A Contrarian View of Fruits and Vegetables?
There's always one. Or in this case, maybe eight.
In an analysis of eight different breast cancer studies which documented patients' fruit and vegetable intake, Dr. Stephanie Smith-Warner of the Harvard School of Public Health and colleagues came to a surprising conclusion: High fruit and vegetable consumption during adulthood did not appear to have a statistically significant impact on reducing breast cancer risk.
Writing in The Journal of the American Medical Association, Smith-Warner's team reported on their analysis of more than 350,000 women included in the group of studies, 7,377 of whom developed invasive breast cancer.
They specifically focused on five food intake variables-fruit, fruit juice, total fruit, total vegetables, and combined total fruit and vegetables-and compared their consumption with the eventual incidence of breast cancer. They found that breast cancer risk was only 3% to 9% lower for those women who consumed the highest levels of these foods.
The researchers noted the considerable body of research that has touted the consumption of fruits and vegetables for minimizing the risk of breast and other cancers. But they suggested that many of those studies were based on patient recall, which is more subject to bias.
While fruits and vegetables may protect against other cancers, they acknowledged, a specific link to a reduction in breast cancer risk might not be warranted.
And yet there is an extraordinary body of research showing that a balanced diet with plenty of fruits and vegetables can minimize the risk of many diseases, including breast cancer.
For example, in a study published in the European Journal of Cancer, researchers from the European Institute of Oncology in Milan found that a high consumption of fruits and vegetables had at least a moderate protective effect on the risk of developing breast cancer.
A team led by Dr. S. Gandini analyzed 26 studies conducted between 1982 and 1997 to examine the link between breast cancer risk and a woman's dietary intake of fruit and vegetables. They found "a significant protective effect for breast cancer due to higher vegetable consumption, high intake of vitamin C and beta-carotene." They cautioned, however, that while a generally higher fruit intake "may have a possible protective effect," a statistical significance was not observed.
Another study, published in the journal Epidemiology by a different group of Italian researchers, compared 4,522 patients with breast, colon or rectal cancer to 5,155 healthy controls. They found that those who ate four servings of raw carrots a week were 20 percent less likely to develop breast cancer and 30 percent less likely to develop colon or rectal cancer.
In that study, participants who consumed the highest amount of all kinds of raw vegetables-about 12 servings a week-had a 15 percent reduction in breast-cancer risk, a 26 percent reduction in colon cancer risk, and a 16 percent reduction in rectal cancer risk.
Among the different types of fruit, only apples, pears and kiwis were associated with risk reductions of at least 5 percent for all three cancer types, they concluded.
In a study published in the journal Nature, Dr. Rui Hai Liu of Cornell University and colleagues pointed out that the many antioxidants contained in fresh apples-phenolic acids and flavonoids-seem to work in synergy to inhibit the proliferation of tumor cells.
The researchers used extracts from Red Delicious apples to treat colon cancer cells in vitro and found that "cell proliferation was inhibited in a dose-dependent manner after exposure to apple-extract concentrations above 20 mg/ml." They had similar success in tests with human liver tumor cells.
They found that colon cancer proliferation was inhibited 57 percent with extract containing apple skin, and 40 percent by extract not containing skin.
About one serving (100 g) of fresh apple provides antioxidant activity equal to that of 1,500 mg of vitamin C, Liu noted. Apples contain almost 100 phytochemicals, he added, which may explain their remarkable antioxidant punch.
Finally, an article published in The Journal of the American Medical Association evaluated dietary questionnaires completed by more than 42,000 women as part of the nationwide Breast Cancer Detection Demonstration Project.
Dr. Ashima Kant, Ph.D. of Queens College of the City University of New York and colleagues said their survey findings showed that women with diets high in fruits, vegetables, whole grains, low-fat dairy and lean meats had a 30% lower risk of "all-cause mortality." In other words, a good diet makes a difference.
"Our results provide evidence in support of the prevailing food-based dietary guidelines and suggest that diets complying with current dietary recommendations are indeed associated with improved health outcome," they concluded. "The potential public health implications of these findings are considerable."
SOURCES:
The Journal of the American Medical Association, February 14, 2001; 285:769-801
The Journal of the American Medical Association, April 26, 2001; 283:2109-2115
European Journal of Cancer, March 2000; 36:636-646
Epidemiology, 1998; 9:338-341
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