Plant foods and oestrogen receptor alpha- and beta-defined breast cancer: observations from the Malmo Diet and Cancer cohort

Nut consumption in association with overall mortality and recurrence/disease-specific mortality among long-term breast cancer survivors

High nut consumption is associated with reduced total and certain cause-specific mortality in general populations. However, its association with cancer outcomes among long-term breast cancer survivors remains unknown. We examined the associations of nut consumption (including peanuts and tree nuts), assessed at 5-year postdiagnosis, with overall survival (OS) and disease-free survival (DFS) among 3449 long-term breast cancer survivors from the Shanghai Breast Cancer Survival Study, applying Cox regression analysis. During a median follow-up of 8.27 years post dietary assessment, there were 374 deaths, including 252 breast cancer deaths. Among 3274 survivors without previous recurrence at the dietary assessment, 209 developed breast cancer-specific events, that is, recurrence, metastasis or breast cancer mortality. At 5-year post dietary assessment (ie, 10-year postdiagnosis), regular nut consumers had higher OS (93.7% vs 89.0%) and DFS (94.1% vs 86.2%) rates. After multivariable adjustment, nut consumption was positively associated with OS (P_trend  = .022) and DFS (P_trend  = .003) following a dose-response pattern, with hazard ratios (95% confidence interval) of 0.72 (0.52-1.05) for OS and 0.48 (0.31-0.73) for DFS, for participants with greater than median nut intake compared with nonconsumers. The associations did not vary by nut type. Stratified analyses showed that the associations were more evident among participants with a higher total energy intake for OS (P_interaction  = .02) and among participants with early stage (I-II) breast cancers for DFS (P_interaction  = .04). The nut-DFS associations were not modified by estrogen receptor/progesterone receptor status or other known prognostic factors. In conclusion, nut consumption was associated with better survival, particularly DFS, among long-term breast cancer survivors.

Association of nut consumption with risk of total cancer and 5 specific cancers: evidence from 3 large prospective cohort studies

BACKGROUND

The associations between nut consumption and cancer risk have not been extensively investigated.

OBJECTIVES

We aimed to examine the associations between nut consumption, especially specific types of nuts (peanut, tree nut, walnut, and tree nut other than walnut), and cancer risk.

METHODS

Nut consumption was assessed by FFQ at baseline and updated every 2-4 y in the Nurses' Health Study (1980-2014), the Nurses' Health Study II (1991-2015), and the Health Professionals Follow-up Study (1986-2018). We examined the associations between the intake of total and specific types of nuts and risk of total cancer and common cancers, including lung, colorectal, breast, bladder, and aggressive prostate cancer. Cox proportional-hazards models were used to obtain the HRs and 95% CIs in each cohort as well as pooled.

RESULTS

During 5,873,671 person-years of follow-up in 180,832 women and 45,560 men, we documented 44,561 incident cancer cases. As compared with nonconsumers, the pooled multivariable HRs of total nut consumption for ≥5 times/wk were 0.99 (95% CI: 0.94, 1.04; P-trend = 0.54) for total cancer, 0.88 (95% CI: 0.74, 1.04; P-trend = 0.18) for lung cancer, 1.07 (95% CI: 0.92, 1.26; P-trend = 0.89) for colorectal cancer, 0.90 (95% CI: 0.71, 1.14; P-trend = 0.65) for bladder cancer, 0.96 (95% CI: 0.85, 1.08; P-trend = 0.36) for breast cancer, and 1.18 (95% CI: 0.92, 1.51; P-trend = 0.52) for aggressive prostate cancer.

CONCLUSIONS

In 3 large prospective cohorts, frequent nut consumption was not associated with risk of total cancer and common individual cancers.

Food Quality Score and Risk of Breast Cancer among Iranian Women: Findings from a Case Control Study

The quality of foods we consume may be an important risk factor for breast cancer (BrCa); however, relations between quality of food metrics and BrCa risk have not been systematically investigated. The purpose of this study was to examine the association between food quality score (FQS) by assessing the intake of healthy and unhealthy food and the odds of (BrCa) among Iranian women. This hospital-based case-control study was carried out on 150 women with pathologically confirmed breast cancer within the past three months and 150 healthy controls that were age-match from the Cancer Research Center, Imam Khomeini hospital, Iran. Participants were interviewed to obtain data relating to diet (using a 147-item validated FFQ) and BrCa risk factors. We found a significant association between adherence to the FQS and odds of breast cancer in the fully adjusted model (OR: 0.58; P = 0.04) and in premenopausal women in the fully adjusted model (OR: 0.45; P = 0.02); however, we did not observe any association between postmenopausal women in the adjusted model (OR: 0.76; P = 0.5). We also failed to observe any association between healthy (p = 0.3) and unhealthy subgroups (p = 0.3) of FQS. Our findings suggest that adherence to FQS may be associated with an increased risk of breast cancer in crude and adjusted models in overall and premenopausal women. However, we did not see any association between FQS and BrCa risk in postmenopausal women. Prospective cohort studies are needed to confirm these findings.Supplemental data for this article is available online at https://doi.org/10.1080/01635581.2021.1957136 .

Fruit and vegetable consumption and incident breast cancer: a systematic review and meta-analysis of prospective studies

BACKGROUND

We conducted a systematic review and meta-analysis of prospective studies to clarify the relation of fruit and vegetable consumption with incident breast cancer.

METHODS

We searched systematically PubMed and EMBASE databases up to November 2020 to include prospective studies that reported the association of fruit and vegetable consumption with incident breast cancer. The pooled relative risks (RRs) and 95% confidence intervals (CIs) were calculated for the highest versus the lowest category of total fruit and vegetable, total fruit and total vegetable consumption, as well as fruit juice and subgroups of vegetables in relation to breast cancer incidence, using a random-effect model.

RESULTS

Total fruit and vegetable consumption was associated with lower overall (RR = 0.91, 95% CI = 0.87-0.95) and postmenopausal breast cancer risk (RR = 0.88, 95% CI = 0.79-0.99). Total fruit consumption was associated with lower overall (RR = 0.93, 95% CI = 0.88-0.99) and postmenopausal breast cancer risk (RR = 0.93, 95% CI = 0.87-0.99). Total fruit and vegetable intake were associated with 11% and 26% lower risk of oestrogen- and progesterone-receptor-positive (ER+/PR+) and -negative (ER-/PR-) breast cancer, respectively. Total vegetable consumption was associated with 27% lower risk of ER-/PR- breast cancer. Fruit juice consumption was associated with increased overall breast cancer risk (RR = 1.04, 95% CI = 1.01-1.07). We did not find significant associations for subgroups of vegetable intake and breast cancer risk.

