Could fish make my child smart?
Mitchell Tonks has always been passionate about fish. He grew up by the sea and after a brief stint as an accountant, became a fish chef and founded a chain of fishmongers and restaurants. Like many of us, Mitch had heard about omega-3 and knew it was in some fish, but didn’t really know what it was. In Could fish make my children smart Horizon explores what omega-3 is, what it does and whether we really need it.
Omega-3 is a fatty acid, which is essential to our well being. One of the first people to realise its importance was an Oxford scientist, Hugh Sinclair. Back in the forties he realised that the Inuit ate vast amounts of fat yet hardly ever suffered from heart disease. He believed this was due to the protective effect of one fat, omega-3, found in oily fish. However, at the time this was such a controversial idea – that a fat could be good for us – that he was ridiculed and lost his post at the university. Undeterred, he continued to study omega-3 and put himself on an ‘Eskimo diet’ – for 100 days he ate nothing but seal blubber and fish. He found that he not only lost weight in spite of eating half a kilo of fat per day, but bled for increasingly long times when he cut himself. His blood had now become very thin. He thought that this might be how omega-3 worked – by preventing red blood cells from being sticky so that they did not clot and cause heart failure.
After two seminal studies, the Seven Countries Study and the GISSI study, which focused on heart disease, we now know that omega-3 does have a protective effect against cardiovascular disease. People who’ve had a heart attack and who took a gram of omega-3 a day were less likely to die suddenly of heart disease. Doctors think that omega-3 may have a protective effect against any cardiovascular disease: new research in this area will be published in autumn 2005.
Thirty years ago scientists realised the omega-3 is an essential component of the brain, including the visual system. Subsequently we have realised that omega-3 may help alleviate depression by boosting levels of omega-3 in the brain. Studies from America have correlated rates of depression with the amount of fish eaten – countries that eat less fish have high rates of depression.
A huge amount of research has now been carried out on omega-3 ranging from its effect on Alzheimer’s, Parkinson’s, autism, dyslexia, multiple sclerosis and even IQ. However, more research is needed before we can prove what omega-3 can or cannot do. In spite of this, we know that our diet used to be higher in omega-3 than it is now and so many think we should try and elevate levels of omega-3 through eating vegetarian sources, such as flaxseeds and walnuts, or by eating more oily fish.
Mitchell Tonks, naturally, believes we should be eating more fish! He’s designed some heart-healthy and mood-boosting recipes using fish – and one for vegetarians.
Omega-3 Q&A
What is omega-3?
Omega-3 is an essential fatty acid, which means that it is a fat vital to the functioning of the human body but cannot be manufactured by the body. It occurs in vegetarian form (in green leafy vegetables, walnuts and flaxseeds) as alpha-linolenic acid (ALA) and is then converted by enzymes to eicosapentaenoic acid (EPA), some of which is then converted to docosahexanoic acid (DHA). In the brain EPA acts as a signalling molecule, whereas DHA is part of the structural membrane brain cells.
What is the recommended amount?
There are no government guidelines on omega-3, but Professor Artemis Simopoulos from Washington University, who has studied omega-3 for many years, recommends a gram a day or seven grams a week. This requirement could be satisfied by eating two generous portions of salmon or other oily fish a week.
Fish that contain the highest amount of omega-3 (1-2 grams per 100g fish) are tuna, salmon, herring, anchovy, trout, mackerel and herring.
For vegetarians, Professor Simopoulos recommends having a tablespoon of flaxseed oil or one to tablespoons of ground flaxseeds a day (see What about vegetarians and vegans?).
Currently supplements are derived from purified fish oil; there are no vegetarian sources that combine EPA and DHA although they could be derived from marine algae in the future. Supplements containing only DHA from marine algae are available.
What about fish stocks?
Currently many of our fish stocks are overfished. 52% of fish stocks are fully exploited, which means that they are being fished at their maximum biological capacity. 24% are over exploited, depleted or recovering from depletion. 21% are moderately exploited. Only 3% of the world's fish stocks are underexploited. Yet human consumption of fish increased to 100.7 million tonnes in 2002, up from 93.6 million tonnes in 1998.
The Marine Stewardship Council run a certification scheme; any fisheries with their logo are running on sustainable lines. Information on which fish to buy, which ones to avoid can be found in a book by the MSC, The Good Fish Guuide, or at www.fishonline.org
What about vegetarians and vegans?
The conversion from the parent omega-3, ALA, to EPA and DHA is slow and inefficient. 5-10% of ALA converts to EPA and 2-5% of DHA. American guidelines for vegetarians indicates that adequate amounts for men is 17g of ALA and women should have 12g per day. Professor Simopoulos believes vegetarians should eat twice this amount.
However, most vegetarians and vegans have very low levels of saturated fats in their diet and are therefore the group at lowest risk of having heart disease in western populations. Moreover, Professor Tom Sanders, from Kings College London, has spent thirty years studying omega-3 in relation to vegetarians and vegans and found no health problems.
Practical guidelines to increase omega-3 are 1) to include a wide variety of plant foods, 2) get fat from whole foods such as seeds, olives, avocadoes and soya products, 3) use olive or canola (rape seed) oils to cook with and cold oils that are rich in omega-3 (walnut and flaxseed oils, for instance, are high in omega-3 but heating destroys the fatty acid), 4) limit intake of processed foods containing trans fats and omega-6, and 5) include foods rich in omega-3 (such as green leafy vegetables, nuts, seeds, especially flaxseeds and walnuts).
Will taking omega-3 make my children smart?
In studies on children with ADHD and dyslexia, omega-3 supplements helped 40 % of the children with their reading ability and concentration. The Middlesborough trial has just been completed, which studied 270 normal school children and found that forty per cent of those who had taken omega-3 supplements improved in their school work. However, as Professor Tom Sanders, of King’s College, London says, “We know that when people are being observed they change their behaviour and certainly when it gets the attraction of the media in the papers it will cause all sorts of biases in the results. I find it hard to believe that taking fish oil will suddenly transform a child’s reading ability.”
What is the problem with omega-6?
Omega-6 is another essential fatty acid, which is vital to the functioning of the human body. It is particularly important in the visual system. However, eating too much omega-6 can prevent the uptake of omega-3. Omega-6 starts off as linoleic acid (LA), which is the precursor to gamma-linoleic acid (AA) and arachidonic acid (AA). The enzymes used in the conversion process are the same enzymes that convert omega-3 ALA to EPA and DHA. Therefore eating too much omega-6 can prevent the uptake of EPA and DHA in the brain.
Over the last century there has been a thousandfold rise in oils containing omega-6 and now one in five of our calories comes from oils and fats rich in omega-6. The main reason is because the food industry has hydrogenated oils to create hard fats - margarines that are more stable and have a longer shelf-life. Since vegetable oils are cheap, this meant that omega-6-rich oils suddenly became much more readily available and widespread.
Cutting out hydrogenated fats, margarines, sunflower and safflower oils, processed and fried foods will help lower omega-6.