A Pooled Analysis of 12 Cohort Studies of Dietary Fat, Cholesterol and Egg Intake and Ovarian Cancer

Fat and cholesterol are theorized to promote ovarian carcinogenesis by increasing circulating estrogen levels. Although case–control studies have reported positive associations between total and saturated fat intake and ovarian cancer risk, two cohort studies have observed null associations. Dietary cholesterol and eggs have been positively associated with ovarian cancer risk. A pooled analysis was conducted on 12 cohort studies. Among 523,217 women, 2,132 incident epithelial ovarian cancer cases were identified. Study-specific relative risks (RR) and 95% confidence intervals (CI) were calculated by Cox proportional hazards models, and then pooled using a random effects model. Total fat intake was not associated with ovarian cancer risk (pooled multivariate RR = 1.08, 95% CI 0.86–1.34 comparing ≥45 to 30–<35% of calories). No association was observed for monounsaturated, polyunsaturated, trans-unsaturated, animal and vegetable fat, cholesterol and egg intakes with ovarian cancer risk. A weakly positive, but non-linear association, was observed for saturated fat intake (pooled multivariate RR = 1.29, 95% CI: 1.01–1.66 comparing highest versus lowest decile). Results for histologic subtypes were similar. Overall, fat, cholesterol and egg intakes were not associated with ovarian cancer risk. The positive association for saturated fat intake at very high intakes merits further investigation.     

Types of dietary fat and breast cancer: a pooled analysis of cohort studies

Recently, there has been interest in whether intakes of specific types of fat are associated with breast cancer risk independently of other types of fat, but results have been inconsistent. We identified 8 prospective studies that met predefined criteria and analyzed their primary data using a standardized approach. Holding total energy intake constant, we calculated relative risks for increments of 5% of energy for each type of fat compared with an equivalent amount of energy from carbohydrates or from other types of fat. We combined study-specific relative risks using a random effects model. In the pooled database, 7,329 incident invasive breast cancer cases occurred among 351,821 women. The pooled relative risks (95% confidence intervals [CI]) for an increment of 5% of energy were 1.09 (1.00-1.19) for saturated, 0.93 (0.84-1.03) for monounsaturated and 1.05 (0.96-1.16) for polyunsaturated fat compared with equivalent energy intake from carbohydrates. For a 5% of energy increment, the relative risks were 1.18 (95% CI 0.99-1.42) for substituting saturated for monounsaturated fat, 0.98 (95% CI 0.85-1.12) for substituting saturated for polyunsaturated fat and 0.87 (95% CI 0.73-1.02) for substituting monounsaturated for polyunsaturated fat. No associations were observed for animal or vegetable fat intakes. These associations were not modified by menopausal status. These data are suggestive of only a weak positive association with substitution of saturated fat for carbohydrate consumption; none of the other types of fat examined was significantly associated with breast cancer risk relative to an equivalent reduction in carbohydrate consumption.     

Dietary carotenoids and vitamins A, C, and E and risk of breast cancer

BACKGROUND: Data on intake of specific carotenoids and breast cancer risk are limited. Furthermore, studies of vitamins A, C, and E in relation to breast cancer risk are inconclusive. We have conducted a large, prospective study to evaluate long-term intakes of these nutrients and breast cancer risk. METHODS: We examined, by use of multivariate analysis, associations between intakes of specific carotenoids, vitamins A, C, and E , consumption of fruits and vegetables, and breast cancer risk in a cohort of 83234 women (aged 33-60 years in 1980) who were participating in the Nurses' Health Study. Through 1994, we identified 2697 incident cases of invasive breast cancer (784 premenopausal and 1913 postmenopausal). RESULTS: Intakes of beta-carotene from food and supplements, lutein/zeaxanthin, and vitamin A from foods were weakly inversely associated with breast cancer risk in premenopausal women. Strong inverse associations were found for increasing quintiles of alpha-carotene, beta-carotene, lutein/zeaxanthin, total vitamin C from foods, and total vitamin A among premenopausal women with a positive family history of breast cancer. An inverse association was also found for increasing quintiles of beta-carotene among premenopausal women who consumed 15 g or more of alcohol per day. Premenopausal women who consumed five or more servings per day of fruits and vegetables had modestly lower risk of breast cancer than those who had less than two servings per day (relative risk [RR] = 0.77; 95% confidence interval [CI] = 0.58-1.02); this association was stronger among premenopausal women who had a positive family history of breast cancer (RR = 0.29; 95% CI = 0.13-0.62) or those who consumed 15 g or more of alcohol per day (RR = 0.53; 95% CI = 0.27-1.04). CONCLUSIONS: Consumption of fruits and vegetables high in specific carotenoids and vitamins may reduce premenopausal breast cancer risk.     