CONCLUSIONS

These findings suggest that high total fruit and vegetable consumption are associated with reduced risk of overall, postmenopausal, ER+/PR+ and ER-/PR- breast cancer.

Potato Consumption and Risk of Site-Specific Cancers in Adults: A Systematic Review and Dose-Response Meta-Analysis of Observational Studies

The etiology of cancer type may vary significantly due to anatomy, embryology, and physiology of the cancer site. Although the association between potato consumption and colorectal cancer (CRC) was summarized in a 2018 meta-analysis of 5 cohort studies, to the best of our knowledge, no meta-analysis has evaluated potato consumption in relation to multiple cancer sites in adults. Medline/PubMed, ISI Web of Knowledge, Scopus, and the Cochrane Database of Systematic Reviews were searched for relevant publications through August 2020. We selected cohort or case-control studies conducted in adults that reported risk estimates (relative risk [RRs], HRs, and ORs) of potato intake for any cancer type. Random effects meta-analyses compared high and low intake categories. Twenty prospective cohort studies (total n = 785,348) including 19,882 incident cases, and 36 case-control studies (21,822 cases; 66,502 controls) were included. Among cohort studies, we did not find an association between high versus low intake of total potato (white and yellow) consumption and overall cancers: 1.04 (95% CI: 0.96, 1.11; tau2 = 0.005, n = 18). We found no relation between total potato consumption (high compared with low intake) and risk of CRC, pancreatic cancer, colon, gastric, breast, prostate, kidney, lung, or bladder cancer in cohort or case-control studies. We did not find an association between high versus low consumption of potato preparations (boiled/fried/mashed/roasted/baked) and risk of gastrointestinal-, sex-hormone-, or urinary-related cancers in cohort or case-control studies. Certainty of the evidence was low for total cancer, CRC, colon, rectal, renal, pancreatic, breast, prostate, and lung cancer and very low for gastric and bladder cancer. In conclusion, potato intake or potato preparations were not associated with multiple cancer sites when comparing high and low intake categories. This finding was consistent with the findings from the 2018 meta-analysis regarding potato intake and risk of CRC.

Association of Total Nut, Tree Nut, Peanut, and Peanut Butter Consumption with Cancer Incidence and Mortality: A Comprehensive Systematic Review and Dose-Response Meta-Analysis of Observational Studies

Data on the association of nut intake with risk of cancer and its mortality are conflicting. Although previous meta-analyses summarized available findings in this regard, some limitations may distort their findings. Moreover, none of these meta-analyses examined the dose-response associations of total nut intake with the risk of specific cancers as well as associations between specific types of nuts and cancer mortality. Therefore, this study aimed to summarize available findings on the associations of total nut (tree nuts and peanuts), tree nut (walnuts, pistachios, macadamia nuts, pecans, cashews, almonds, hazelnuts, and Brazil nuts), peanut (whole peanuts without considering peanut butter), and peanut butter consumption with risk of cancer and its mortality by considering the above-mentioned points. We searched the online databases until March 2020 to identify eligible articles. In total, 43 articles on cancer risk and 9 articles on cancer mortality were included in the current systematic review and meta-analysis. The summary effect size (ES) for risk of cancer, comparing the highest with lowest intakes of total nuts, was 0.86 (95% CI: 0.81, 0.92, P < 0.001, I2 = 58.1%; P < 0.01), indicating a significant inverse association. Such a significant inverse association was also seen for tree nut intake (pooled ES: 0.87, 95% CI: 0.78-0.96, P < 0.01, I2 = 15.8%; P = 0.28). Based on the dose-response analysis, a 5-g/d increase in total nut intake was associated with 3%, 6%, and 25% lower risks of overall, pancreatic, and colon cancers, respectively. In terms of cancer mortality, we found 13%, 18%, and 8% risk reductions with higher intakes of total nuts, tree nuts, and peanuts, respectively. In addition, a 5-g/d increase in total nut intake was associated with a 4% lower risk of cancer mortality. In conclusion, our findings support the protective association between total nut and tree nut intake and the risk of cancer and its mortality.

Whole Grains, Refined Grains, and Cancer Risk: A Systematic Review of Meta-Analyses of Observational Studies

PubMed, Web of Science, and the Cochrane Database of Systematic Reviews were searched for meta-analyses that provided risk estimates (±95% confidence intervals) for associations between intakes of whole and refined grains and risk of total and site-specific cancer. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were followed. Only meta-analyses that included whole grains and refined grains as separate food groups, and not as part of dietary patterns, were included. A total of 17 publications were identified that met inclusion criteria. Within these, results from a total of 54 distinct meta-analyses were reported for whole grains and 5 meta-analyses for refined grains. For total cancer mortality, 7 meta-analyses of cohort studies indicated that whole grain intake was associated with 6% to 12% lower risk in comparison of highest vs. lowest intake groups, and 3% to 20% lower risk for doses ranging from 15 to 90 g/day. For site-specific cancers, meta-analyses indicated that whole grain intake was consistently associated with lower risks of colorectal, colon, gastric, pancreatic, and esophageal cancers. Limited data were available for refined grains, with only 4 publications providing risk estimates, and only 1 of the meta-analyses included more than 3 studies. High intake of refined grains was associated with increased risk of colon and gastric cancer. By contrast, in the only dose-response meta-analysis, each 90 g/day consumption of refined grains was associated with a 6% lower risk of total cancer. In addition to the limited number of published meta-analyses on refined grains, results were also weakened due to the fact that refined grains were frequently defined to include both staple grain foods and indulgent grain foods, and the majority of studies included in the meta-analyses provided no specific definition of refined grains. Overall, meta-analyses of cohort and case-control studies consistently demonstrate that whole grain intake is associated with lower risk of total and site-specific cancer, and support current dietary recommendations to increase whole grain consumption. By contrast, the relationship between refined grain intake and cancer risk is inconclusive.

