The brain only weighs about 3lbs or so - a fraction of overall body weight - but it uses up about 20 per cent of daily calorie intake. A brain-healthy diet is essential for keeping your memory and intellect sharp, improving concentration and boosting your mood.

Here are a few ways of keeping the brain healthy through good nutrition:

Boost concentration with Oily Fish

Keeping concentration levels high depends on keeping the messages flowing freely between brain cells. These cells need oxygen to fire up and send a message, and they get oxygen from blood sugar.

Therefore by simply ensuring an adequate and steady calorie intake throughout the day is the first step to keeping focused and alert.

These signals are sent from one cell to another by nerve fibers. To ensure the messages flow freely, these fibers have to be insulated by a sheath, which is made by a fatty substance called myelin.

Omega-3 oils (found mainly in oily fish, but also in walnuts, pumpkin and flax seeds) help to build and maintain myelin.

Lift mood with Protein-Rich Foods

Neurotransmitters are chemicals responsible for carrying electrical messages between brain cells, and they also play a key role in mood.

One of the key neurotransmitters is dopamine, the 'feel-good' messenger. Rising levels of dopamine give you enthusiasm, drive and pleasure. Falling levels are liked to a sense of emptiness, sadness, irritation and boredom.

Sugary and fatty foods cause a surge of dopamine. However, this surge is then followed by an equally sharp drop, so to keep your mood lifted all day, it is better to eat slow release, protein-rich foods which provide a steady flow of energy.

Another way of ensuring a steady production of dopamine - and a continued good mood - is to supply the brain with precursors. These are the molecules which it uses to manufacture dopamine.

One important precursor called phenylalanine is found in beets, edamame beans, almonds, eggs, meat and grains.

Another neurotransmitter, called serotonin, helps you to feel serene and content, whilst combating anxiety. A carbohydrate snack will raise serotonin levels quickly, but it will also make you sleepy, so again, it is better to keep the level steady.

To manufacture serotonin the brain needs tryptophan, a substance found mainly in eggs and meat.

Enhance memory with eggs

Our ability to remember things depends on getting brain cells to make new connections. They do this best when they are highly excited - that is why we tend to remember events which happen when we are feeling emotionally or intellectually stimulated.

There is one key messenger in the brain which keeps brain cells excited - acetylcholine.

In fact, drugs which mimic the effect of this chemical have been found to boost memory in people with Alzheimer's.

This key chemical is made from choline, which is found in eggs, liver and soybeans.

Vegetables such as cabbage, broccoli and cauliflower also seem to help memory. Researchers found people who eat these foods perform better on memory tests.

Control Cravings by Limiting Stimulants

When the body becomes anxious, it produces stress hormones called glucocorticoids. These trigger the brain to seek ways to relieve the stress. And that's where sugary, fatty foods come in.

Studies of rats with high levels of stress hormones found that they developed compulsive behaviors, such as loading themselves with sugary drinks and eating lard.

The short-term effect was to lower their stress hormones and help them relax. However, the effect of comfort eating was also making them fat.

Over a long period, repeated exposure to sugar alters the way the brain responds - the body needs more and more of it to get pleasure, so it has an addictive effect in the same way that drugs do.

The only way to prevent cravings is to avoid the substances that create them. Try to limits your intake of sugar, coffee and highly processed foods, and try other sorts of dopamine-boosting activities such as exercise or socializing.