Intake of specific fruits and vegetables in relation to risk of estrogen receptor-negative breast cancer among postmenopausal women

In previous studies of postmenopausal women, overall intake of fruits and vegetables groups has been inversely associated with estrogen receptor-negative (ER?) breast cancer. In this analysis, we prospectively examined the associations of specific fruits and vegetables with risk of ER? postmenopausal breast cancer among 75,929 women aged 38–63 years at baseline and followed for up to 24 years. Dietary data were collected seven times during this period. Cox proportional hazard models were used, adjusting for potential confounders, including a modified Alternate Mediterranean Diet score. We ascertained 792 incident cases of ER? postmenopausal breast cancer. The multivariate relative risk (RR) for every 2 servings/week consumption for total berries was 0.82 (95 % CI = 0.71–0.96, p = 0.01), and the RR for women who consumed at least one serving of blueberries a week was 0.69 (95 % CI = 0.50–0.95, p = 0.02) compared with non-consumers. Also, the RR for consuming at least 2 servings of peaches/nectarines per week was 0.59 (95 % CI = 0.37–0.93, p = 0.02). Risk of ER? breast cancer was not associated with intakes of other specific fruits or vegetables. In conclusion, higher intake of berries and peaches was associated with lower risk of ER? breast cancer among postmenopausal women. These results are considered exploratory and need to be confirmed in further studies.     

Fruit and vegetable intake and breast cancer risk defined by estrogen and progesterone receptor status: the Japan Public Health Center-based Prospective Study

Background

Epidemiological evidence for the impact of fruit and vegetable intake on breast cancer risk among the Japanese populations is scarce.

Objective

The purpose of this study was to evaluate the association between fruit and vegetable intake and breast cancer risk among 47,289 Japanese women.

Design

The study was conducted under a population-based prospective cohort design. Dietary assessment was performed using a validated food frequency questionnaire. A Cox proportional hazards regression model was used to calculate relative risks (RRs) and their corresponding 95 % confidence intervals (CIs).

Results

During an average of 10.2 years of follow-up, 452 cases of breast cancer were newly diagnosed. No association with breast cancer risk was seen for intake of total fruits and vegetables, cruciferous vegetables, green-leaf vegetables, yellow vegetables, or tomato products in overall or postmenopausal women. Cruciferous vegetable intake was associated with a statistically significant decrease in risk of premenopausal breast cancer [multivariable-RR_{Q4 vs. Q1} = 0.64 (95 % CI = 0.38–1.10; p _trend = .046)] and showed a marginally inverse association with ER+ PR+ tumors [RR_{per 100 g increment} = 0.64 (95 % CI = 0.41–1.00)]. In contrast, positive associations were seen between intake of total fruits and citrus fruits and breast cancer risk in overall and premenopausal women. However, these associations for fruit were all attenuated with additional adjustment for vitamin C intake.

Conclusions

Our results suggest an overall null association between total fruit and vegetable intake and breast cancer risk. Intake of cruciferous vegetable showed a statistically significant association with a decreased risk of breast cancer among premenopausal women.     