Intake of Various Food Groups and Risk of Breast Cancer: A Systematic Review and Dose-Response Meta-Analysis of Prospective Studies

Despite increasing evidence for the association of food-based dietary patterns with breast cancer risk, knowledge about the shape of the relationship and the quality of meta-evidence are insufficient. We aimed to summarize the associations between food groups and risks of breast cancer. We performed a systematic literature search of the PubMed and Embase databases up to March 2020. We included cohort, case-cohort, nested case-control studies, and follow-up studies of randomized controlled trials that investigated the relationship between breast cancer risk and at least 1 of the following food groups: red meat, processed meat, fish, poultry, egg, vegetables, fruit, dairy product (overall, milk, yogurt, and cheese), grains/cereals, nuts, legumes, soy, and sugar-sweetened beverages. Summary risk ratios (RRs) and 95% CIs were estimated using a random-effects model for linear and nonlinear relationships. Inverse linear associations were observed for vegetables (RR per 100 g/d, 0.97; 95% CI, 0.95-0.99), fruit (RR per 100 g/d, 0.97; 95% CI, 0.95-0.99), cheese (RR per 30 g/d, 0.95; 95% CI, 0.91-1.00), and soy (RR per 30 g/d, 0.96; 95% CI, 0.94-0.99), while positive associations were observed for red (RR per 100 g/d, 1.10; 95% CI, 1.03-1.18) and processed meat (RR per 50 g/d, 1.18; 95% CI, 1.04-1.33). None of the other food groups were significantly associated with breast cancer risk. A nonlinear association was observed only for milk, such that the intake of >450 g/d increased the risk, while no association was observed for lower intake amounts. High intakes of vegetables, fruit, cheese, and soy products and low intakes of red and processed meat were associated with lower risks of breast cancer. However, causality cannot be inferred from these statistical correlations.

Multi-Grain Rice Diet Decreases Risk of Breast Cancer in Korean Women: Results from the Health Examinees Study

Although a number of studies explain the association between dietary patterns, which take into account that foods are eaten in combination, and breast cancer risk, the findings are inconsistent. We examined the association between dietary patterns and multi-grain rice intake, and the risk of breast cancer in a large-scale prospective cohort study in Korean women. A total of 93,306 women aged 40–69 years from the Health Examinees-Gem (HEXA-G) study (2004 and 2013) were included. We obtained Information on cancer diagnosis via linkage to the Korea Central Cancer Registry. Factor analysis was conducted to obtain dietary patterns, and Cox proportional models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (95% CI) for breast cancer risk. For 494,490 person-years, 359 new cases of breast cancer occurred. We identified three major dietary patterns, that explained 23.9% of the total variance based on daily total food intake (g/day) from 37 food groups: the meat dietary pattern (higher intake of bread and red meat), the white rice dietary pattern (higher intake of white rice and lower intake of multi-grain rice), and the other pattern. Women who had higher white rice dietary pattern scores had a 35% higher risk of breast cancer, than did women with lower white rice dietary pattern scores (multivariable HR 1.35; 95% CI 1.00–1.84 for the highest vs. lowest quartile of the white rice dietary pattern scores, p for trend = 0.0384). We found that women who consumed three or more servings of multi-grain rice per day had 33% lower risk of breast cancer than did those who consumed one or less multi-grain rice serving per day among women under 50 years of age (multivariable HR 0.67; 95% CI 0.45–0.99, p for trend = 0.0204). Our study suggests that a multi-grain rice diet may be associated with lower risk of breast cancer in Korean women.

Legume and Nuts Consumption in Relation to Odds of Breast Cancer: A Case-Control Study

Previous studies on the association between legume and nuts intake and risk of breast cancer have mainly been focused on individual components of legume or nuts, rather than consumption of the whole food group. This study aimed to investigate the relation between legume and nuts intake in relation to breast cancer in Iranian women. In this population-based case-control study, we enrolled 350 pathologically confirmed new cases of breast cancer and 700 controls which were matched with cases in terms of age and socioeconomic status. Dietary intakes were assessed using a validated block-format 168-item semi-quantitative food frequency questionnaire. Legume intake was computed by summing up the consumption of lentils, peas, chickpeas, and different kinds of beans, including red beans and pinto beans. To calculate nuts consumption, we summed up intake of mixed nuts, almond, peanut, walnut and hazelnut. Data on potential confounding variables were also collected using pre-tested questionnaires. Mean consumption of legume and nuts among cases and controls were 14.7 ± 15.0 and 2.3 ± 5.6, respectively. A significant inverse association was found between legume intake and breast cancer (OR: 0.41, 95% CI: 0.30-0.57); such that after adjusting for confounders, participants in the top tertile of legume intake had 46% lower odds of breast cancer compared with those in the bottom tertile (OR: 0.54, 95% CI: 0.36-0.88). Such inverse association was seen among postmenopausal women (OR: 0.51, 95% CI: 0.31-0.85) and also among normal-weight participants (OR: 0.49, 95% CI: 0.29-0.82). In terms of nuts intake, it was inversely associated with odds of breast cancer (OR: 0.16, 95% CI: 0.11-0.23). This association remained significant even after taking potential confounders into account (OR: 0.15, 95% CI: 0.09-0.26). The same association was also seen in premenopausal women (OR: 0.21, 95% CI: 0.14-0.31), postmenopausal women (OR: 0.23, 95% CI: 0.13-0.42), normal-weight (OR: 0.15, 95% CI: 0.08-0.28), and overweight or obese people (OR: 0.27, 95% CI: 0.10-0.71). Our findings on the inverse association of legume and nuts intake with odds of breast cancer support the current recommendations on these foods. Prospective studies are needed to further examine this link.

Fiber consumption and breast cancer incidence: A systematic review and meta-analysis of prospective studies

BACKGROUND

Associations between fiber intake and breast cancer risk have been evaluated in prospective studies, but overall, the evidence is inconsistent. The authors performed a systematic review and meta-analysis of prospective studies to investigate the relation between intake of total and types of fiber with breast cancer incidence.

METHODS

The MEDLINE and Excerpta Medica dataBASE (EMBASE) databases were searched through July 2019 for prospective studies that reported on the association between fiber consumption and incident breast cancer. The pooled relative risk (RR) and 95% confidence intervals (95% CI) were estimated comparing the highest versus the lowest category of total and types of fiber consumption, using a random-effects meta-analysis.

