Eating Fruits and Vegetables Helps Prevent Coronary Heart Disease

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The summary below is from the full report titled "The Effect of Fruit and Vegetable Intake on Risk for Coronary Heart Disease." It is in the 19 June 2001 issue of Annals of Internal Medicine (volume 134, pages 1106-1114). The authors are KJ Joshipura, FB Hu, JE Manson, MJ Stampfer, EB Rimm, FE Speizer, G Colditz, A Ascherio, B Rosner, D Spiegelman, and WC Willett.

What is the problem and what is known about it so far?

Blockage of the arteries that supply blood to the heart (coronary heart disease) still causes more deaths in the United States than any other condition. Treating high cholesterol, high blood pressure, and diabetes; not smoking; and exercising regularly are all known to help prevent coronary heart disease. Whether particular diets are effective in preventing coronary heart disease is controversial, however. Several studies have suggested that low-fat diets may be particularly helpful; others have suggested that diets high in fruits and vegetables are key. Many fruits and vegetables contain large amounts of fiber; potassium; flavonoids; and antioxidant vitamins, such as vitamin C and vitamin E. Large studies that follow participants for a long time are needed to see whether diets rich in such ingredients help protect against coronary heart disease.

Why did the researchers do this particular study?

To see whether high fruit and vegetable consumption reduces the risk for coronary heart disease.

Who was studied?

The study included 84,251 women and 42,148 men. All were or had been health care workers, such as nurses and doctors. Women were 34 to 59 and men 40 to 75 years old when they entered the study. Women were followed for 14 years and men for 8 years.

How was the study done?

Researchers used information from two large studies originally designed to monitor the general health of middle-aged and older women and men. Participants from both studies completed extensive questionnaires about their diets. Every 2 years, they answered questions about the occurrence of coronary heart disease and other medical conditions.

What did the researchers find?

People who ate many fruits and vegetables were older, generally had healthier living habits, and smoked less than people who ate few fruits and vegetables. They also had fewer heart attacks. Although the lower occurrence of heart attacks was partly explained by health factors other than diet, it was also independently related to high fruit and vegetable intake. Green leafy vegetables and fruits and vegetables rich in vitamin C were most protective against heart attacks.

What were the limitations of the study?

All participants in this study were health care workers; their intake of fruits and vegetables may not be the same as that in the general population. Responses on dietary questionnaires may not always accurately reflect actual intake of foods. Furthermore, the exact benefits of particular diets are very difficult to sort out when multiple factors, such as exercising and not smoking, may also be contributing to the benefits.

What are the implications of the study?

Diets rich in fruits and vegetables help prevent coronary heart disease. Green leafy vegetables and fruits and vegetables that have high amounts of vitamin C are particularly beneficial.