Fruits and Vegetables  

Your mother was right: Fruits and vegetables are good for you. We've known for decades that fruits and vegetables contain important vitamins, minerals, and other nutrients. Science has more recently established that eating lots of fruits and vegetables can help prevent some life-threatening diseases.

The Healthy Eating Pyramid

Even more recently, researchers are coming to understand that the key to this advice is the phrase "fruits and vegetables." While a diet high in fruits and vegetables is healthful, that doesn't mean that taking pills and supplements that contain individual vitamins and minerals in megadoses will do the same thing. Out of hundreds of studies that have tried to separate individual components of foods and determine their specific health effects, only a tiny handful have produced convincing results. Many have fallen flat. Remember when everyone was taking vitamin E for everything from heart disease to memory loss? How about vitamin C to prevent colds? Or antioxidants to prevent cancer? Promising early evidence has failed to pan out for many of these links.

Fruits and vegetables contain hundreds of components known as phytochemicals, the majority of which have yet to be discovered. These phytochemicals appear in a vast number of combinations in the plants found in nature. In addition to phytochemicals, fruits and vegetables are a valuable source of fibre. Fibre serves many functions in the body. In particular, it keeps the digestive system running smoothly and may reduce the risk of heart disease and some gastrointestinal problems, and possibly some cancers. Finally, fruits and vegetables are high in beneficial minerals such as potassium, which lowers blood pressure.

Which combinations of which substances protect against which diseases? The answers are proving elusive. However, when it comes to food, such major studies as the Nurses' Health Study and the Health Professionals Follow-Up Study have shown that a diet rich in fruits and vegetables can help lower the risk of hypertension, heart disease, and stroke, and that people who follow such a diet live longer than those who don't. Studies also show that such a diet may reduce the risk of some forms of cancer — probably esophageal, stomach, and lung cancers, according to a review of hundreds of studies by the International Agency for Research on Cancer.

As if these benefits weren't enough, research also suggests that people who eat plenty of fruits and vegetables are less likely than others to develop two common age-related eye diseases — cataracts and macular degeneration — as well as diverticulitis, a painful intestinal condition. Such findings give fruits and vegetables a prominent place in the Healthy Eating Pyramid, which recommends eating fruit two to three times a day and eating vegetables "in abundance."

From the Harvard Health Publications Special Health Report, Healthy Eating: A Guide to the New Nutrition.