Construction of a flavonoid database for assessing intake in a population-based sample of women on Long Island, New York

Flavonoids have been hypothesized to reduce cancer risk. Previous epidemiological studies conducted to evaluate this hypothesis have not assessed all flavonoids, including classes that could contribute to intake among Americans, which would result in an underestimation of intake. This misclassification could mask variability among individuals, resulting in attenuated effect estimates for the association between flavonoids and cancer. To augment flavonoid and lignan intake estimates, we developed a database that can be used in conjunction with a food-frequency questionnaire (FFQ). Coupling information derived from the available literature with the U.S. Department of Agriculture databases, we estimated content of 6 flavonoid classes and lignans for 50 food group items. We combined these estimates with responses from a modified Block FFQ that was self-completed in 1996-1997 by a population-based sample of women without breast cancer on Long Island, New York (n = 1,500). Total flavonoid and lignan content of food items ranged from 0 to 129 mg/100 g, and the richest sources were tea, cherries, and grapefruit. Individual intake estimates, from highest to lowest, were flavan-3-ols, flavanones, flavonols, lignans, isoflavones, anthocyanidins, and flavones. Each class of flavonoids and lignans exhibited a wide range of intake levels. This database is useful to quantify flavonoid and lignan intake for other observational studies conducted in the United States that utilize the Block FFQ.     

The Risk of Lung Cancer Related to Dietary Intake of Flavonoids

It has been hypothesized that flavonoids in foods and beverages may reduce cancer risk through antioxidation, inhibition of inflammation, and other antimutagenic and antiproliferative properties. We examined associations between intake of 5 flavonoid subclasses (anthocyanidins, flavan-3-ols, flavones, flavonols, and flavanones) and lung cancer risk in a population-based case-control study in Montreal, Canada (1061 cases and 1425 controls). Flavonoid intake was estimated from a food frequency questionnaire that assessed diet 2 yr prior to diagnosis (cases) or interview (controls). Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression. Overall, total flavonoid intake was not associated with lung cancer risk, the effect being similar regardless of sex and smoking level. However, low flavonoid intake from food, but not from beverages, was associated with an increased risk. The adjusted ORs (95% CIs) comparing the highest vs. the lowest quartiles of intake were 0.63 (0.47–0.85) for total flavonoids, 0.82 (0.61–1.11) for anthocyanidins, 0.67 (0.50–0.90) for flavan-3-ols, 0.68 (0.50–0.93) for flavones, 0.62 (0.45–0.84) for flavonols, and 0.70 (0.53–0.94) for flavanones. An inverse association with total flavone and flavanone intake was observed for squamous cell carcinoma but not adenocarcinoma. In conclusion, low flavonoid intake from food may increase lung cancer risk.     

Fruits, vegetables, soy foods and breast cancer in pre- and postmenopausal Korean women: a case-control study

We carried out a case-control study to examine the relationship between fruits, vegetables, and soy foods intake with breast cancer risk in Korean women. Incident cases (n = 359) were identified through cancer biopsies and hospital-based controls (n = 708) were selected in the same hospitals. Subjects were asked to indicate usual dietary habits, which were assessed using a semi-quantitative food frequency questionnaire (98 items). Odds ratio (OR) and 95% confidence intervals (95% CI) were calculated by unconditional logistic regression after adjustment for additional confounding factors according to the menopausal status. High grape intake showed an inverse association of breast cancer in postmenopausal women (OR = 0.59, 95% CI = 0.35-0.95; p for trend = 0.05). High tomato intake was associated with reduced breast cancer risk in premenopausal women (OR = 0.59, 95% CI = 0.38-0.89, p for trend = 0.04). In postmenopausal women, green pepper intake showed an inverse association of breast cancer risk (OR = 0.60, 95% CI = 0.43-0.96, p for trend = 0.03). High soybean intake showed an inverse association of breast cancer in postmenopausal women (OR = 0.61, 95% CI = 0.34-0.89, p for trend = 0.02). Our study suggests that high intake of some fruits, vegetables, and soybeans may be associated with a reduced breast cancer risk.     