Dietary fat, fat subtypes, and breast cancer in postmenopausal women: a prospective cohort study

BACKGROUND: The intake of total dietary fat and of certain fat subtypes has been shown to be strongly associated with breast cancer in international comparisons and in animal experiments. However, observational epidemiologic studies have generally reported either weak positive or no associations. To extend the prospective epidemiologic evidence on this question, we examined the association between adult dietary intake of fat, fat subtypes, and breast cancer in a large, prospective cohort of postmenopausal women. METHODS: Participants were selected from a national breast cancer mammography screening program conducted from 1973 through 1981 at 29 centers throughout the United States. From 1987 through 1989, 40022 postmenopausal women satisfactorily completed a mailed, self-administered questionnaire that included a 60-item National Cancer Institute/Block food-frequency questionnaire. Women were then followed for an average of 5.3 years; 996 women developed breast cancer. Risk was assessed by use of Cox proportional hazard regression, with age as the underlying time metric. All statistical tests were two-sided. RESULTS: Compared with women in the lowest quintile (Q1) of percentage of energy from total fat, the adjusted risk ratio (RR) and 95% confidence interval (CI) for women in the highest quintile (Q5) was 1.07 (95% CI = 0.86-1.32). In analyses stratified by history of benign breast disease (BBD), a positive association was observed among only women with no history of BBD (RR (Q5 versus Q1) = 2.20; 95% CI = 1.41-3.42; test for trend, P =.0003). The increased risk in these women appeared to be attributable to unsaturated fat intake and oleic acid in particular. CONCLUSIONS: In this study, there was no overall association between fat intake during adulthood and breast cancer risk; however, among women with no history of BBD, there appeared to be a positive association between total and unsaturated fat intake and breast cancer risk.     

Association of diet and mammographic breast density in the Minnesota breast cancer family cohort.

Mammographic breast density is a significant risk factor for breast cancer. The present report analyzes the association of breast density and dietary factors in 1508 women in a historical cohort study of breast cancer families in Minnesota. Diet was assessed by a semiquantitative food frequency questionnaire. Percent breast density was estimated visually by a radiologist experienced in mammography. The association of percent breast density with quartiles of energy-adjusted dietary intakes was examined in analysis of covariance models adjusting for potential confounding effects of age, body mass index, and other covariates as well as correcting for familial correlation. Analyses were performed on all women combined and were also stratified by menopausal status. Among premenopausal women, percent breast density was positively associated with intakes of polyunsaturated fat, polyunsaturated:saturated fat ratio, and vitamins C and E and was inversely associated with saturated fat and total dairy intake. Among postmenopausal women, vitamin B12 was linearly associated with increased breast density. The positive associations for vitamin C and B12 were attributable to supplement intake only. There was a suggestive positive trend between breast density and daily alcohol consumption in both premenopausal and postmenopausal women. After adjustment for other sources of alcohol, only wine intake among postmenopausal women was significant such that white wine showed a positive association and red wine an inverse association with percent breast density. There was no association with other examined dietary factors. The cross-sectional differences in breast density across levels of dietary factors were small in magnitude but may have implications for breast cancer risk.     

Intake of dairy products,calcium, and vitamin d and risk of breast cancer

BACKGROUND: Laboratory data suggest that calcium and vitamin D, found at high levels in dairy products, might reduce breast carcinogenesis. However, epidemiologic studies regarding dairy products and breast cancer have yielded inconsistent results. We examined data from a large, long-term cohort study to evaluate whether high intake of dairy products, calcium, or vitamin D is associated with reduced risk of breast cancer. METHODS: We followed 88 691 women in the Nurses' Health Study cohort from the date of return of their food-frequency questionnaire in 1980 until May 31, 1996. Dietary information was collected in 1980 and updated in 1984, 1986, 1990, and 1994. We identified 3482 women (premenopausal = 827, postmenopausal = 2345, and uncertain menopausal status = 310) with incident invasive breast cancer. We used pooled logistic regression to estimate multivariable relative risks (RRs) using 2-year time increments. The RRs and 95% confidence intervals (CIs) were calculated for each category of intake compared with the lowest intake group. All statistical tests were two-sided. RESULTS: Intakes of dairy products, calcium, or vitamin D were not statistically significantly associated with breast cancer risk in postmenopausal women. In premenopausal women, however, consumption of dairy products, especially of low-fat dairy foods and skim/low-fat milk, was inversely associated with risk of breast cancer. The multivariable RRs comparing highest (>1 serving/day) and lowest (800 mg/day versus 500 IU/day versus 相似文献   

