Sometimes people want to know what type of food is healthy， and what kind of food may hurt our health.The United States Department of Agriculture has prepared a small book to help people learn about which types of foods are the healthiest to eat.The book describes six basic food groups： meat， dairy products things made from milk， grains， fruits and vegetables.The last group is fat， oil and sweets.

　　As a result of years of research， we know that too much fat is bad for our health.For example， Americans eat a lot of meat and only a small amount of grains， fruits and vegetables.Because of this， they often get cancer and heart disease.In Japan， on the other hand， people eat large amounts of grains and very little meat.They have a very low rate of cancer and heart disease.In fact， the Japanese live longer than people in any other country.Unfortunately， when Japanese people move to the United States， the rate of heart disease and cancer increases as their diet changes.What's more， as hamburgers and other high­fat foods become common in Japan， the rate of heart disease and cancer is increasing there as well.People are also eating more meat and dairy products in other countries such as Cuba and Hungary.It's no surprise that the disease rate in these countries is increasing along with the change in diet.Therefore， doctors everywhere advise people to eat more grains， fruits and vegetables， and eat less meat and dairy products.