Eating Fish
Fresh, canned, and frozen fish and shellfish are high in protein, vitamin D and omega-3 fats. Two important omega-3 fats found in fish are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). EPA and DHA have been linked to improved heart health in adults. DHA supports brain growth and development in babies and young children.
Pregnant or breastfeeding women, or women who could become pregnant, should eat fish to get DHA.
Mercury and Health Risks
Mercury is a toxin that is harmful to our bodies. Here is an extended list to help you to be carefully choose fish that are lowest in mercury and best for the environment.
Fish may contain mercury. Large fish that live a long time and eat other fish contain the most mercury, which builds up in the tissue of the fish. When we eat these fish, the mercury builds up in our bodies.
Mercury gets into fish habitat when industrial air emissions settle into lakes and streams. As well, some products (such as old thermometers and car switches) leach mercury into the waterways from landfill sites. When fish eat the plant and aquatic life contaminated with mercury, it builds up in their tissue. Large fish that live a long time have the most mercury in their tissues because it builds up over time when they eat the smaller fish.
Mercury Content in Fish
There are different types of canned tuna. Read the label and choose “light” tuna because it is low in mercury. Choose “white” or Albacore tuna less often.
Salmon is a fish that provides a lot of omega-3 fats and is low in mercury. However, there are some concerns:
- low levels of other pollutants, such as PCBs, found in the fat of farmed salmon
- transfer of disease and parasites from farmed to local wild salmon
- pollution and waste from salmon farms
- stress on fish stocks used to feed farmed salmon
Wild salmon is lower in PCBs and has fewer ecological concerns than farmed salmon. Most canned salmon is wild. To lower the amount of pollutants in salmon, remove the fat and skin before cooking. Grill, broil or barbecue your fish so that the extra fat can drip off.
Sport fish are fish caught in local lakes and rivers. Some of these fish may not be safe to eat. If you eat sport fish, check the Guide to Eating Ontario Sport Fish or phone 1-800-820-2716 to get a free copy.
See the full list of fish species for more information.
Eating Fish Safely
Health Canada recommends eating at least two Canada’s Food Guide servings of fish each week that are high in omega-3 fats and low in mercury. Canada’s Food Guide defines one serving of fish as 75 grams or 2.5 ounces or about half a cup.
See Eating Well with Canada’s Food Guide for more information.
Women and Children
If you are pregnant or breastfeeding, or could become pregnant, you can still enjoy the benefits of eating fish if you choose carefully and eat a variety of fish. You can also give fish to your children as long as you avoid or rarely feed them fish that high in mercury. Mercury can cross the placenta and affect fetal brain and nervous system development. Studies show that children of women exposed to high levels of mercury during pregnancy have lower intelligence scores, delayed verbal and motor skills, impaired hearing and poor coordination.
Omega-3 Fish Oil Supplements for Pregnant Women
If you choose to take supplements, read the label carefully. Look for those that say they have been tested for contaminants. You may also look for omega-3 supplements that are made from marine plant sources. Fish liver oil contains high levels of Vitamin A which may cause birth defects.
Toronto Public Health supports food production that is sustainable. Poor fisheries management can result in habitat damage, threats to other aquatic life and overfishing.
For more information on making the best environmental fish choices refer to Guide to Eating Fish for Women, Children and Families.
Guide to Buying and Eating Fish
Some types of fish and shellfish contain mercury. Mercury is a toxin that is harmful to our bodies. Mercury exposure is especially harmful during fetal and childhood development because it can affect the brain and nervous system. Carefully choose fish that are low in mercury. Toronto Public Health’s “Guide to Eating Fish for Women, Children and Families” provides clear advice about eating fish for:
- women who could become pregnant
- teenage girls
- pregnant women
- breastfeeding women
Learn which fish are highest in omega-3 fats, lowest in mercury and how often you can eat them. Also, learn which fish are the best choice for the environment.
Download this wallet-sized guide to help you choose fish when you go shopping.
Guide to Buying Fish For Women, Children and Families
Also available in French.