The risk of breast cancer associated with dietary lignans differs by CYP17 genotype in women

Lignans are plant compounds metabolized in the gut to produce the phytoestrogens enterolactone and enterodiol. Reduced breast cancer risks associated with higher urinary lignan excretion may be related to competitive inhibition of endogenous estrogens. Evidence exists that associations with reproductive risk factors for breast cancer differ according to cytochrome P450c17alpha (CYP17) genotype. Genetic variability in estrogen metabolism could affect lignan metabolism thereby modifying risk associations. We examined breast cancer risk, dietary lignans and CYP17 genotype among 207 women with primary, incident, histologically confirmed breast cancer and 188 controls frequency matched to cases by age and county of residence. Self-reported frequency of intake of 170 foods and beverages during the 2 y before the interview and other relevant data were collected by detailed in-person interviews. Dietary lignan intake was expressed as the sum of enterolactone and enterodiol production from foods. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by unconditional logistic regression, adjusting for age, education and other breast cancer risk factors. Women in the highest tertile of dietary lignans tended to have reduced breast cancer risk (OR 0.45, 95% CI 0.20-1.01 and OR 0.59, 95% CI 0.28-1.27, pre- and postmenopausal women, respectively). Substantially reduced risks in the highest tertile of lignans were observed for premenopausal women with at least one A2 allele (OR 0.12, 95% CI 0.03-0.50). Our results suggest that CYP17 genotype may be important in modifying the effect on breast cancer risk of exogenous estrogens, particularly for premenopausal women.     

Dietary flavan-3-ols intake and metabolic syndrome risk in Korean adults

Flavan-3-ols are a subclass of flavonoids found in a variety of foods including teas. The effects of flavan-3-ols on the risk of metabolic syndrome (MetS) have been investigated, generally focusing on tea catechins or individual flavan-3-ol rich foods, but there is little information on dietary flavan-3-ols intake and risk of MetS in population-based studies. In this cross-sectional study, we examined the association between dietary flavan-3-ols intake and the risk of MetS in Korean adults. Subjects comprised 1,827 men and 2,918 women aged 20-69 years whose data was included in the 2008 Korean National Health and Nutrition Examination Survey. This survey was conducted between January 2008 and December 2008. Total flavan-3-ols intakes were calculated from 24-hour dietary recalls using a flavonoids database. Thirty percent of the male subjects and 24% of the female subjects were reported as having MetS. In the female subjects, flavan3-ols intake was inversely associated with the risk of MetS after adjusting for potential confounders (5th vs. 1st quintile, OR = 0.64, 95% CI = 0.45-0.91, P for trend = 0.384). The main food source of flavan-3-ols was green tea followed by apples and grapes. Among MetS components, flavan3-ols intake was inversely associated with the risk of high blood pressure after adjusting for potential confounders (5th vs. 1st quintile, OR = 0.64, 95% CI = 0.45-0.90, P for trend = 0.005). No significant association between flavan-3-ols intake and risk of MetS was found in the male subjects. After stratified analysis by obesity (BMI ≥ 25 or BMI < 25), however, flavan3-ols intake was inversely related to the risk of hypertension in non-obese men. These results suggest that dietary flavan-3-ols intake may have beneficial effects on MetS risk by reducing the risk of hypertension. The effects of flavan-3-ols intake dependent on obesity need further investigation.     

The association between dietary lignans, phytoestrogen-rich foods, and fiber intake and postmenopausal breast cancer risk: a German case-control study

Phytoestrogens are structurally similar to estrogens and may affect breast cancer risk by mimicking estrogenic/antiestrogenic properties. In Western societies, whole grains and possibly soy foods are rich sources of phytoestrogens. A population-based case-control study in German postmenopausal women was used to evaluate the association of phytoestrogen-rich foods and dietary lignans with breast cancer risk. Dietary data were collected from 2,884 cases and 5,509 controls using a validated food-frequency questionnaire, which included additional questions phytoestrogen-rich foods. Associations were assessed using conditional logistic regression. All analyses were adjusted for relevant risk and confounding factors. Polytomous logistic regression analysis was performed to evaluate the associations by estrogen receptor (ER) status. High and low consumption of soybeans as well as of sunflower and pumpkin seeds were associated with significantly reduced breast cancer risk compared to no consumption (OR = 0.83, 95% CI = 0.70-0.97; and OR = 0.66, 95% CI = 0.77-0.97, respectively). The observed associations were not differential by ER status. No statistically significant associations were found for dietary intake of plant lignans, fiber, or the calculated enterolignans. Our results provide evidence for a reduced postmenopausal breast cancer risk associated with increased consumption of sunflower and pumpkin seeds and soybeans.     

