That finding emerges from a study that had nearly 5,000 English and Scottish people give details of their diet between 1937 and 1939 and has followed nearly 90 percent of them ever since. The youngsters who ate the most fresh fruits had the lowest risk of dying of cancer in the decades that followed, says a report in the March issue of the Journal of Epidemiology and Community Health.
No similar association was found for vegetables in the diet, researchers at the University of Bristol and the British Medical Research Council say. One possibility is that the custom then was to boil them for up to a half hour, which removed healthy micronutrients, the researchers say. Today's cookbooks say most vegetables should be cooked for no more than 20 minutes, with five to 10 minutes in the pot advised for most. However, the researchers note that one previous British study found vegetable intake was not as closely associated with reduced cancer risk as fruit intake.
It is "quite a remarkable study," says Dr. Michael Thun, head of epidemiological research for the American Cancer Society, who is impressed by the researchers' ability to follow the participants for more than six decades. But with an epidemiologist's eye, he can pick out some of its weaknesses.
It's not definitive because it doesn't have information about risk factors other than diet, Thun says. It didn't look at individual diets, and it is "a relatively small study."
Nevertheless, Thun says, the report fits right in with the American Cancer Society's dietary guidelines, which say that people should eat "a variety of healthy foods with an emphasis on those from plant sources." At least five servings a day of fruits and vegetables are recommended.
The study did find that people who had a high calorie intake as children had a higher risk of cancer later in life, but that does not establish obesity as a risk factor, says Dr. Maria Maynard of the British Medical Research Council, a leader of the trial. "We did not look at the association between body size and cancer risk in this study," she says. While there was no association between intake of specific nutrients such as vitamin C, vitamin E, and beta-carotene and cancer risk, Maynard says, "our research does not support or refute the effect of supplements."
The mechanism by which good eating protects against cancer is not clear, Maynard says. However, she points to the conclusion of the journal report: "This study provides some support for dietary guidelines focusing on fruit consumption rather than on the intake of particular micronutrients." And, she adds, "we found no reason to reject the public health message that a diet rich in vegetables has a number of health benefits."
You can learn more about healthy eating by consulting the guidelines of the American Cancer Society. Learn more about feeding children more fruits and vegetables from the American Dietetic Association.