Fish is seen as a vital element of a well rounded and balanced diet. Of course many vegetarians would dispute that for a number of reasons. Today I am just focusing on the mercury levels which exist in the fish destined for consumption by humans.
Fish has always had a good reputation as far as what it contributes to the diet. Fish is low in saturated fat and high in the things that really add value to human health such as protein and healthy fatty acids.
The research I found seems to support that the fish sold in Australia does not contain alarming levels of mercury. Having said that, the general advice is that excluding pregnant and children under the age of six years, the consumption of fish with high levels of mercury should be consumed no more than once a week, the portion size for adults per fortnight 150 grams and for children over six, 75grams.
Mercury can be expelled from the body over time. This is still disputed by some as there is a school of thought that mercury remains in your system forever. It appears to be that people can only exceed the safe levels of mercury consumption should they eat a great deal of fish containing mercury over a period of many months. Personally I would prefer to err on the side of caution. As I have said before, less is often more in many situations.
There are three forms of mercury which exist in our environment - organic, inorganic and metallic. Methylmercury is an organic form of mercury and is the most dangerous. This form of mercury when found in fish mainly comes from mercury in ocean sediment. Microorgnisms then transform them into methylmercury The fish absorb the methylmercury into their tissues via their gills as they swim and through their digestive tracts as they feed.
The concern for pregnant women is the consumption of methylmercury as it poses a threat to the baby whilst in the womb. This threat ceases once the baby is born. The levels of mercury in the mother’s milk are not high enough to be a risk to the infant.
Fish that contain higher levels of mercury include:
shark, ray, swordfish, barramundi, gemfish, orange roughy, ling, southern bluefin tuna.
Fish that contain lower levels of mercury include:
shellfish including prawns, lobsters and oysters,
salmon, and canned tuna. However as in any situation there are others things to consider before consuming these fish, and that is are they at part of the key groups which are at risk of being over fished?
It is important to note where the fish are sourced from as different countries have different levels of what is deemed safe mercury content. There is also the added consideration of what is fed to the fish should they be sourced from fish farms. You also need to consider possible contamination from pesticides - again standards differ.
The safest choices are blue mackerel, herring, John Dory, ocean trout, salmon, sardines, silver trevally, silver warehou, anchovy, blue-eyed cod, bream, flathead, garfish, mullet, snapper and whiting.
It is the same with anything else that you put into your body. You need to weigh up the benefits against the risks and make an informed decision. If you rule out a food source totally then you need to have a sensible and sustainable plan on how you will satisfy the nutritional contribution that this food source has previously contributed to your diet.
Mercury in excess is without question dangerous to the human body. Nutritional deficit is also dangerous so it is important to strike a balance. Personally I prefer the vegetarian way of eating, that has not always been the case but it is my reality at this particular time. I can make such a decision for all sorts of reasons but I owe it to my body to ensure that it remains in optimum health. The best way to achieve that is by being an informed consumer.