A Fishy Focus
I always try and select fish with three things in mind – health benefits, the health risks and the sustainability of the particular species. I don’t know about you but the mixed messages from the media and literature out there about fish have the potential to leave you tearing your hair out or just not caring what species you choose at the shops.
Although what you hear about fisheries and nutrition can leave you confused some things are clear. Fish is a good source of protein – compared to other sources such as meat and eggs it contains low levels of saturated fat (the bad stuff) and is a good source of selenium and long chain Omega-3 fatty acids (the good stuff).
The Good Stuff
Selenium is a non-metal micronutrient – that is it is a nutrient essential for cell function and production of hormones from the thyroid gland, but we only need small amounts. Although it is also an important antioxidant, selenium is toxic in large doses, but this is very unlikely as selenium is a rare element. One more important thing about selenium is it reduced the symptoms of mercury toxicity.
Long chain Omega-3 fatty acids; there are three kinds important to you for brain and eye function, one in particular for pregnant females. Their abbreviations are ALA, DHA and EPA and this is how you’ll hear people talking about them as their names are far too long. ALA is the version your body can’t produce, and uses to convert to DHA (the one essential to foetal brain development) and EPA.
These good fats have also been associated with lowering blood pressure and cholesterol, prevention of heart disease, slowing of Alzheimer’s disease, prevention of depression and prevention of behavioural disorders such as ADHD in children.
Marine algae produce these long chain Omega-3 fatty acids and as marine creatures eat these algae and then other marine creatures eat the ones that ate the algae the Omega-3’s accumulate. While we have a reduced reliance on Omega-3 due to our terrestrial environments not havening much Omega-3, marine organisms have not evolved the use of other nutrients such as Vitamin C and therefore contain much more. This means oily fish higher up in the food chain contain the most Omega-3.
The Bad Stuff
I mentioned saturated fats, but when it comes to fish you don’t have to worry about this. Unfortunately, long chain Omega-3 fatty acids are not the only thing fish accumulate in the food chain. They also accumulate Methylmercury and polychlorinated biphenyls (PCB’s) or essentially mercury (a heavy metal) and persistent organic pollutants. Algae absorb these toxins and then they accumulate up the food chain or otherwise know as trophic levels.
Mercury is a by-product from coal-burning power plants and chlorine production and has found its way into the marine food chain, accumulating in long lived fish and those higher up in the food chain. Mercury affects the brain, kidney and lungs and is particularly devastating to developing foetuses.
There are websites that help you work out an estimate of the amount of mercury in the fish you plan to eat such as www.gotmercury.org
PCB’s are no longer in production but are carcinogens (cancer causing) and accumulate in the environment in much the same way as mercury and Omega-3.
So eating fish is safer than not eating fish, but which fish do I choose?
It’s better to each fish lower in the food chain (that are often more sustainable) as they contain less mercury and choose fish higher in the food chain that have higher levels of selenium compared to mercury (which you’ll be glad to know is the case for most), which can be found on information sheets such as this one:
As far as sustainability – that depends on the method of fishing, that amount fished of that species and some important biological features of the species such as how much it reproduces and at what age it starts reproducing. Selecting a fish is easy with websites such as http://goodfishbadfish.com.au/ where you can enter the species of fish in a recipe you have selected to the website which will tell you if it is a sustainable choice or suggest similar more sustainable fish. This website also has recipes for less common more sustainable fish that you may not have encountered before.
Thank-you if you have read this far; the science of nutrition and fisheries are both very complex issues, that can be hard to communicate – so I hope I’ve helped you work some of it out!
Brunner, E.J. Jones, P.J. Friel, S. and Bartley, M. 2009, ‘Fish, human health and marine ecosystem health: policies in collision’, International Journal of Epidemiology, 38, 93–100.
Lando, A.M. Fein, S.B. and Choini, C.J. 2012, ‘Awareness of methylmercury in fish and fish consumption among pregnant and postpartum women and women of child bearing age in the United States’, Environmental Research, 116, 85–92.