Body size changes in relation to postmenopausal breast cancer among women on Long Island, New York

To examine effects of body size change on postmenopausal breast cancer, the authors conducted a population-based case-control study among 990 cases and 1,006 controls participating in the Long Island Breast Cancer Study Project in 1996-1997. Women who had gained more than 15 kg (33 pounds) since age 20 years were at a 1.6-fold increased risk of breast cancer (95% confidence interval (CI): 1.11, 2.26) relative to their counterparts with stable (+/-3 kg) weight. Subjects who had gained more than 11 kg (24 pounds) during the peri- and postmenopausal years (since age 50 years) had 1.62 times the risk of breast cancer of those whose weight remained unchanged during this time period. This effect of peri- and postmenopausal body size gain was present only among never users of hormone replacement therapy (odds ratio (OR) = 2.02 (95% CI: 1.35, 3.02) as opposed to 0.81 (95% CI: 0.43, 1.53) for ever users; multiplicative interaction: p < 0.01) and was more pronounced among women with estrogen receptor-positive/progesterone receptor-positive breast cancer (OR = 2.17, 95% CI: 1.38, 3.42). Weight loss over the lifetime was associated with decreased risk of postmenopausal breast cancer (OR = 0.55, 95% CI: 0.32, 0.96). These results add to the literature by focusing on the perimenopausal weight trajectory and support efforts urging women to avoid weight gain as they age.     

Flavonoid intake in relation to lung cancer risk: case-control study among women in Greece

We have examined the role of three classes of flavonoids that are relatively common in the Greek diet (flavanones, flavan-3-ols, and flavonols) in the etiology of lung cancer using data from a case-control study among women, which was undertaken in Athens, Greece, in the late 1980s. Study subjects were 154 women with lung cancer and 145 control women with orthopedic conditions. Women reported their life-long smoking histories and average frequency of consumption, before onset of present disease, of 47 food items or beverages that collectively covered >80% of the intake of each of the energy-providing nutrients. Intakes of flavonoids were calculated using the recently published U.S. Department of Agriculture database. The data were modeled through logistic regression, controlling for energy intake and smoking. There was no indication that intake of any of the studied flavonoid categories reduces the risk of lung cancer; indeed, for flavonols there was an unexpected positive association. Thus, our study does not indicate a protective effect of flavanones, flavan-3-ols, or flavonols on lung cancer risk and indicates that the factors responsible for the protective effect of vegetables and fruits against the risk of this cancer are unlikely to belong to these flavonoid categories.     

Flavonoids and prostate cancer risk: a study in Italy

Flavonoids have been associated with a reduced risk of lung, digestive tract, and certain hormone-related cancers. With reference to prostate cancer, a few epidemiological studies have found an inverse relation with intake of isoflavones, flavonols, and flavones, although the evidence remains limited and inconsistent. The role of six principal classes of flavonoids on prostate cancer was investigated using data from a multicentric case-control study conducted between 1991 and 2002 in Italy. This included 1,294 incident, histologically confirmed carcinomas of the prostate and 1,451 controls admitted to the same hospitals as cases for a wide spectrum of acute, non-neoplastic conditions. The patients' usual diet was assessed using a validated and reproducible food-frequency questionnaire; food and beverage content of six major classes of flavonoids was obtained from the U.S. Department of Agriculture. No association between prostate cancer risk was found with any of the flavonoids analyzed: the multivariate odds ratios for the highest versus the lowest quintile of intake were 0.96 (95% confidence interval, CI = 0.75-1.23) for flavanones, 1.3 (95% CI = 1.01-1.69) for flavan-3-ols, 1.23 (95% CI = 0.95-1.61) for flavonols, 1.09 (95% CI = 0.85-1.40) for flavonols, 1.18 (95% CI = 0.91-1.53) for anthocyanidins, 0.98 (95% CI = 0.76-1.26) for isoflavones, and 1.20 (95% CI = 0.92-1.58) for total flavonoids, all nonstatistically significant. Thus, the results of the present study do not support a protective effect of flavonoids on prostate cancer in this Italian population, characterized by a high intake of flavonoid-containing foods (except isoflavone-rich foods).     

