Eating fish is beneficial for health, say experts, because fish is a rich source of protein, omega-3 fatty acids, as well as a variety of vitamins and minerals. However, because of water pollution caused by chemical manufacturing, coal burning and other industries, fish often contains the metallic element mercury, in the form of methylmercury.
Excessive amounts of methylmercury can have a detrimental effect on your body, particularly the central nervous system. It is especially harmful for young children, breastfeeding babies and the developing foetus in pregnant women.
Some species of fish, notably the big predators, contain more mercury than others. Older fish are also likely to have higher levels of mercury than younger fish.
If you eat excessive amounts of fish high in mercury, the metal will accumulate in your bloodstream even though small amounts of it will be regularly eliminated through the body’s excretory system. It may take as long as a year for your mercury levels to drop after you stop eating fish.
While it is important for everyone to eat fish in moderation, the US Food and Drug Administration (FDA) advises pregnant women as well as breastfeeding women to limit their consumption to 12 oz (340 g) a week (two average meals) of a variety of fish and shellfish that are lower in mercury. It also advises all women who are of childbearing age (16-49 years) to adhere to this recommended number of servings. One serving of fish is 4 ounces (113.4g) for adults and 2 ounces (56.7g) for children aged 4-7 years.
The FDA has created a chart dividing fish species into ‘Best Choices’ for consumption, ‘Good Choices’ and ‘Choices to Avoid’.
Similarly, Singapore’s Health Promotion Board recommends breastfeeding mothers to avoid large fish like shark and swordfish.
5 fish that have low levels of mercury:
- Tuna (canned light)
- Trout (freshwater)
5 fish that have high levels of mercury:
- King mackerel
- Tuna (bigeye)