By GWYNETH REES

Last updated at 21:46 02 December 2007

Many claim to have found the answer to keeping the mind active, from crosswords and Sudoku to plenty of exercise and cold showers.

But now it seems the secret may lie in our lifestyle and what we eat to fuel our bodies.

Dark chocolate and plenty of cold meat for breakfast top the list for boosting grey matter, researchers suggest, while sex is essential for keeping the brain fit in later life.

Those wishing to improve their mental power should avoid smoking cannabis, watching soap operas and hanging out with those who moan.

But cuddling a baby, cheating at homework, reading out loud and doing a business degree at university are all good for an efficient mind.

The theories, based on research from experts around the world, are contained in the book Teach Yourself: Training Your Brain.

Author Terry Horne, a business lecturer at the University of Central Lancashire, said: "What we eat and drink, how we learn at school and what type of moods we have are all crucial.

"People can make lifestyle choices that will constantly increase our cognitive capacity throughout our adult lives."

The book contains mental exercises and radical thinking on how diet, the environment, stress and other aspects of modern life affect our mental capacity.

It claims sex has a positive impact, listing seven chemical reactions the brain undergoes during intercourse which improve its functioning ability.

For instance, raised levels of oxytocin - or the "trust" hormone - increase a person's readiness to think of novel or risky solutions to a problem. Elements in dark chocolate-also prove beneficial.

Magnesium and antioxidant chemicals increase the supply of oxygen to the brain and reduce the chances of brain damage through a stroke. Ditching a low-fat diet is also recommended to boost performance.

The book suggests a breakfast of eggs, fish or cold meat, a lunch of protein-based foods such as oily fish and dark green vegetables, and carbohydrates for dinner - but not caffeine, alcohol or red meat.

Children should not do homework on their own - minds function better when working with parents or classmates.

It also says that speaking in front of a class helps pupils because of the repetition involved. And adults can boost memory by counting aloud to 99 in threes as fast as they can.

The book recommends that readers should seek a concept known as BLISS - Body-based pleasure, Laughter, Involvement, Satisfaction and Sex - which all enable the mind to perform well.

Mr Horne added:

"Mix with people who make you laugh, have a good sense of humour or who share the same interests as you, and avoid people who whinge, whine and complain, as people who are negative will make you depressed."