Wednesday, 1 December 2010

Was your granny right - is fish good for your brain?

Regular research studies suggest that eating fish is good for you because it supplies a source of omega-3 essential fatty acids (EFAs), but you could be forgiven for wondering why there's so much fuss about them. Just how essential are they?

Very, is the short answer. Omega-3 EFAs are critical for our health, and the development and function of our brains in particular. We have to get them from our food, as we can't manufacture them ourselves.

Why do we need omega-3s?

While Western diets tend to provide excessive omega-6 fatty acids, many are relatively lacking in omega-3. This matters, because the ratio of omega-6 to omega-3 in our diets should be around 3:1 or less, but for most of us it's nearer 10:1 and in some cases as high as 20:1. Not only that, omega-6 competes with omega-3 for conversion to its respective EFAs, so a high intake of one can leave us deficient in the others.

"What's more, some people are more susceptible to a low ratio," says neuroscientist Dr Alex Richardson, a senior research fellow in physiology at Mansfield College, Oxford, and a member of the International Society for the Study of Fatty Acids and Lipids. "And some people may also have an in-built inefficiency in their conversion process, making them even more susceptible to deficiencies. Symptoms of low omega-3 status, which we know can affect neurotransmitters such as dopamine and serotonin in the brain, can include mental health problems ranging from depression, mood swings and anxiety to behavioural problems like ADHD, dyslexia and dyspraxia."

Could we get enough from our diets?

Cold-water fish like mackerel, herring, tuna, salmon and sardine are an excellent direct source of the omega-3s our brains need, and the current Food Standards Agency recommendation is that we eat four 140g portions of oily fish every week. But when was the last time you ate a herring? If we followed these guideline we would get enough omega-3, but it's not quite as simple as that. "Many things can contribute to low omega-3 status," says Dr Richardson. "One is our high intake of not only omega-6 but hydrogenated and trans fats, found in highly processed junk foods that are high in vegetable fats. These can block the conversion of omega-3s, as will a lack of any one of the co-factors necessary for conversion - vitamin B3 and B6, vitamin C, magnesium, and zinc, to name a few. Stress and some viral infections can inhibit conversion, while excessive drinking and smoking both help destroy these crucial fatty acids. So it's imperative that while upping your intake of omega-3, you cut out the junk."

Can EFAs help improve our mental health?

Dr Joseph Hibbeln, of the National Institutes of Health in the US, published research on fish oils and depression in The Lancet as long ago as 1998. He claims omega-3 deficiency may have an affect on mental health, and suggests that the increase in depression rates could be linked to our vastly increased use of vegetable oils, and the corresponding increase in omega-6 and depletion of omega-3. Other studies have shown that 1g of EPA (an omega-3 fatty acid) every day can be as effective as Prozac and Seroxat in tackling depression - without the side effects.

How much do we need?

The recommended therapeutic dose of EPA is 1g per day for those with mental health problems or 500mg for those without. That's 1g of EPA, not 1g of oil, something to consider if you're buying supplements. "Supplementation isn't necessarily a bad move, if you're improving your diet and cutting out processed foods," says Dr Richardson. "But only if you take a supplement that gives you what you need. Cod liver oil provides some omega-3, along with vitamins A and D, but this and ordinary fish oils can also contain a lot of saturated fat. And if you took enough to obtain 1g per day of EPA, you would risk vitamin-A toxicity. Livers detoxify, and as cod swim in some pretty polluted waters, it's worth checking that your supplement carries no risk of containing mercury, PCBs or other contaminants."

What's the vegetarian option?

"Flax seeds and flax oil provide the omega-3 fatty acid ALA, but this still needs conversion to EPA and DHA, another fatty acid, whereas fish oil doesn't," says Dr Richardson. "The body isn't good at making this conversion, because it's so dependent on numerous co-factors. Some knowledgeable vegetarians therefore choose an algal-source DHA supplement in addition to plenty of flax seeds or oil and green leafy vegetables that provide ALA."

What are the other benefits?

There is also some research-based evidence to suggest that omega-3 EFAs, which have an anti-inflammatory affect, also help protect against coronary heart disease, as well as Alzheimer's Disease and rheumatoid arthritis. There's even evidence to suggest that omega-3s can help with benign prostate disease. As far back as 1986, Dr David Horrobin published research in the Journal of the National Cancer Institute showing that exposing cancer cells to EFAs like EPA inhibited growth and could enhance the effects of chemotherapy. "Omega-3 EFAs are no miracle cure," says Dr Richardson. "But their benefits are increasingly relevant in our malnourished, stressful and ageing society. We ignore this at our peril."

So your Granny was right... fish is good for the brain.

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