Dietary intakes of fat and fatty acids and risk of breast cancer: a prospective study in Japan

To examine the possible association of dietary fat and fatty acids with breast cancer risk in a population with a low total fat intake and a high consumption of fish, we analyzed data from the Japan Collaborative Cohort (JACC) Study. From 1988 to 1990, 26 291 women aged 40-79 years completed a questionnaire on dietary and other factors. Intakes of fat or fatty acids were estimated by using a food frequency questionnaire. Rate ratios (RR) were computed by fitting proportional hazards models. During the mean follow-up of 7.6 years, 129 breast cancer cases were documented. We found no clear association of total fat intake with breast cancer risk; the multivariate-adjusted RR across quartiles were 1.00, 1.29, 0.95, and 0.80 (95% confidence interval [CI] 0.46-1.38). A significant decrease in the risk was detected for the highest quartile of intake compared with the lowest for fish fat and long-chain n-3 fatty acids; the RR were 0.56 (95% CI 0.33-0.94) and 0.50 (0.30-0.85), respectively. A decreasing trend in risk was also suggested with an increasing intake of saturated fatty acids (trend P = 0.066). Among postmenopausal women at baseline, the highest quartile of vegetable fat intake was associated with a 2.08-fold increase in risk (95% CI 1.05-4.13). This prospective study did not support any increase in the risk of breast cancer associated with total or saturated fat intake, but it suggested the protective effects of the long-chain n-3 fatty acids that are abundant in fish.     

A prospective study of smoking and breast cancer risk among African-American women

Purpose

Active smoking and passive smoking have been associated with increased risk of breast cancer. The purpose of the present study was to prospectively assess associations of smoking with breast cancer and identify subgroups at higher risk among African-American women.

Methods

Based on 1,377 incident cases identified during 14 years of follow-up in the Black Women’s Health Study, we assessed active and passive smoking in relation to breast cancer incidence by menopausal status, estrogen receptor status, and other factors. Incidence rate ratios (IRR) and 95 % confidence intervals (CI) for categories of smoking relative to no active or passive smoking were calculated from Cox proportional hazards models, controlling for breast cancer risk factors.

Results

Active smoking was associated with increased risk of premenopausal breast cancer. The IRR was 1.21 (95 % CI 0.90–1.62) for premenopausal breast cancer overall and 1.70 (95 % CI 1.05–2.75) for premenopausal breast cancer associated with beginning smoking before age 18 together with accumulation of ≥20 pack years. The positive association with premenopausal breast cancer was most apparent for estrogen-receptor-positive cancer. Passive smoking was also associated with increased risk of premenopausal breast cancer (IRR = 1.42, 95 % CI 1.09–1.85), based on information on passive smoking at home and work. Neither active nor passive smoking was associated with increased risk of postmenopausal breast cancer.

Conclusion

These results strengthen the evidence that both active and passive smoking increase the incidence of premenopausal breast cancer.     

Reproductive factors and risk of premenopausal breast cancer by age at diagnosis: Are there differences before and after age 40?

We examined the relationship between reproductive factors and risk of premenopausal breast cancer among women less than age 40 compared with older premenopausal women. We documented 374 incident cases of breast cancer diagnosed before age 40, and 2,533 cases diagnosed at age 40 and older among premenopausal women in the Nurses’ Health Study cohorts. Biennial questionnaires were used to determine age at menarche, age at first birth, parity, breastfeeding, and other reproductive factors. Multivariate relative risks (RR) and 95 % confidence intervals (CI) were calculated using Cox proportional hazards models within age at diagnosis groups. Tumors in younger women were significantly more likely to be higher grade, larger size, and hormone receptor negative than were tumors in older premenopausal women (p < 0.0001). There was no significant heterogeneity according to age in associations between reproductive factors and risk of premenopausal breast cancer. First birth at age 30 or older increased breast cancer risk in both age groups (age <40: RR 1.10, 95 % CI 0.80–1.50; age ≥40: RR 1.16, 95 % CI 1.02–1.32; p-heterogeneity = 0.44). Risk of premenopausal breast cancer decreased with each additional year of age at menarche in both age groups (age <40: RR 0.93, 95 % CI 0.87–0.99; p trend = 0.02; age ≥40: RR 0.94, 95 % CI 0.91–0.97; p trend = <0.0001). Among premenopausal parous women, breastfeeding was protective regardless of age at diagnosis (age <40: RR 0.84, 95 % CI 0.57–1.22; age ≥40: RR 0.85, 95 % CI 0.72–0.99; p-heterogeneity = 0.79). In the largest prospective examination of reproductive risk factors and risk of breast cancer before and after age 40, we found that younger women were more likely to develop tumors with less favorable prognostic characteristics. However, associations between reproductive factors and risk of breast cancer were similar regardless of age at diagnosis of premenopausal breast cancer.     

