Omega 3 can also be displaced from the brain by man-made “trans-fatty acids”, by-products of the hydrogenation process that allows the food industry to use cheap, solidified vegetable oils instead of expensive animal or dairy fats. Animal studies reveal that trans-fats can become incorporated into the brain’s structure and alter the profile of its neurotransmitters, its signalling system.

Youngsters are free to wander into any corner shop and buy snacks containing oils that have never been tested for their effects on the brain.

“Every time children eat crisps, biscuits or cakes they are filling themselves with what are, essentially, toxic fats,” says Dr Richardson.

“This has been admitted by the United States Food and Drug Administration and the UK’s Food Standards Agency. Both warn about it, but they are not shouting loudly.

“There are no health benefits and many health costs to these hydrogenated fats. Yet they are all the fats some children and adults are eating. They are replacing the essential fats that would make their brains and bodies work properly with ones that are clogging up the machinery.”

There is another problem. The brain is suffering not only from junk fats, but from an excess of another essential fatty acid called omega 6, found in vegetable oils, meat and dairy products. “A burger and milkshake will give you plenty of omega 6,” says Dr Richardson.

In hunter-gatherer times the ratio of omega 3 to 6 in the brain is believed to have been one to one. In the past 50 years or so the ratio has become one to 15 or 20 in favour of omega 6. This upsets the immune system. “That imbalance is going to tip everyone into this pro-inflammatory state most of the western world is walking around in. We are talking about problems of the immune system, which shapes the developing brain.”