by Stella Mcintyre

Created on: April 28, 2009

It's not just an old wives tale. Fish boosts brain power. The reason is all down to the presence of Omega-3 fatty acids in oily fish.

Oily fish like salmon, mackerel, trout and sardines contain omega-3 fatty acids in boatloads. Omega-3 fats have been proven to improve brain functions on many levels and keep joints working properly. They can slow the progress of degenerative diseases such as senile dementia. The essential fatty acids in fish oil taken during the final trimester of pregnancy will help the development of a baby's brain. So their contributions to a healthier lifestyle are not disputed.

If oily fish, rich in omega-3 fats is good for us it stands to reason that we can't eat too much of it, right? Actually this assumption is not only wrong but can be potentially damaging to your health.

Most of the tuna and salmon we consume contain alarming and dangerous amounts of mercury. Where does all this mercury come from? We dump waste in the sea. Pesticides are washed from the land into rivers, waterways and oceans. And what do you think happens to it all?

Fish eat it. Small fish get eaten by bigger fish, which also swallow the stuff. Larger fish like salmon and tuna come along and do the same, ingesting waste that's stuffed with heavy metals, mercury among them. And it remains in their systems until we, in turn, eat them. But our bodies can't excrete heavy metals, and that's the problem.

We need to be very careful about sourcing oily fish to make sure the benefits outweigh the dangers.

Here are three ways you can work towards preventing a build-up of mercury in your system:

1. Limit your intake of tuna (or similar) to one tin per week.
2. If possible eat only wild Pacific salmon, or second-best wild Atlantic salmon. If you can't get hold of these, go for organic farmed salmon from your local fish farm.
3. Eat more sardines! The smaller the fish, the less mercury (and other toxins) they will have accumulated - and the less number of steps taken through the food chain before they get to us.

You may wonder why all this is important. Think about this for a moment: the term "mad hatters" comes from the 19th century milliners' practice of polishing top hats with mercury!

Will mercury make you mad? Maybe not: but it can cause serious health problems, including chronic fatigue, headaches, memory lapses, irritability and depression.

For an alternative, you might consider taking a supplement such as cod liver oil capsules.

Another thing you can do is look out for food items rich in Omega 3 fatty acids, such as certain brands of margarines/butters, and Brazil nuts.

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