Fat consumption and breast cancer: preliminary results from the E3N-Epic cohort]

Recent reviews have concluded that a high consumption of total, saturated or animal, fat could possibly increase the risk of breast cancer. However these results are highly dependent on the type of study; indeed, most of the prospective studies do not support this association. In this paper, we investigated the relationship between fat consumption and breast cancer risk in the E3N-Epic cohort, the French component of the European Prospective Investigation into Cancer and Nutrition. Assessment of fat consumption was based on daily intakes of food items and nutrients using a food-frequency questionnaire. Relative risk (RR) estimates were calculated using Cox's proportional hazards model. After an average of 3.4 years of follow-up, 838 cases of incident breast cancer were recorded in a study population of 65,879 women. The mean caloric intake was 2,073 kcal (SD 540), with 37% of calories coming from fat intake. Milk products and vegetable oils were the main sources of fat in the diet. We found a small positive association between fat intake and breast cancer risk. Compared with the lowest, women in the highest quartile of fat intake had a 37% higher risk of breast cancer (RR 1.37, CI95% = 0.99-1.89). There was no detectable association between fatty acids or food items contributing to fat intake and breast cancer risk. These analyses suggest there is a need for longer follow-up time to increase statistical power and confirm these tendencies.     

Fat intake and its relationship with pre- and post-menopausal breast cancer risk: a case-control study in Malaysia

Background: Fat intake has been shown to play a role in the etiology of breast cancer, but the findings have been inconsistent. Objective: To assess the association of premenopausal and postmenopausal breast cancer risk with fat and fat subtypes intake. Methodology: This is a population based case-control study conducted in Kuala Lumpur, Malaysia from January 2006 to December 2007. Food intake pattern was collected from 382 breast cancer patients and 382 control group via an interviewer-administered food frequency questionnaire. Logistic regression was used to compute odds ratios (OR) with 95% confidence intervals (CI) and a broad range of potential confounders was included in analysis. Results: This study showed that both premenopausal and postmenopausal breast cancer risk did not increase significantly with greater intake of total fat [quartile (Q) 4 versus Q1 OR=0.76, 95% CI, 0.23-2.45 and OR=1.36, 95% CI, 0.30-3.12], saturated fat (ORQ4 to Q1=1.43, 95% CI, 0.51-3.98 and ORQ4 to Q1=1.75, 95% CI, 0.62-3.40), monounsaturated fat (ORQ4 to Q1=0.96, 95% CI, 0.34-1.72 and ORQ4 to Q1=1.74, 95% CI, 0.22-2.79), polyunsaturated fat (ORQ4 to Q1=0.64, 95% CI, 0.23-1.73 and ORQ4 to Q1=0.74, 95% CI, 0.39-1.81), n-3 polyunsaturated fat (ORQ4 to Q1=1.10, 95% CI, 0.49-2.48 and ORQ4 to Q1=0.78, 95% CI, 0.28-2.18), n-6 polyunsaturated fat (ORQ4 to Q1=0.67, 95% CI, 0.24-1.84 and ORQ4 to Q1=0.71, 95% CI, 0.29-1.04) or energy intake (ORQ4 to Q1=1.52, 95% CI, 0.68-3.38 and ORQ4 to Q1=2.21, 95% CI, 0.93-3.36). Conclusion: Total fat and fat subtypes were not associated with pre- and postmenopausal breast cancer risk after controlling for age, other breast cancer risk factors and energy intake. Despite the lack of association, the effects of total fat and fat subtypes intake during premenopausal years towards postmenopausal breast cancer risk still warrant investigation.     