Cooked meat and risk of breast cancer--lifetime versus recent dietary intake

BACKGROUND: Polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs) are carcinogens formed in or on the surface of well-done meat, cooked at high temperature. METHODS: We estimated breast cancer risk in relation to intake of cooked meat in a population-based, case-control study (1508 cases and 1556 controls) conducted in Long Island, NY from 1996 to 1997. Lifetime intakes of grilled or barbecued and smoked meats were derived from the interviewer-administered questionnaire data. Dietary intakes of PAH and HCA were derived from the self-administered modified Block food frequency questionnaire of intake 1 year before reference date. Unconditional logistic regression was used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Modest increased risk was observed among postmenopausal, but not premenopausal, women consuming the most grilled or barbecued and smoked meats over the life course (OR = 1.47; CI = 1.12-1.92 for highest vs. lowest tertile of intake). Postmenopausal women with low fruit and vegetable intake, but high lifetime intake of grilled or barbecued and smoked meats, had a higher OR of 1.74 (CI = 1.20-2.50). No associations were observed with the food frequency questionnaire-derived intake measures of PAHs and HCAs, with the possible exception of benzo(alpha)pyrene from meat among postmenopausal women whose tumors were positive for both estrogen receptors and progesterone receptors (OR = 1.47; CI = 0.99-2.19). CONCLUSIONS: These results support the accumulating evidence that consumption of meats cooked by methods that promote carcinogen formation may increase risk of postmenopausal breast cancer.     

Cruciferous vegetables, the GSTP1 Ile105Val genetic polymorphism, and breast cancer risk

BACKGROUND: Cruciferous vegetables are the primary source of isothiocyanates and other glucosinolate derivatives that are known to induce phase II detoxifying enzymes, including glutathione S-transferases (GSTs). OBJECTIVE: We investigated the independent and combined effects of cruciferous vegetable intake and the GSTP1 Ile(105)Val genetic polymorphism on breast cancer risk. DESIGN: Analyses included 3035 cases and 3037 population controls who were participating in the Shanghai Breast Cancer Study and for whom diet and genetic data were complete (87% of cases and 85% of controls). RESULTS: With the use of multivariate logistic regression, the GSTP1 Val/Val genotype was significantly associated with greater breast cancer risk (OR = 1.50; 95% CI: 1.12, 1.99). The association was significantly greater in premenopausal women (OR = 1.69; 95% CI: 1.17, 2.43) than in postmenopausal women (OR = 1.20; 95% CI: 0.74, 1.92). Total cruciferous vegetable intake was not significantly associated with breast cancer risk, although subjects reporting greater turnip (P for trend < 0.001) and Chinese cabbage (P for trend = 0.049) intakes had a significantly lower postmenopausal breast cancer risk. Women with the GSTP1 Val/Val genotype and low cruciferous vegetable intake had a breast cancer risk 1.74-fold (95% CI: 1.13, 2.67) that of women with the Ile/Ile or Ile/Val genotype. This effect of low cruciferous vegetable intake and the Val/Val genotype was seen predominantly among premenopausal women (OR = 2.08; 95% CI = 1.20, 3.59). CONCLUSIONS: Cruciferous vegetable intake consistent with high isothiocyanate exposure may reduce breast cancer risk. Cruciferous vegetable intake also may ameliorate the effects of the GSTP1 genotype.     

