Mercury is extremely toxic and abnormally high concentrations of mercury in the body can contribute to learning and attention disorders, slow intellectual development, and neurological conditions such as cerebral palsy. Although such levels are rare in adults, mercury can cause significant harm to neurological development of foetuses and children. For that reason, it is commonly advised for expecting mothers and young children to limit consumption of fish to no more than 12 ounces per week, and should avoid certain fish types altogether. However, advice for the general population is less well-known.

Fish consumption is the most common way people are exposed to mercury, but how does mercury contaminate fish in the first place? Mercury is released into the atmosphere from human activities such as burning fuel or natural sources such as volcanoes. Once mercury from the atmosphere is released into fresh waters and oceans, bacteria converts mercury into methylmercury, which is then absorbed by fish. Although these levels are initially low, they accumulate in fish over time as well as increasing up the food chain. This means that higher concentrations are found in older fish and predatory fish such as swordfish and sharks due to the effect of this build-up. Therefore, when we eat fish we then expose ourselves to these levels and consequently the potential health effects.

On the other hand, many of us are aware that fish consumption is beneficial, especially for its omega-3 content which is associated with lowering the risk of heart disease and Alzheimer’s to name a few. These benefits should not be overlooked by the mercury content of fish as we cannot completely eliminate mercury exposure, so we should rather look to minimise it. Most of us still don’t eat enough fish in our diet and it seems as though the recommendation of eating at least two portions of fish per week is beneficial to our health, as the benefits of fish consumption far outweigh the risks. However, we should look to better educate ourselves and become more aware of the fish we should chose to eat to maximise the benefits and cut the risks. Here are a few tips:

• Avoid excessive fish consumption
• Avoid eating more than one portion a week of fish that contains high mercury levels (e.g. shark, marlin and swordfish)
• Eat a variety of fish
• Consume fish high in omega-3 and low in mercury (e.g. salmon, sardines, and mackerel except king mackerel)
• Take fish oil supplements if you are not eating enough fish in your diet (fish oil supplements are mercury free)
• Pregnant women and children should completely avoid fish that are high in mercury levels (e.g. shark, marlin and swordfish) and limit consumption of fish to no more than 12 ounces per week

By eating smarter we can utilise the health benefits and reduce the risks when it comes to fish consumption.

Adie Blanchard – Researcher

References

Food.gov.uk. (2004). Food standards agency – mercury in fish. [online] Retrieved from: http://www.food.gov.uk/multimedia/faq/mercuryfish/#.UxBbDfl_u7I [Accessed: 28 Feb 2014].

Kris-Etherton, P. M., Harris, W. S., & Appel, L. J. (2003). Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Arteriosclerosis, thrombosis, and vascular biology, 23(2), e20-e30.

Shim, S. M., Dorworth, L. E., Lasrado, J. A., & Santerre, C. R. (2004). Mercury and fatty acids in canned tuna, salmon, and mackerel. Journal of food science, 69(9), C681-C684.

Shimshack, J. P., & Ward, M. B. (2010). Mercury advisories and household health trade-offs. Journal of health economics, 29(5), 674-685.

Shimshack, J. P., Ward, M. B., & Beatty, T. K. (2007). Mercury advisories: information, education, and fish consumption. Journal of Environmental Economics and Management, 53(2), 158-179.