Body size and breast cancer risk: findings from the European Prospective Investigation into Cancer And Nutrition (EPIC)

The evidence for anthropometric factors influencing breast cancer risk is accumulating, but uncertainties remain concerning the role of fat distribution and potential effect modifiers. We used data from 73,542 premenopausal and 103,344 postmenopausal women from 9 European countries, taking part in the EPIC study. RRs from Cox regression models were calculated, using measured height, weight, BMI and waist and hip circumferences; categorized by cohort-wide quintiles; and expressed as continuous variables, adjusted for study center, age and other risk factors. During 4.7 years of follow-up, 1,879 incident invasive breast cancers were identified. In postmenopausal women, current HRT modified the body size-breast cancer association. Among nonusers, weight, BMI and hip circumference were positively associated with breast cancer risk (all ptrend < or = 0.002); obese women (BMI > 30) had a 31% excess risk compared to women with BMI < 25. Among HRT users, body measures were inversely but nonsignificantly associated with breast cancer. Excess breast cancer risk with HRT was particularly evident among lean women. Pooled RRs per height increment of 5 cm were 1.05 (95% CI 1.00-1.16) in premenopausal and 1.10 (95% CI 1.05-1.16) in postmenopausal women. Among premenopausal women, hip circumference was the only other measure significantly related to breast cancer (ptrend = 0.03), after accounting for BMI. In postmenopausal women not taking exogenous hormones, general obesity is a significant predictor of breast cancer, while abdominal fat assessed as waist-hip ratio or waist circumference was not related to excess risk when adjusted for BMI. Among premenopausal women, weight and BMI showed nonsignificant inverse associations with breast cancer.     

Dietary fat, fat subtypes, and breast cancer risk: lack of an association among postmenopausal women with no history of benign breast disease.

A recent study among 13,707 postmenopausal women without benign breast disease (BBD) from the Breast Cancer Detection Demonstration Project (BCDDP) cohort found breast cancer risk associated with greater total fat, unsaturated fat, and oleic acid intake. We assessed the associations between cumulative averaged dietary intake from 1980, 1984, 1986, and 1990 with breast cancer risk through 1994 among 44,697 postmenopausal participants without BBD in the Nurses' Health Study (NHS). Multivariate Cox proportional hazard models, with age as the time variable, provided the estimated rate ratios (RRs) with 95% confidence intervals (CIs) from the 14 years of follow-up and the 1,071 breast cancer cases. In the Nurses' Health Study, breast cancer rates over the time period from 1980 to 1994 did not increase significantly with greater total fat [quintile (Q) 5 versus Q1 RR, 0.94; 95% CI, 0.77-1.15], saturated fat (RR(Q5 to Q1), 0.88; 95% CI, 0.70-1.12), unsaturated fat (RR(Q5 to Q1), 1.16; 95% CI, 0.92-1.46), oleic acid (RR(Q5 to Q1), 1.13; 95% CI, 0.81-1.57), linoleic acid (RR(Q5 to Q1), 0.93; 95% CI, 0.74-1.16), trans fatty acid (RR(Q5 to Q1), 0.9184; 95% CI, 0.73-1.13), or energy intake (RR(Q5 to Q1), 0.81; 95% CI, 0.67-0.99). A parallel analysis restricted to the same time period as the BCDDP study did not differ substantially. We found no increase in the rate of breast cancer with greater intake of dietary fat and fat subtypes among postmenopausal women without a history of BBD.     

