Q. I eat a lot of fish for their omega-3 – should I worry about mercury?

Written by Catherine Saxelby on Monday, 24 March 2014.
Tagged: fats, healthy eating, omega-3

Q. I eat a lot of fish for their omega-3 – should I worry about mercury?
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Q. I have heard that there are high mercury levels in fish. Yet I also read that some fish are the best source of omega-3. I love eating salmon (both canned & fresh Atlantic) and canned tuna. I probably have about 5 serves a week. Do I need to be concerned about the mercury levels here in Australia?

A. This is really two questions in one. I'll start with the omega-3s. These unique polyunsaturated essential fatty acids can prevent stickiness of the blood, steady the heart's rhythm and lower blood pressure. Because our bodies only make small amount of them, we need to get them from the food we eat.

All types of fish have some omega-3, but the oily, cold water varieties like salmon have around double that of temperate water fish. Canned sardines, fresh Atlantic salmon, smoked salmon, canned mackerel, canned salmon and fresh tuna are all good sources. 

What about fish and mercury in Australia?

Mercury occurs naturally in the environment. It's all around us in air, water and food. Fish absorb it from water as it passes over their gills and from the food that they eat. Most fish have such low levels it's virtually undetectable. A few species of large predator fish or long-lived fish may have higher levels of mercury and that's why our food authorities have reviewed their guidelines on fish consumption.

For healthy adults and children, mercury from most fish is not a health risk when consumed as part of a normal diet. However, you should probably not eat fish with higher levels of mercury like shark (flake) more than once a week. It's a good idea to eat a variety of different fish species, but the salmon and canned tuna you like to eat have lower mercury levels and you can continue to enjoy them and get the benefit of those wonderful omega-3s.

It's a different story for pregnant women

Food Standards Australia and New Zealand recommends that women planning pregnancy and women who are breast feeding limit their intake of shark (flake), or billfish (broadbill, marlin and swordfish) to no more than one serving a fortnight with no other fish to be consumed during that fortnight.

For orange roughy and catfish, their advice is to consume no more than one serve per week, with no other fish being consumed during that week. The reason is that any mercury consumed may become concentrated in and affect the developing brains of both the unborn baby and the newborn.

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