RESULTS

The authors identified 17 cohort studies, 2 nested case-control studies, and 1 clinical trial study. Total fiber consumption was associated with an 8% lower risk of breast cancer (comparing the highest versus the lowest category, pooled RR, 0.92; 95% CI, 0.88-0.95 [I²  = 12.6%]). Soluble fiber was found to be significantly inversely associated with risk of breast cancer (pooled RR, 0.90 [95% CI, 0.84-0.96; I² = 12.6%]) and insoluble fiber was found to be suggestively inversely associated with risk of breast cancer (pooled RR, 0.93 [95% CI, 0.86-1.00; I² = 33.4%]). Higher total fiber intake was associated with a lower risk of both premenopausal and postmenopausal breast cancers (pooled RR, 0.82 [95% CI, 0.67-0.99; I²  = 35.2%] and pooled RR, 0.91 [95% CI, 0.88-0.95; I²  = 0.0%], respectively). Furthermore, the authors observed a nonsignificant inverse association between intake of total fiber and risk of both estrogen and progesterone receptor-positive and estrogen and progesterone receptor-negative breast cancers.

CONCLUSIONS

A random-effects meta-analysis of prospective observational studies demonstrated that high total fiber consumption was associated with a reduced risk of breast cancer. This finding was consistent for soluble fiber as well as for women with premenopausal and postmenopausal breast cancer.

Nut Consumption and Risk of Cancer: A Meta-analysis of Prospective Studies

BACKGROUND

Epidemiologic studies have investigated the association between nut intake and risk for multiple cancers. However, current findings are inconsistent and no definite conclusion has been drawn from prospective studies. We therefore conducted this meta-analysis to evaluate the relationship between nut consumption and risk of cancer.

METHODS

Prospective studies reporting associations between nut intake and risk for all types of cancer were identified by searching Web of Science and PubMed databases up to June 2019. Risk ratios (RR) and 95% confidence intervals (CI) were extracted and then pooled across the studies using a random-effect model. A dose-response analysis was modeled by performing restricted cubic splines when data were available.

RESULTS

Thirty-three studies that included more than 50,000 cancer cases were eligible for the analysis. When comparing the highest with the lowest category of nut intake, high consumption of nuts was significantly associated with decreased risk of overall cancer (RR = 0.90; 95% CI, 0.85-0.95). The protective effect of nut consumption was especially apparent against cancers from the digestive system (RR = 0.83; 95% CI, 0.77-0.89). Among different nut classes, significant association was only obtained for intake of tree nuts. We also observed a linear dose-response relationship between nut consumption and cancer: Per 20 g/day increase in nut consumption was related to a 10% (RR = 0.90; 95% CI, 0.82-0.99) decrease in cancer risk.

CONCLUSIONS

Our analysis demonstrated an inverse association of dietary nut consumption with cancer risk, especially for cancers from the digestive system.

IMPACT

This study highlights the protective effect of nuts against cancer.

Plant Foods, Antioxidant Biomarkers, and the Risk of Cardiovascular Disease, Cancer, and Mortality: A Review of the Evidence

Although a high intake of plant foods such as fruits, vegetables, whole grains, nuts, and legumes has been recommended for chronic disease prevention, it has been unclear what is the optimal amount of intake of these foods and whether specific subtypes are particularly beneficial. The evidence from several recently published meta-analyses on plant foods and antioxidants and various health outcomes is reviewed as well as more recently published studies. In meta-analyses of prospective studies, inverse associations were observed between intake of fruits, vegetables, whole grains, and nuts and the risk of coronary artery disease, stroke, cardiovascular disease overall, total cancer, and all-cause mortality. The strongest reductions in risk were observed at an intake of 800 g/d for fruits and vegetables, 225 g/d for whole grains, and 15-20 g/d for nuts, respectively. Whole-grain and nut consumption was also inversely associated with mortality from respiratory disease, infections, and diabetes. Stronger and more linear inverse associations were observed between blood concentrations of antioxidants (vitamin C, carotenoids, vitamin E) and cardiovascular disease, cancer, and all-cause mortality than for dietary intake. Most studies that have since been published have been consistent with these results; however, further studies are needed on subtypes of plant foods and less common causes of death. These results strongly support dietary recommendations to increase intake of plant foods, and suggest optimal intakes for chronic disease prevention may be ∼800 g/d for intakes of fruits and vegetables, 225 g/d for whole grains, and 15-20 g/d for nuts. Diets high in plant foods could potentially prevent several million premature deaths each year if adopted globally.

Fruit and vegetable consumption and breast cancer incidence: Repeated measures over 30 years of follow-up

We evaluated the relation of fruit and vegetable consumption, including specific fruits and vegetables, with incident breast cancer characterized by menopausal status, hormone receptor status and molecular subtypes. Fruit and vegetable consumption, cumulatively averaged across repeated, validated questionnaires, was examined in relation to risk of invasive breast cancer among 182,145 women initially aged 27-59 years in the Nurses' Health Study (NHS, 1980-2012) and NHSII (1991-2013). Cox proportional hazards regression, adjusted for known risk factors, was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) and assessed tumors by hormone receptor status and molecular subtypes. We prospectively documented 10,911 invasive breast cancer cases. Greater intake of total fruits and vegetables, especially cruciferous and yellow/orange vegetables, was associated with significantly lower breast cancer risk (>5.5 vs. ≤2.5 servings/day HR = 0.89, 95% CI = 0.83-0.96; ptrend = 0.006). Intake of total vegetables was especially associated with lower risk of estrogen receptor negative tumors (HR per 2 additional servings/day as a continuous variable = 0.84, 95%CI = 0.77-0.93; pheterogeneity = 0.02). Among molecular subtypes, higher intake of total fruits and vegetables (HR per 2 additional servings/day as a continuous variable) was most strongly associated with lower risk of human epidermal growth factor receptor 2 (HER2)-enriched (HR = 0.79, 95%CI = 0.67-0.93), basal-like (HR = 0.84, 95%CI = 0.72-0.97) and luminal A (HR = 0.94, 95%CI = 0.89-0.99), but not with luminal B tumors (pheterogeneity = 0.03). In conclusion, our findings support that higher intake of fruits and vegetables, and specifically cruciferous and yellow/orange vegetables, may reduce the risk of breast cancer, especially those that are more likely to be aggressive tumors.

Association between whole grain intake and breast cancer risk: a systematic review and meta-analysis of observational studies

Background

Epidemiological studies have found that high whole grain intake may be associated with a reduced risk of breast cancer. However, the evidence has not been consistent. We conducted a meta-analysis to quantitatively assess the association between whole grain intake and breast cancer risk.

Methods

Relevant observational studies were identified by searching PubMed, Embase, Cochrane library databases, and Google Scholar through April 2017. Summary relative risk (RR) estimates were calculated using random-effects meta-analysis.