Long-term weight change and breast cancer risk: the European prospective investigation into cancer and nutrition (EPIC)

We examined prospectively the association between weight change during adulthood and breast cancer risk, using data on 1358 incident cases that developed during 5.8 years of follow-up among 40,429 premenopausal and 57,923 postmenopausal women from six European countries, taking part in the European prospective investigation into cancer and nutrition study. Multivariate Cox regression models were used to calculate hazard ratios according to weight change (kg), defined as the weight difference between age at enrollment and age 20 adjusted for other risk factors. Changes in weight were not associated with premenopausal breast cancer risk. In postmenopausal women, weight gain was positively associated with breast cancer risk only among noncurrent hormone replacement therapy (HRT) users (P-trend < or = 0.0002). Compared to women with a stable weight (+/-2 kg), the relative risk for women who gained 15-20 kg was 1.50 (95% confidence interval (CI) 1.06-2.13). The pooled RR per weight gain increment of 5 kg was 1.08 (95% CI 1.04-1.12). Weight gain was not associated with breast cancer risk in current HRT users, although, overall, these women experienced a much higher risk of breast cancer compared with nonusers. Our findings suggest that large adult weight gain was a significant predictor of breast cancer in postmenopausal women not taking exogenous hormones.     

A prospective study of body size and breast cancer in black women.

The relation of body mass index (BMI) and weight gain to breast cancer risk is complex, and little information is available on Black women, among whom the prevalence of obesity is high. We assessed BMI and weight gain in relation to breast cancer risk in prospective data from the Black Women's Health Study. In 1995, 59,000 African American women enrolled in the Black Women's Health Study by completing mailed questionnaires. Data on anthropometric factors were obtained at baseline and every 2 years afterwards. In 10 years of follow-up, 1,062 incident cases of breast cancer occurred. Incidence rate ratios (IRR) were computed in multivariable Cox proportional hazards regression. BMI at age 18 years of >/=25 relative to <20 was associated with a reduced risk of breast cancer among both premenopausal women (IRR, 0.68; 95% confidence interval, 0.46-0.98) and postmenopausal women (IRR, 0.53; 95% confidence interval, 0.35-0.81). There was an inverse association of current BMI with premenopausal breast cancer but no association with postmenopausal breast cancer, either overall or among never-users of hormone therapy. Weight gain was not associated with postmenopausal breast cancer risk. In analyses restricted to breast cancers that were estrogen and progesterone receptor positive, IRRs for current BMI and weight gain were elevated but not statistically significant. The findings indicate that being overweight at age 18 years is associated with a reduced risk of both premenopausal and postmenopausal breast cancer in African American women. Understanding the reasons for the association may help elucidate the pathways through which adolescent exposures influence breast cancer risk. The lack of association of obesity with receptor-negative tumors in postmenopausal African American women may partially explain why breast cancer incidence in older Black women is not high relative to other ethnic groups in spite of the high prevalence of obesity in Black women.     

The association of soy food consumption with the risk of subtype of breast cancers defined by hormone receptor and HER2 status

Soy food intake has previously been associated with reduced breast cancer risk. Epidemiological evidence for subgroups of breast cancer, particularly by menopausal and hormone receptor status, is less consistent. To evaluate the role of hormone receptor and menopausal status on the association between soy food intake and breast cancer risk, we measured usual soy food intake in adolescence and adulthood via food frequency questionnaire in 70,578 Chinese women, aged 40–70 years, recruited to the Shanghai Women's Health Study (1996–2000). After a median follow‐up of 13.2 years (range: 0.01–15.0), 1,034 incident breast cancer cases were identified. Using Cox models, we found that adult soy intake was inversely associated with breast cancer risk [hazard ratio (HR) for fifth versus first quintile soy protein intake = 0.78; 95% confidence interval (CI):0.63–0.97]. The association was predominantly seen in premenopausal women (HR = 0.46; 95% CI:0.29‐0.74). Analyses further stratified by hormone receptor status showed that adult soy intake was associated with significantly decreased risk of estrogen receptor (ER)+/progesterone receptor (PR)+ breast cancer in postmenopausal women (HR = 0.72; 95% CI:0.53–0.96) and decreased risk of ER?/PR? breast cancer in premenopausal women (HR = 0.46; 95% CI:0.22–0.97). The soy association did not vary by human epidermal growth factor‐2 (HER2) status. Furthermore, we found that high soy intake during adulthood and adolescence was associated with reduced premenopausal breast cancer risk (HR = 0.53; 95% CI: 0.32–0.88; comparing third vs. first tertile) while high adulthood soy intake was associated with postmenopausal breast cancer only when adolescent intake was low (HR = 0.63; 95% CI: 0.43–0.91). Our study suggests that hormonal status, menopausal status and time window of exposure are important factors influencing the soy‐breast cancer association.     

