More Fruit and Vegetables No Better for Breast Cancer Survival

July 17, 2007

SAN DIEGO -- A diet heavy on fruit and vegetables may not help breast cancer survivors reduce their risk of recurrence or death, researchers found.

SAN DIEGO, July 17 -- A diet heavy on fruit and vegetables may not help breast cancer survivors reduce their risk of recurrence or death, researchers found.

Breast cancer survivors who ate substantially more than the recommended five servings a day did not have lower risk of recurrence or new primary breast cancer (P=0.63) or lower risk of overall mortality (P=0.43) than those who ate only the recommended amount, according to the results of a randomized, controlled trial published in the July 18 issue of the Journal of the American Medical Association.

The high fruit and vegetable diet also showed no benefit among women who stood to gain the most-those with a baseline diet low in fruits and vegetables or high in fat, reported John P. Pierce, Ph.D., of the University of California in San Diego, and colleagues.

These negative findings from the Women's Healthy Eating and Living (WHEL) trial contrast with the modest benefit seen for a low-fat diet in the Women's Intervention Nutrition Study (WINS). (See SABCS: Low-Fat Diet Helps Prevent Breast Cancer Relapse)

These studies, added to inconsistent findings from observational studies, leave women with no clear dietary path to follow after breast cancer, said Susan M. Gapstur, Ph.D., and Seema Khan, M.D., both of Northwestern University in Chicago, in an accompanying editorial.

The multicenter WHEL trial included 3,088 women ages 18 to 70 at diagnosis and treated for early stage breast cancer within the preceding four years.

The women were randomized to an daily intervention diet of five vegetable servings plus 16 ounces of vegetable juice, three fruit servings, 30 g of fiber, and 15% to 20% of energy intake from fat or to the "Five-A-Day" diet (five vegetable and fruit servings, more than 20 g of fiber, and less than 30% of daily calories from fat) recommended by the Department of Agriculture and National Cancer Institute.

The intervention group received telephone counseling and newsletters about the diet and could attend 12 cooking classes. The control group received print materials describing the "Five-A-Day" dietary guidelines and could attend four cooking classes.

At baseline, 24-hour dietary recalls revealed both groups averaged more than seven servings of vegetables and fruit with no significant differences in diet between groups.

The control group showed only modest changes in diet over the follow-up period although energy intake from fat increased 13%.

The intervention group at one year had raised their daily vegetable and fruit intake to 12 servings. Daily intake remained high at the four-year follow-up with 65% more vegetable servings, 25% more fruit servings, 30% more fiber, and 13% less energy intake from fat compared with the control group (all P

Women with the lowest vegetable and fruit intake at baseline, 4.94 or fewer servings per day, did not have a greater benefit than other groups for breast cancer events (HR 0.97, 95% CI 0.71 to 1.34) or all-cause mortality (HR 0.75, 95% CI 0.49 to 1.14).

No consistent pattern of benefit for the high fruit and vegetable diet emerged for any other demographic, tumor characteristic, baseline diet, or cancer treatment subgroup.

Although the study could not rule out a longer-term effect of the dietary intervention, the researchers concluded that "the similarity in survival patterns between the WHEL Study groups suggests that continued follow-up would not alter the study results."

The conflict between WHEL and WINS trial results may hinge on the difference in energy balance achieved by participants, Drs. Gapstur and Khan said. In WINS, the low-fat diet group lost about 2.7 kg more than the control group by five years, whereas both groups in WHEL showed small weight gains (0.6 to 0.4 kg).

"Studies assessing whether breast cancer prognosis would be improved with interventions that focus on the complex components of energy balance (i.e., physical activity and energy intake) appear warranted," they wrote.