Results

A total of 11 studies, including 4 cohort and 7 case-control studies and involving 131,151 participants and 11,589 breast cancer cases, were included in the current meta-analysis. The pooled RR of breast cancer for those with high versus low whole grain intake was 0.84 (95% confidence interval [CI]: 0.74 to 0.96, p = 0.009; I² = 63.8%, p_{for heterogeneity} = 0.002). Subgroup analysis by study design found a significant inverse association in the case-control studies (RR: 0.69; 95% CI: 0.56 to 0.87, p = 0.001; I² = 58.2%, p _{for heterogeneity} = 0.026), but not in the cohort studies (RR, 0.96; 95% CI: 0.82 to 1.14, p = 0.69; I² = 66.7%, p for heterogeneity = 0.029). In addition, stratified analysis suggested that sample size could be a potential source of heterogeneity.

Conclusions

Results of the current meta-analysis suggest that high intake of whole grains might be inversely associated with a reduced risk of breast cancer, and the inverse association was only observed in case-control but not cohort studies. More large-scale cohort studies are needed to confirm the inverse association observed.

Electronic supplementary material

The online version of this article (10.1186/s12937-018-0394-2) contains supplementary material, which is available to authorized users.

Intake of bean fiber, beans, and grains and reduced risk of hormone receptor-negative breast cancer: the San Francisco Bay Area Breast Cancer Study

High dietary fiber intake has been associated with reduced breast cancer risk, but few studies considered tumor subtypes defined by estrogen receptor (ER) and progesterone receptor (PR) status or included racial/ethnic minority populations who vary in their fiber intake. We analyzed food frequency data from a population-based case-control study, including 2135 breast cancer cases (1070 Hispanics, 493 African Americans, and 572 non-Hispanic Whites (NHWs)) and 2571 controls (1391 Hispanics, 557 African Americans, and 623 NHWs). Odds ratios (OR) and 95% confidence intervals (CI) for breast cancer associated with fiber intake were calculated using unconditional logistic regression. Breast cancer risk associated with high intake (high vs. low quartile) of bean fiber (p-trend = 0.01), total beans (p-trend = 0.03), or total grains (p-trend = 0.05) was reduced by 20%. Inverse associations were strongest for ER-PR- breast cancer, with risk reductions associated with high intake ranging from 28 to 36%. For bean fiber, risk was reduced among foreign-born Hispanics only, who had the highest fiber intake, whereas for grain intake, inverse associations were found among NHWs only. There was no evidence of association with fiber intake from vegetables and fruits or total intake of vegetables and fruits. A high dietary intake of bean fiber and fiber-rich foods such as beans and grains may lower the risk of ER-PR- breast cancer, an aggressive breast cancer subtype for which few risk factors have been identified.

Dietary fibre intake and risk of breast cancer: A systematic review and meta-analysis of epidemiological studies

Current evidence from randomised controlled trials on the effects of dietary fibre intake on breast cancer risk is inconsistent. We conducted a meta-analysis to determine the effectiveness of dietary fibre intake in reducing breast cancer risk. We searched for prospective and case-control studies on dietary fibre intake and breast cancer risk in the English language through March 2016. Twenty-four epidemiologic studies obtained through the PubMed, Embase, Web of Science, and Cochrane Library databases were systematically reviewed. A random-effects model was used to compute the pooled risk estimates by extracting the risk estimate of the highest and lowest reported categories of intake from each study. The meta-analyses showed a 12% decrease in breast cancer risk with dietary fibre intake. The association between dietary fibre intake and breast cancer risk was significant when stratified according to Jadad scores, study types, and menopause status. Dose-response analysis showed that every 10 g/d increment in dietary fibre intake was associated with a 4% reduction in breast cancer risk, and little evidence of publication bias was found. Thus, dietary fibre consumption is significantly associated with a reduced risk of breast cancer, particularly in postmenopausal women.

Tree nut, peanut, and peanut butter intake and risk of postmenopausal breast cancer: The Netherlands Cohort Study

PURPOSE

Nut intake has been associated with reduced mortality and risk of cardiovascular diseases, but there is only limited evidence on cancer. We investigated the relationship between nut intake and risk of postmenopausal breast cancer, and estrogen/progesterone receptor (ER/PR) subtypes.

METHODS

In The Netherlands Cohort Study, 62,573 women aged 55-69 years provided information on dietary and lifestyle habits in 1986. After 20.3 years of follow-up, 2,321 incident breast cancer cases and 1,665 subcohort members were eligible for multivariate case-cohort analyses.

RESULTS

Total nut intake was significantly inversely related to ER negative (ER -) breast cancer risk, with HR 0.55 (95% CI 0.33-0.93) for those consuming at least 10 g nuts/day versus non-consumers (p trend = 0.025). There were no significant inverse associations with ER + or total breast cancer. While there was no variation between PR subtypes, the ER-PR- subtype was also significantly inversely associated with nut intake, with HR 0.53 (95% CI 0.29-0.99), p trend = 0.037. Intake of peanuts and tree nuts separately was also inversely related to ER - breast cancer subtypes, while no associations were found with peanut butter intake.

CONCLUSIONS

Our findings suggest an inverse association between nut intake and ER - breast cancer, and no association with total or hormone receptor-positive subtypes.

Tree nut, peanut, and peanut butter intake and risk of postmenopausal breast cancer: The Netherlands Cohort Study

PURPOSE

Nut intake has been associated with reduced mortality and risk of cardiovascular diseases, but there is only limited evidence on cancer. We investigated the relationship between nut intake and risk of postmenopausal breast cancer, and estrogen/progesterone receptor (ER/PR) subtypes.

METHODS

In The Netherlands Cohort Study, 62,573 women aged 55-69 years provided information on dietary and lifestyle habits in 1986. After 20.3 years of follow-up, 2,321 incident breast cancer cases and 1,665 subcohort members were eligible for multivariate case-cohort analyses.

RESULTS

Total nut intake was significantly inversely related to ER negative (ER -) breast cancer risk, with HR 0.55 (95% CI 0.33-0.93) for those consuming at least 10 g nuts/day versus non-consumers (p trend = 0.025). There were no significant inverse associations with ER + or total breast cancer. While there was no variation between PR subtypes, the ER-PR- subtype was also significantly inversely associated with nut intake, with HR 0.53 (95% CI 0.29-0.99), p trend = 0.037. Intake of peanuts and tree nuts separately was also inversely related to ER - breast cancer subtypes, while no associations were found with peanut butter intake.

