Baseline characteristics of the study participants according to total fruit intake and total vegetable intake are presented in . Women who consumed more fruits or vegetables were more likely to be older, to live in the northeastern and western regions of the United States, to be physically active and nonsmokers, and to take multivitamins. Educational level was positively associated with vegetable consumption.
Baseline Characteristics According to Intake of Fruits and Vegetables in the Black Women's Health Study, 1995
During 554,528 person-years of follow-up, we identified 1,268 cases of breast cancer; 562 cases (44%) were premenopausal, 570 (45%) were postmenopausal, and 136 (11%) had uncertain menopausal status. Among 745 cases with known hormone receptor status, 366 (49%) were ER+/PR+, 103 (14%) were ER+/PR−, 12 (2%) were ER−/PR+, and 264 (35%) were ER−/PR−. Among 310 premenopausal cases with known receptor status, 47% were ER+/PR+, 12% were ER+/PR−, 2% were ER−/PR+, and 39% were ER−/PR−; among 341 postmenopausal cases with known receptor status, the corresponding percentages were 50%, 16%, 2%, and 32%. Cases with known and unknown hormone receptor status were similar with respect to fruit and vegetable intake, age, education, and other lifestyle and reproductive factors.
Median intakes of total fruit and total vegetables were 0.7 servings/day and 1.0 servings/day, respectively. Total fruit, total vegetable, and total fruit and vegetable intakes were not significantly associated with breast cancer risk overall (). The multivariable incidence rate ratios were 0.87 (95% confidence interval (CI): 0.71, 1.07) for ≥4 servings/day of fruits and vegetables relative to <1/day, 0.87 (95% CI: 0.73, 1.05) for ≥2 servings/day of vegetables compared with <4/week, and 0.91 (95% CI: 0.74, 1.11) for ≥2 servings/day of fruits relative to <2/week. However, there was an inverse association with cruciferous vegetable intake; the incidence rate ratios for 1–2, 3–5, and ≥6 servings/week compared with <1/week were 0.94 (95% CI: 0.80, 1.11), 1.01 (95% CI: 0.84, 1.21), and 0.80 (95% CI: 0.65, 0.99), respectively (Ptrend = 0.06). The association was stronger among premenopausal women (incidence rate ratio (IRR) = 0.59, 95% CI: 0.42, 0.83, for ≥6 servings/week relative to <1/week), whereas there was no evidence of an association among postmenopausal women (Pinteraction = 0.007). However, when we excluded women who had ever used menopausal hormones, there was a nonsignificant inverse association between cruciferous vegetable intake and risk of postmenopausal breast cancer (IRR = 0.74, 95% CI: 0.43, 1.26, for ≥6 servings/week relative to <1/week). There was also some evidence of an inverse association between yellow-orange vegetable intake and breast cancer risk overall; the incidence rate ratio was 0.87 (95% CI: 0.72, 1.05) for ≥6 servings/week compared with <1/week (Ptrend = 0.13). Results for yellow-orange vegetable intake did not differ significantly by menopausal status (Pinteraction = 0.88).
Intake of Fruits and Vegetables in Relation to Risk of Breast Cancer in the Black Women's Health Study, 1995–2007
Because of the previous finding of an inverse association between a prudent dietary pattern and breast cancer risk among subgroups of women in the Black Women's Health Study (22
), in a subanalysis of fruit and vegetable intake in relation to breast cancer risk, we controlled for the other major components of a prudent dietary pattern, that is, whole grains and fish. The results were unchanged (data not shown).
There was no evidence of effect modification of fruit and vegetable intake in relation to breast cancer risk according to age, body mass index, smoking status, or multivitamin use (data not shown).
presents results for individual vegetables and fruit in relation to breast cancer risk overall and according to menopausal status. The incidence rate ratios for the highest categories of consumption of each cruciferous vegetable (broccoli, collard greens, and cabbage), though not significant, were each compatible with a decreased risk of breast cancer overall. Carrot intake was inversely associated with overall breast cancer risk; the incidence rate ratio was 0.83 (95% CI: 0.67, 1.04) for ≥3 servings/week relative to <1/month (Ptrend = 0.02).
Intake of Individual Fruits and Vegetables in Relation to Risk of Breast Cancer in the Black Women's Health Study, 1995–2007
Total vegetable intake was associated with a significant reduction in risk of ER−/PR− breast cancer (); the incidence rate ratios were 0.71 (95% CI: 0.50, 1.01), 0.79 (95% CI: 0.57, 1.10), and 0.57 (95% CI: 0.38, 0.85) for 4–6 servings/week, 1/day, and ≥2/day, respectively, compared with <4/week (Ptrend = 0.02). Conversely, for ER+/PR+ breast cancer, the incidence rate ratios for total vegetable intake were above 1; the corresponding incidence rate ratios were 1.40 (95% CI: 0.99, 1.99), 1.54 (95% CI: 1.11, 2.14), and 1.41 (95% CI: 0.97, 2.04). For ER−/PR− breast cancer, there was a reduced risk for higher levels of intake for each vegetable subclass, but the confidence intervals were compatible with 1. For ER+/PR+ and ER+/PR− breast cancer, there was no consistent pattern by type of vegetable. Neither citrus fruit nor other fruit was materially associated with risk of breast cancer subtypes. Results are not presented for ER−/PR+ breast cancer because the number of cases was too small for meaningful interpretations. Results for ER− breast cancer were similar to those for ER−/PR− breast cancer, and results for ER+ breast cancer were similar to those for ER+/PR+ breast cancer (data not shown). We had limited power to evaluate associations jointly by ER/PR status and menopausal status, but results for breast cancer hormone receptor subtypes appeared to be similar across menopausal status (data not shown).
Intake of Fruits and Vegetables in Relation to Risk of Breast Cancer by ER/PR Status in the Black Women's Health Study, 1995–2007
When individual vegetables and fruit were considered in relation to breast cancer risk according to ER/PR status (data not shown), the incidence rate ratios were less than 1 for the association of ER−/PR− breast cancer with the highest intake categories of broccoli, collard greens, cabbage, spinach, green salad, and yams, but only the incidence rate ratio for intake of yams ≥1/week relative to <1/month was statistically significant (IRR = 0.59, 95% CI: 0.35, 0.98). There were no consistent trends for ER+/PR+ or ER+/PR− breast cancer.