We all know that the food we eat gives our bodies the energy necessary to keep it alive and healthy. These days most of us are aware that we need to eat a well-balanced diet in order to keep our bodies in good working order. However, far fewer people know about the vital role that food plays in keeping our brain - and hence our mind - healthy and efficient. Although our brain makes up a mere 2% of our body weight, it uses 20% of the body's energy. Keeping our brain supplied with energy is the key to mental efficiency, and to do this we need to consider both what we eat and when we eat.

The quality of the food we eat can influence mental functions such as learning, memory, concentration and decision-making. Studies have shown that children who mainly eat fast food, such as hamburgers and other foods high in fat and sugar but low in vitamins and minerals, experience more problems with fatigue, forgetfulness and lack of concentration than children who have a better diet. The brain needs glucose, but, unlike our muscles, cannot store it, so a constant supply is necessary. Since glucose is a form of sugar, we might think that the best way to keep our brain healthy is to eat lots of sweet, sugary foods. In fact, the reverse is true. When we eat high-sugar food, the glucose level in our blood rapidly rises, then quickly falls, which decreases mental efficiency. Instead, it is better to eat foods rich in complex carbohydrates and fiber, such as brown bread, brown rice, potatoes, beans and apples, which ensure a slower, more stable glucose supply. We also need to consume adequate amounts of iron in order to keep mentally sharp, as iron helps carry vital oxygen to the brain. Eating foods high in protein can improve our attention and concentration, as can eating fish containing a lot of oil, such as tuna and salmon.

When we eat is almost as important as what we eat. Eating regularly is important, since this ensures that the 100 billion nerve cells in the adult brain remain active at all times. Indeed, some experts recommend eating six smaller meals throughout the day rather than the traditional breakfast, lunch and dinner. If you prefer to stick to the traditional three meals, here is some 1ldvice. From the point of view of mental efficiency, breakfast is probably the nest important meal of the day. Some 10-33 % of American and European children do not eat breakfast, and yet research studies have shown that school students who regularly eat breakfast have better memories, test scores and attendance rates than those who do not. The same applies to adults, so if you want to be able to think clearly, don't skip breakfast. At lunchtime, eating a high-protein lunch will help maintain attention and memory throughout the afternoon. If you want to eat something between meals, avoid snacks full of fat and sugar, and instead try fruit, nuts or yoghurt. In the evening, experts advise us to eat a light dinner at least three hours before going to bed.

What and when we drink is as important as what and when we eat. Drinking enough water and other liquids is essential for maintaining a healthy brain and hence a clear mind. Coffee and tea are well known for helping to improve concentration, which is why I, like most British students, drank a lot of coffee to help me study for long hours when I was at university. However, recent studies have shown that too much coffee (four cups or more a day) can actually weaken concentration. Unless you need to stay up all night to finish an essay or prepare for an exam, it is best to avoid coffee in the evening, since it can keep us awake. Instead, try a glass of warm milk and honey, which helps us get a good night's sleep, something as essential to mental efficiency as good food.

注
• glucose グルコース; ブドウ糖
• complex carbohydrates 複合炭水化物

• 11. These days fewer people are aware of food's influence on the-health of the body than those who know about the important role food plays in keeping our brain healthy.
• 12. The brain uses a much higher percentage of the body's energy supply than its size and weight might suggest.
• 13. According to research studies, children who eat too fast tend to experience more problems such as tiredness and poor concentration than children who eat more slowly.
• 14. Foods high in sugar quickly increase the glucose level in our blood, which is more efficient than the slower supply of glucose we get when we eat heavier foods such as brown bread, brown rice and potatoes.
• 15. Eating oil-rich fish and foods full of protein is good for our brain, as it can help us pay attention and focus more clearly.
• 16. Some experts suggest that we should eat six smaller meals in addition to our traditional three meals a day in order to ensure that our brain cells stay active.
• 17. Up to a third of American and European children are in danger of poorer achievement at school because they do not eat breakfast regularly.
• 18. Experts advise us against eating snacks between meals and suggest instead that we have a light dinner in the early evening.
• 19. The writer drank a lot of coffee while studying at university, thinking that it aided concentration, but recent research has shown that drinking too much may have the opposite effect.
• 20. Since getting a good night's sleep is as important for the brain as good food, it is better to drink warm milk and honey with your coffee in the evening.