Have you noticed how much publicity “omega 3s” have been receiving lately? More and more manufacturers seem to be fortifying common foods with them and almost every day a new article appears about the benefits of consuming omega 3 supplements. Some seem to think them almost elixirs of life. Predictably this enthusiasm has been accompanied by a backlash from critics such as Ben Goldacre who argue that most of the publicity is just hype without significant evidence to back it up. Furthermore many of the enthusiasts are individuals who stand to gain enormously from sales stimulated by the hype. And some have turned out to be distinctly dodgy. Patrick Holford claimed that you could cure Aids with Vitamin C, a view endorsed by HIV denier Thabo Mbeki, former president of South Africa; sadly this misinformation may have contributed to thousands of unnecessary Aids deaths. Gillian McKeith, star of TV’s You Are What You Eat, plugged chlorophyll tablets claiming that they would oxygenate your blood, forgetting that it would be broken down by the gut and even if it worked there, there is not much light in the gut for photosynthesis to produce oxygen. Both were disciplined by the Advertising Standards Authority.
Still, the food supplement industry is worth nearly $30 billion per annum in the US. Much of it is based on miracle personal stories without the support of proper scientific studies such as randomised control trials. Nevertheless, among all the headline-grabbing stories that are easy to dismiss, there is probably a kernel of truth about the importance of omega 3s to our health; it would be a mistake to throw out altogether the baby of true effects with the bathwater of unsupported hype. Why do omega 3s deserve our attention?
In the 1920s George and Mildred Burr discovered that two long-chain unsaturated fatty acids, named alpha linolenic acid (ALA) and linoleic acid (LA), were essential in the diet because mammals cannot synthesise these molecules from simpler components. ALA and LA are found in seeds such as rape or flax; they consist of 18 carbon atoms in a long chain. They are called “unsaturated” because eight of the carbon atoms are joined by double bonds. ALA is called “omega 3” because the first of the four carbon double bonds is three carbons away from the methyl end of the molecule. LA is termed omega 6 because the first double bond is six carbons away from the methyl end. They are truly essential and you would die if you did not consume them.
However, these 18 carbon fatty acids are not the ones the body actually uses. A crucial constituent of our nerve and muscle membranes is a 22-carbon chain, docosahexanoic acid (DHA) that has six double bonds, while a 20-carbon omega 3 acid, eicosapentanoic acid (EPA), is the basis of many vital anti-inflammatory signalling molecules called eicosanoids. Many animals are good at elongating the seed-derived 18-carbon chains into these longer chains; but humans do this very inefficiently. Oily fish concentrate EPA and DHA which they gain from algae in the sea. Hence so long as we humans eat oily fish regularly, as we used to, we obtain most of the EPA and DHA that we need to keep body and brain healthy.
DHA is vitally important for constructing the membranes surrounding our nerves and muscles. Its precise length and charge profile is just right for enabling membranes to maintain the correct electrical charge across them and to allow rapid transfer of ions through the protein channels that pass through them. As a result each of our brains contains 100g of DHA. But we lose a few milligrams every day because it is also used, along with EPA, to make the eicosanoids. As a result DHA and EPA have to be continuously replaced from our diet.
So adequate intake of omega 3s from fish is vital for a large variety of functions. Their importance first became generally known when it was shown that those who eat the most oily fish have the lowest incidence of cardiovascular disease. People who eat two or more portions of oily fish a week have a five times lower risk of heart attacks or hardening of the arteries than those who eat none, partly because their heart membranes work better and partly because the eicosanoids combat the inflammation that is now known to make a powerful malign contribution to cardiovascular diseases.
Proper electrical functioning of membranes is even more important in the brain. There is evidence that mothers who eat oily fish during pregnancy and then breast feed produce infants who have significantly higher IQs than those who eat none. They also protect themselves from postnatal depression; if they do not eat fish they hand over too many of their omega 3s from their own brains to their child’s. Their blues stem from depressed activity of the prefrontal cortex because it is responsible for controlling our emotions and it is the most vulnerable part of the brain to lack of DHA. Later in life it seems that omega 3s may protect against many neuro-developmental and mental conditions such as dyslexia, ADHD, autism, depression and even violence. Later still, a lifetime of high consumption of oily fish probably protects from both cancers and dementia.
Nevertheless, the idea that omega 3s can deliver real health benefits is remarkably controversial. The “puritanical principle” is probably at work here; it seems too good to be true that such a simple food could have so many good effects. Yet until very recently a major part of our diet was fish. It was readily available and extremely cheap compared with meat. Some argue that the improved efficiency of conduction and transmission within the nervous system that DHA brought us is the main explanation for our superior brain power. But now meat is relatively cheap; fish is expensive and we eat far too little of it.
However, the main reason for scepticism is the difficulty of proving cause and effect. That smoking causes cancers took 50 years to be accepted. Hopefully the evidence will build up faster for the importance of omega 3s, because there are no powerful vested interests opposing their consumption. They are natural foods, so they cause little harm. We need to do everything we can to ensure that people’s brains work as well as they can, if we are to conquer the world’s myriad problems, such as climate change, population growth, water shortage and mental disorders, that threaten to overwhelm us.