Dietary glycaemic index, glycaemic load and breast cancer risk: a systematic review and meta-analysis

This systematic review aimed to examine if an association exists between dietary glycaemic index (GI) and glycaemic load (GL) intake and breast cancer risk. A systematic search was conducted in Medline and Embase and identified 14 relevant studies up to May 2008. Adjusted relative risk estimates comparing breast cancer risk for the highest versus the lowest category of GI/GL intake were extracted from relevant studies and combined in meta-analyses using a random-effects model. Combined estimates from six cohort studies show non-significant increased breast cancer risks for premenopausal women (relative risk (RR) 1.14, 95% CI 0.95-1.38) and postmenopausal women (RR 1.11, 95% CI 0.99-1.25) consuming the highest versus the lowest category of GI intake. Evidence of heterogeneity hindered analyses of GL and premenopausal risk, although most studies did not observe any significant association. Pooled cohort study results indicated no association between postmenopausal risk and GL intake (RR 1.03, 95% CI 0.94-1.12). Our findings do not provide strong support of an association between dietary GI and GL and breast cancer risk.     

Circulating levels of insulin-like growth factors, their binding proteins, and breast cancer risk.

BACKGROUND: Earlier data support the hypothesis that the relation between circulating insulin-like growth factor-I (IGF-I) levels and breast cancer risk differs by menopausal status. The strong association of IGF-I with height in childhood and weak or no association between adult levels and adult height also suggest that IGF levels in young women may better reflect an exposure time period of importance to breast cancer. Few studies have assessed IGF binding protein-1 (IGFBP-1) or free IGF and breast cancer risk. MATERIALS AND METHODS: We conducted a large case-control study nested within the prospective Nurses' Health Study. Plasma concentrations of IGF-I, free IGF, IGFBP-3, and IGFBP-1 were measured in blood samples collected in 1989 to 1990. Eight hundred women were identified who had a diagnosis of invasive or in situ breast cancer after blood collection, up to 1998, 27% of whom were premenopausal at blood collection. To those 800 women, one to two controls were age-matched for a total of 1,129 controls. We used logistic regression models to estimate the relative risk (RR) of breast cancer associated with IGF levels.Findings: Among postmenopausal women, neither IGF-I, IGFBP-3, IGFBP-1, nor free IGF was associated with breast cancer risk [RRs, top versus bottom quintile: IGF-I, 1.0; 95% confidence interval (95% CI), 0.7-1.4; IGFBP-3, 0.8; 95% CI, 0.6-1.1; IGFBP-1, 0.9; 95% CI, 0.6-1.5; and free IGF, 1.0; 95% CI, 0.6-1.4]. Among premenopausal women, IGFBP-3, IGFBP-1, and free IGF similarly were not associated with breast cancer risk (RRs, top versus bottom quintile: IGFBP-3, 1.2; 95% CI, 0.8-2.3; IGFBP-1, 1.5; 95% CI, 0.8-3.0; and free IGF, 1.1; 95% CI, 0.7-2.1). Higher IGF-I plasma levels, however, were associated with a modestly elevated breast cancer risk (RR, 1.6; 95% CI, 1.0-2.6) among the premenopausal women, with a stronger association among premenopausal women ages < or =50 (RR, 2.5; 95% CI, 1.4-4.3); further adjustment for IGFBP-3 did not greatly change these estimates. INTERPRETATION: Circulating IGF-I levels seem to be modestly associated with breast cancer risk among premenopausal women, but not among postmenopausal women. IGFBP-3, IGFBP-1, and free IGF are not associated with breast cancer risk in either premenopausal or postmenopausal women in this cohort.