CONCLUSIONS

Our findings suggest an inverse association between nut intake and ER - breast cancer, and no association with total or hormone receptor-positive subtypes.

Dietary Protein Sources and Incidence of Breast Cancer: A Dose-Response Meta-Analysis of Prospective Studies

Protein is important to the human body, and different sources of protein may have different effects on the risk of breast cancer. Thus, we conducted a meta-analysis to investigate the association between different dietary protein sources and breast cancer risk. PubMed and several databases were searched until December 2015. Relevant articles were retrieved according to specific searching criteria. Forty-six prospective studies were included. The summary relative risk (RR) for highest versus lowest intake was 1.07 (95% confidence interval (CI) 1.01-1.14, I² = 34.6%) for processed meat, 0.92 (95% CI 0.84-1.00, I² = 0%) for soy food, 0.93 (95% CI 0.85-1.00, I² = 40.1%) for skim milk, and 0.90 (95% CI 0.82-1.00, I² = 0%) for yogurt. Similar conclusions were obtained in dose-response association for each serving increase: total red meat (RR: 1.07; 95% CI 1.01-1.14, I² = 7.1%), fresh red meat (RR: 1.13; 95% CI 1.01-1.26, I² = 56.4%), processed meat (RR: 1.09; 95% CI 1.02-1.17, I² = 11.8%), soy food (RR: 0.91; 95% CI 0.84-1.00, I² = 0%), and skim milk (RR: 0.96; 95% CI 0.92-1.00, I² = 11.9%). There was a null association between poultry, fish, egg, nuts, total milk, and whole milk intake and breast cancer risk. Higher total red meat, fresh red meat, and processed meat intake may be risk factors for breast cancer, whereas higher soy food and skim milk intake may reduce the risk of breast cancer.

Lifetime grain consumption and breast cancer risk

We evaluated individual grain-containing foods and whole and refined grain intake during adolescence, early adulthood, and premenopausal years in relation to breast cancer risk in the Nurses' Health Study II. Grain-containing food intakes were reported on a baseline dietary questionnaire (1991) and every 4 years thereafter. Among 90,516 premenopausal women aged 27-44 years, we prospectively identified 3235 invasive breast cancer cases during follow-up to 2013. 44,263 women reported their diet during high school, and from 1998 to 2013, 1347 breast cancer cases were identified among these women. Cox proportional hazards regression was used to estimate relative risks (RR) and 95 % confidence intervals (95 % CI) of breast cancer for individual, whole and refined grain foods. After adjusting for known breast cancer risk factors, adult intake of whole grain foods was associated with lower premenopausal breast cancer risk (highest vs. lowest quintile: RR 0.82; 95 % CI 0.70-0.97; P trend = 0.03), but not postmenopausal breast cancer. This association was no longer significant after further adjustment for fiber intake. The average of adolescent and early adulthood whole grain food intake was suggestively associated with lower premenopausal breast cancer risk (highest vs lowest quintile: RR 0.74; 95 % CI 0.56-0.99; P trend = 0.09). Total refined grain food intake was not associated with risk of breast cancer. Most individual grain-containing foods were not associated with breast cancer risk. The exceptions were adult brown rice which was associated with lower risk of overall and premenopausal breast cancer (for each 2 servings/week: RR 0.94; 95 % CI 0.89-0.99 and RR 0.91; 95 % CI 0.85-0.99, respectively) and adult white bread intake which was associated with increased overall breast cancer risk (for each 2 servings/week: RR 1.02; 95 % CI 1.01-1.04), as well as breast cancer before and after menopause. Further, pasta intake was inversely associated with overall breast cancer risk. Our results suggest that high whole grain food intake may be associated with lower breast cancer risk before menopause. Fiber in whole grain foods may mediate the association with whole grains.

Fruit and vegetable consumption in adolescence and early adulthood and risk of breast cancer: population based cohort study

OBJECTIVE

To evaluate the association between fruit and vegetable intake during adolescence and early adulthood and risk of breast cancer.

DESIGN

Prospective cohort study.

SETTING

Health professionals in the United States.

PARTICIPANTS

90 476 premenopausal women aged 27-44 from the Nurses' Health Study II who completed a questionnaire on diet in 1991 as well as 44 223 of those women who completed a questionnaire about their diet during adolescence in 1998.

MAIN OUTCOME MEASURE

Incident cases of invasive breast cancer, identified through self report and confirmed by pathology report.

RESULTS

There were 3235 cases of invasive breast cancer during follow-up to 2013. Of these, 1347 cases were among women who completed a questionnaire about their diet during adolescence (ages 13-18). Total fruit consumption during adolescence was associated with a lower risk of breast cancer. The hazard ratio was 0.75 (95% confidence interval 0.62 to 0.90; P=0.01 for trend) for the highest (median intake 2.9 servings/day) versus the lowest (median intake 0.5 serving/day) fifth of intake. The association for fruit intake during adolescence was independent of adult fruit intake. There was no association between risk and total fruit intake in early adulthood and total vegetable intake in either adolescence or early adulthood. Higher early adulthood intake of fruits and vegetables rich in α carotene was associated with lower risk of premenopausal breast cancer. The hazard ratio was 0.82 (0.70 to 0.96) for the highest fifth (median intake 0.5 serving/day) versus the lowest fifth (median intake 0.03 serving/day) intake. The association with adolescent fruit intake was stronger for both estrogen and progesterone receptor negative cancers than estrogen and progesterone receptor positive cancers (P=0.02 for heterogeneity). For individual fruits and vegetables, greater consumption of apple, banana, and grapes during adolescence and oranges and kale during early adulthood was significantly associated with a reduced risk of breast cancer. Fruit juice intake in adolescence or early adulthood was not associated with risk.

CONCLUSION

There is an association between higher fruit intake and lower risk of breast cancer. Food choices during adolescence might be particularly important.

Nut consumption and risk of cancer and type 2 diabetes: a systematic review and meta-analysis

CONTEXT

The identification of foods that can decrease the risk of cancer and type 2 diabetes may be helpful in reducing the burden of these diseases. Although nut consumption has been suggested to have a disease-preventive role, current evidence remains inconsistent.

OBJECTIVE

The aim of this systematic review and meta-analysis was to clarify the association between nut consumption and risk of cancer or type 2 diabetes.

DATA SOURCES

Six databases were searched for relevant studies from the time of database inception to August 2014. Reference lists of relevant review articles were hand searched, and authors were contacted when data were insufficient.

