Mercury in Fish

Consumption Advice: Making Informed Choices about Fish

Health Canada last issued consumption advice about mercury in fish in 2002. That advice is now being updated to better reflect the latest data on mercury levels in retail fish and the current consumption habits of Canadians, as well as to help Canadians make more informed decisions about the food they eat.

Most Canadians don't need to be concerned about mercury exposure as a result of fish consumption. In general, the types of fish that are most popular in Canada are also relatively low in mercury. However, there are some types of fish that, if eaten too frequently, could result in exposure to an unacceptable amount of mercury. The following advice will help to maximize the nutritional benefits of eating fish while minimizing the risk of exposure to mercury.

Canada's Food Guide recommends that Canadians eat at least two servings (of 75 grams each) of fish a week. Children, pregnant and breastfeeding women and women who may become pregnant can particularly benefit from the nutrients offered by fish. However, because the developing fetus and young children are also most at risk from mercury exposure, it's important that pregnant and breastfeeding women, women who may become pregnant and parents of young children are aware of what types of fish are a good choice for frequent consumption and which should be eaten less often.

Why Eat Fish and Which to Choose?

Most fish contain some of the long chain omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Recent evidence has suggested that fish consumption and the associated intake of EPA and DHA from fish can help maintain healthy heart function. Consumption of fish has also been associated with reduced risk of sudden cardiac death in healthy people and there is evidence that regular consumption of fish by pregnant women and women who may become pregnant plays a role in normal fetal brain and eye development.

Some types of fish have higher levels of these beneficial fatty acids than others. Fish and shellfish that contain higher levels of these fatty acids and are also low in mercury include: anchovy, capelin, char, hake, herring, Atlantic mackerel, mullet, pollock ( Boston bluefish), salmon, smelt, rainbow trout, lake whitefish, blue crab, shrimp, clam, mussel and oyster.

All fish are also a significant source of vitamin D and contribute valuable mineral nutrients to the diet such as selenium, iodine, magnesium, iron and copper.

Types of fish that should be eaten less often

Health Canada has identified certain fish as being of more concern when it comes to mercury in fish. Fish can accumulate mercury in their muscles through absorption from the surrounding water but mostly from the prey that they eat. This mercury can also concentrate up the food chain. Therefore, predatory fish that eat lots of other fish for food tend to contain higher levels of mercury.

These include fresh/frozen tuna, shark, swordfish, marlin, orange roughy and escolar (Note: Additional health information on escolar is available from Health Canada's Fact Sheet on escolar and CFIA's fact sheet.

Canadians who like to consume these types of fish can continue to do so, but should limit their consumption to the amounts shown in the table below. Other types of fish should be chosen to make up the rest of their recommended weekly fish consumption.

General Population - 150 g per week

Specified Women * - 150 g per month

Children 5-11 years old - 125 g per month

Children 1-4 years old - 75 g per month

* Specified women are those who are or may become pregnant or are breastfeeding.

150 grams represents two Food Guide servings and is equivalent to approximately one cup.

This advice does NOT apply to canned tuna. Information on canned tuna is provided in the next section.

Canned Tuna

Canned tuna, especially canned light tuna, is one of the most popular types of fish for many Canadians. The fish used in canned tuna products are generally younger and smaller and have significantly less mercury than fresh or frozen tuna, so that most Canadians don't need to be concerned about consuming canned tuna.

However, for those who consume large amounts of canned albacore tuna, there is some potential for exposure to higher levels of mercury than is considered acceptable.

Because of this, Health Canada has issued advice for children and some women on the consumption of canned albacore tuna. The advice does not apply to canned light tuna, nor does it apply to Canadians outside of the specified groups.

Canned albacore tuna is also often called canned white tuna, but it is not the same as canned light tuna. Canned light tuna contains other species of tuna such as skipjack, yellowfin, and tongol, which are relatively low in mercury. Canned light tuna also tends to be lower in cost relative to albacore tuna.

Canned Albacore (White) Tuna Advice (does not apply to canned light tuna)

Specified Women - 300 grams a week (4 Food Guide servings)

Children 5-11 years old - 150 grams a week (2 Food Guide servings)

Children 1-4 years old - 75 grams a week (1 Food Guide serving)

* Specified women are those who are or may become pregnant or are breastfeeding.

One Food Guide Serving is 75g, 2 ½ oz, 125 mL, or ½ cup and is equal to about half of a 170-g can (a very common can size).

In January 2007, Health Canada began an extensive survey of mercury levels in canned tuna in Canada. Once this new information is available, the advice related to canned albacore tuna may be further adjusted as required.

For More Information:

Health Canada's Mercury Information page.

Qs & As about mercury in fish

Health Canada's updated health risk assessment and risk management document.

It's Your Health on Mercury and Human Health.

Environment Canada - Mercury and the Environment, Fish Consumption

Nutrition for a Healthy Pregnancy (1999)

Canadian Food Inspection Agency - List of Canadian Acceptable Common Names for Fish and Seafood

You can also contact Health Canada's public enquires line for more information at (613) 957-2991 or 1 (866) 225-0709.