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.