STUDY SELECTION

Eligible studies included epidemiological studies (case-control and cohort) or clinical trials that reported an association between nut consumption and the outcome of type 2 diabetes or specific cancers.

DATA EXTRACTION

Two investigators independently extracted descriptive, quality, and risk data from included studies.

DATA SYNTHESIS

Random-effects meta-analysis was used to pool relative risks from the included studies. The I(2) statistic was used to assess heterogeneity. A total of 36 eligible observational studies, which included 30,708 patients, were identified. The studies had fair methodological quality, and length of follow-up ranged between 4.6 years and 30 years. Comparison of the highest category of nut consumption with the lowest category revealed significant associations between nut consumption and decreased risk of colorectal cancer (3 studies each with separate estimates for males and females, RR 0.76, 95% confidence interval [95%CI] 0.61-0.96), endometrial cancer (2 studies, RR 0.58, 95%CI 0.43-0.79), and pancreatic cancer (1 study, RR 0.68, 95%CI 0.48-0.96). No significant association was found with other cancers or type 2 diabetes. Overall, nut consumption was significantly associated with a reduced risk of cancer incidence (RR 0.85, 95%CI 0.76-0.95).

CONCLUSIONS

Nut consumption may play a role in reducing cancer risk. Additional studies are needed to more accurately assess the relationship between nut consumption and the prevention of individual types of cancer, given the scarcity of available data.

Adolescent dietary fiber, vegetable fat, vegetable protein, and nut intakes and breast cancer risk

The importance of early-life exposures in breast cancer development is increasingly recognized. However, limited research has evaluated the relationship between adolescent diet and subsequent risk of breast cancer and reported inconsistent results. This population-based case-control study investigated the associations of dietary fiber, vegetable protein, vegetable fat, and nuts consumed during adolescence with adult breast cancer risk. Women, ages 25-74 years, who were diagnosed with first primary breast cancer between 2002 and 2003, were identified using the Ontario Cancer Registry. Controls were identified through random-digit dialing and age-frequency matched to cases. Diet at ages 10-15 was assessed with a 55-item food frequency questionnaire among 2,865 cases and 3,299 controls. Logistic regression was performed to estimate odds ratios (ORs) and 95 % confidence intervals (CIs). Inverse associations were found between intakes of dietary fiber, vegetable protein, vegetable fat, and nuts during adolescence and breast cancer risk, which persisted after controlling for adult intakes. The ORs (95 % CI) for the highest versus the lowest quintile of intake were 0.66 (0.55-0.78; P trend < 0.0001) for fiber, 0.80 (0.68-0.95; P trend = 0.01) for vegetable protein, 0.74 (0.63-0.87; P trend = 0.002) for vegetable fat, and 0.76 (0.61-0.95 for ≥1 serving/day vs. <1 serving/month intake; P trend = 0.04) for nuts. The reduced risk for adolescent intakes of fiber, vegetable protein, and nuts was largely limited to postmenopausal women (P interaction ≤ 0.05). Dietary fiber, vegetable protein, vegetable fat, and nuts consumed during adolescence were associated with reduced breast cancer risk.

Adolescent dietary fiber, vegetable fat, vegetable protein, and nut intakes and breast cancer risk

The importance of early-life exposures in breast cancer development is increasingly recognized. However, limited research has evaluated the relationship between adolescent diet and subsequent risk of breast cancer and reported inconsistent results. This population-based case-control study investigated the associations of dietary fiber, vegetable protein, vegetable fat, and nuts consumed during adolescence with adult breast cancer risk. Women, ages 25-74 years, who were diagnosed with first primary breast cancer between 2002 and 2003, were identified using the Ontario Cancer Registry. Controls were identified through random-digit dialing and age-frequency matched to cases. Diet at ages 10-15 was assessed with a 55-item food frequency questionnaire among 2,865 cases and 3,299 controls. Logistic regression was performed to estimate odds ratios (ORs) and 95 % confidence intervals (CIs). Inverse associations were found between intakes of dietary fiber, vegetable protein, vegetable fat, and nuts during adolescence and breast cancer risk, which persisted after controlling for adult intakes. The ORs (95 % CI) for the highest versus the lowest quintile of intake were 0.66 (0.55-0.78; P trend < 0.0001) for fiber, 0.80 (0.68-0.95; P trend = 0.01) for vegetable protein, 0.74 (0.63-0.87; P trend = 0.002) for vegetable fat, and 0.76 (0.61-0.95 for ≥1 serving/day vs. <1 serving/month intake; P trend = 0.04) for nuts. The reduced risk for adolescent intakes of fiber, vegetable protein, and nuts was largely limited to postmenopausal women (P interaction ≤ 0.05). Dietary fiber, vegetable protein, vegetable fat, and nuts consumed during adolescence were associated with reduced breast cancer risk.

Fruits, vegetables and breast cancer risk: a systematic review and meta-analysis of prospective studies

Evidence for an association between fruit and vegetable intake and breast cancer risk is inconclusive. To clarify the association, we conducted a systematic review and meta-analysis of the evidence from prospective studies. We searched PubMed for prospective studies of fruit and vegetable intake and breast cancer risk until April 30, 2011. We included fifteen prospective studies that reported relative risk estimates and 95 % confidence intervals (CIs) of breast cancer associated with fruit and vegetable intake. Random effects models were used to estimate summary relative risks. The summary relative risk (RR) for the highest versus the lowest intake was 0.89 (95 % CI: 0.80-0.99, I (2) = 0 %) for fruits and vegetables combined, 0.92 (95 % CI: 0.86-0.98, I (2) = 9 %) for fruits, and 0.99 (95 % CI: 0.92-1.06, I (2) = 20 %) for vegetables. In dose-response analyses, the summary RR per 200 g/day was 0.96 (95 % CI: 0.93-1.00, I (2) = 2 %) for fruits and vegetables combined, 0.94 (95 % CI: 0.89-1.00, I (2) = 39 %) for fruits, and 1.00 (95 % CI: 0.95-1.06, I (2) = 17 %) for vegetables. In this meta-analysis of prospective studies, high intake of fruits, and fruits and vegetables combined, but not vegetables, is associated with a weak reduction in risk of breast cancer.

Dietary fiber and breast cancer risk: a systematic review and meta-analysis of prospective studies

BACKGROUND

Evidence from case-control studies suggest that dietary fiber may be inversely related to breast cancer risk, but it is unclear if this is supported by prospective data. We conducted a systematic review and meta-analysis of the evidence from prospective studies.

METHODS

PubMed was searched for prospective studies of fiber intake and breast cancer risk until 31st August 2011. Random effects models were used to estimate summary relative risks (RRs).

RESULTS

Sixteen prospective studies were included. The summary RR for the highest versus the lowest intake was 0.93 [95% confidence interval (CI) 0.89-0.98, I(2) = 0%] for dietary fiber, 0.95 (95% CI 0.86-1.06, I(2) = 4%) for fruit fiber, 0.99 (95% CI 0.92-1.07, I(2) = 1%) for vegetable fiber, 0.96 (95% CI 0.90-1.02, I(2) = 5%) for cereal fiber, 0.91 (95% CI 0.84-0.99, I(2) = 7%) for soluble fiber and 0.95 (95% CI 0.89-1.02, I(2) = 0%) for insoluble fiber. The summary RR per 10 g/day of dietary fiber was 0.95 (95% CI 0.91-0.98, I(2) = 0%, P(heterogeneity) = 0.82). In stratified analyses, the inverse association was only observed among studies with a large range (≥13 g/day) or high level of intake (≥25 g/day).

CONCLUSION

In this meta-analysis of prospective studies, there was an inverse association between dietary fiber intake and breast cancer risk.

Dietary fiber intake and risk of breast cancer: a meta-analysis of prospective cohort studies

BACKGROUND

Observational and preclinical studies suggest that dietary fiber intake may reduce the risk of breast cancer, but the results are inconclusive.

OBJECTIVE

We aimed to examine the association between dietary fiber intake and risk of breast cancer by conducting a meta-analysis of prospective cohort studies.

DESIGN

Relevant studies were identified by a PubMed database search through January 2011. Reference lists from retrieved articles were also reviewed. We included prospective cohort studies that reported RRs with 95% CIs for the association between dietary fiber intake and breast cancer risk. Both fixed- and random-effects models were used to calculate the summary risk estimates.

RESULTS

We identified 10 prospective cohort studies of dietary fiber intake and risk of breast cancer involving 16,848 cases and 712,195 participants. The combined RR of breast cancer for the highest compared with the lowest dietary fiber intake was 0.89 (95% CI: 0.83, 0.96), and little evidence of heterogeneity was observed. The association between dietary fiber intake and risk of breast cancer did not significantly differ by geographic region, length of follow-up, or menopausal status of the participants. Omission of any single study had little effect on the combined risk estimate. Dose-response analysis showed that every 10-g/d increment in dietary fiber intake was associated with a significant 7% reduction in breast cancer risk. Little evidence of publication bias was found.

CONCLUSION

This meta-analysis provides evidence of a significant inverse dose-response association between dietary fiber intake and breast cancer risk.

Plasma folate concentrations are positively associated with risk of estrogen receptor beta negative breast cancer in a Swedish nested case control study

Folate's role in breast cancer development is controversial. Not only estrogen receptor (ER) alpha status, but also ERbeta status of tumors may have confounded results from previous epidemiological studies. We aimed to examine associations between plasma folate concentration and postmenopausal breast cancer defined by ER status. This nested case-control study, within the Malmö diet and cancer cohort, included 204 incident breast cancer cases with information on ERalpha and ERbeta status determined by immunochemistry on tissue micro-array sections. Plasma folate concentration was analyzed for the cases and 408 controls (matched on age and blood sample date). Odds ratios (OR) for ER-defined breast cancers in tertiles of plasma folate concentration were calculated with unconditional logistic regression. All tests were 2-sided. Women in the third tertile of plasma folate concentration (> 12 nmol/L) had higher incidence of ERbeta- breast cancer than women in the first tertile (OR: 2.67; 95% CI: 1.44-4.92; P-trend = 0.001). We did not observe significant associations between plasma folate concentration and other breast cancer subgroups defined by ER status. We observed a difference between risks for ERbeta + and ERbeta- cancer (P-heterogeneity = 0.003). Our findings, which indicate a positive association between plasma folate and ERbeta- breast cancer, highlight the importance of taking ERbeta status into consideration in studies of folate and breast cancer. The study contributes knowledge concerning folate's multifaceted role in cancer development. If replicated in other populations, the observations may have implications for public health, particularly regarding folic acid fortification.

Intake of fiber and nuts during adolescence and incidence of proliferative benign breast disease

OBJECTIVE

We examined the association between adolescent fiber intake and proliferative BBD, a marker of increased breast cancer risk, in the Nurses' Health Study II.

METHODS

Among 29,480 women who completed a high school diet questionnaire in 1998, 682 proliferative BBD cases were identified and confirmed by centralized pathology review between 1991 and 2001. Multivariate-adjusted Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

Women in the highest quintile of adolescent fiber intake had a 25% lower risk of proliferative BBD (multivariate HR (95% CI): 0.75 (0.59, 0.96), p-trend = 0.01) than women in the lowest quintile. High school intake of nuts was also related to significantly reduced BBD risk. Women consuming >or=2 servings of nuts/week had a 36% lower risk (multivariate HR (95% CI): 0.64 (0.48, 0.85), p-trend < 0.01) than women consuming <1 serving/month. Results were essentially the same when the analysis was restricted to prospective cases (n = 142) diagnosed after return of the high school diet questionnaire.

CONCLUSIONS

These findings support the hypothesis that dietary intake of fiber and nuts during adolescence influences subsequent risk of breast disease and may suggest a viable means for breast cancer prevention.

Impact of diet on breast cancer risk

PURPOSE OF REVIEW

Breast cancer is the most common female cancer in Western Europe and North America, and becoming an increasing problem in developing countries such as India and China. We review recent studies (published 1 January 2007-31 August 2008) on the impact of diet on breast cancer risk.

RECENT FINDINGS

Recent studies have focused on the controversial association for dietary fat and breast cancer as well as the role of newer aspects such as glycemic index, dietary patterns and diet-gene interactions. Evidence that some of the associations may be modified by oestrogen and progesterone receptor status has been presented. Still, only alcohol intake, being overweight and weight gain have shown consistent and strong positive associations with breast cancer risk. The reasons for the null or weak associations often observed regarding diet and breast cancer might be several. For example, there may be no causal association, or existing associations may be masked by measurement error, timing of dietary exposure and differences according to tumour characteristics or diet-gene interactions.

SUMMARY

Numerous epidemiological studies on diet and breast cancer have been published during our review period. Still, only alcohol intake, being overweight and weight gain have shown consistent and strong positive associations with breast cancer risk.