Dietary intake of soy protein and tofu in association with breast cancer risk based on a case-control study

Soy food and its constituents may protect against breast cancer, but the association between soy intake and decreased breast cancer risk is inconsistent. We evaluated the relationship between breast cancer risk and the dietary intake of soy protein as measured by total soy food and tofu intake. Histologically confirmed cases (n = 362) were matched to controls by age (within 2 yr) and menopausal status. High soy protein intake was associated with reduced breast cancer risk in analyses adjusted for potential confounders including dietary factors among premenopausal women (odds ratio [OR] = 0.39 in the highest quintile, 95% confidence interval [CI] = 0.22-0.93, P for trend = 0.03) and postmenopausal women (OR = 0.22, 95% CI = 0.06-0.88, P for trend = 0.16). We also found an inverse association between total tofu intake and breast cancer risk among premenopausal women (for total tofu intake, OR = 0.23 in the highest quintile, 95% CI = 0.11-0.48, P for trend < 0.01; for at least 1 serving of tofu as the main ingredient per day, OR = 0.26, 95% CI = 0.13-0.55, P for trend < 0.01). We concluded that increased regular soy food intake at a level equivalent to traditional Korean consumption levels may be associated with a reduced risk of breast cancer, and this effect is more pronounced in premenopausal women.     

The intake of flavonoids and carotid atherosclerosis: the Kuopio Ischaemic Heart Disease Risk Factor Study

The role of flavonoids in CVD is still unclear. In this cross-sectional study we assessed the relation between the intakes of twenty-six flavonoids from five subclasses: flavonols, flavones, flavanones, flavan-3-ols and anthocyanidins, and the mean common carotid artery intima-media thickness (CCA-IMT). The study population consisted of 1380 middle-aged eastern Finnish men for whom the mean CCA-IMT examinations were carried out as a part of the prospective population-based Kuopio Ischaemic Heart Disease Risk Factor Study (KIHD). The mean intake of flavonoids was 128.5 (sd 206.7) mg/d and the mean CCA-IMT was 0.78 (sd 0.17) mm. In the lowest quartile of total flavonoid intake the non-adjusted mean CCA-IMT was 0.79 (sd 0.19) mm, while the mean CCA-IMT was 0.76 (sd 0.15) in the highest quartile (P < 0.001). After adjustment for age, variables related to CCA-IMT measurement, history of atherosclerosis, smoking, BMI, diabetes, systolic blood pressure, serum HDL- and LDL-cholesterol, VO2 max, and intakes of alcohol, SFA, folate, vitamins C and E, the total flavonoid intake was inversely associated with the mean CCA-IMT (P = 0.018). Out of different flavonoid subclasses, flavan-3-ols were inversely associated with CCA-IMT (P = 0.025) after statistical adjustment. There was a trend for an inverse association between intake of flavonols and mean CCA-IMT (P = 0.055). We conclude that high intake of flavonoids is associated with decreased carotid atherosclerosis in middle-aged Finnish men.     

Flavonol and flavone intakes in US health professionals

OBJECTIVE: To determine flavonoid content of US foods, mean individual intakes, major food sources, and associations with other nutrients. SUBJECTS: US men (n = 37,886) and women (n = 78,886) who completed a semiquantitative food frequency questionnaire in 1990. DESIGN: Men and women completed a questionnaire that listed 132 items, including onions as a garnish and as a vegetable, rings, or soup. Foods known to be important sources of flavonols (quercetin, myricetin, and kaempferol) and flavones (luteolin and apigenin) were analyzed biochemically. The database contained values from the analyzed foods, previously published values from Dutch foods, and imputed values. STATISTICS: Means and standard deviations, contributions of foods to summed intake of each flavonoid, and Pearson correlation coefficients were calculated. RESULTS: Of the flavonols and flavones studied, quercetin contributed 73% in women and 76% in men. The mean flavonol and flavone intake was approximately 20 to 22 mg per day. Onions, tea, and apples contained the highest amounts of flavonols and flavones. Correlations between the intakes of flavonols and flavones and intakes of beta carotene, vitamin E, vitamin C, folic acid, and dietary fiber did not exceed 0.35. CONCLUSION: Although flavonols and flavones are subgroups of flavonoids hypothesized to be associated with reduced risk of coronary heart disease, data on flavonoid intake has been limited due to the lack of food composition data. Nutrition professionals can use these and other published data to estimate intake of flavonoids in their populations. This work should facilitate the investigation of this class of dietary antioxidants as a contributor to disease prevention.     

Intake of specific carotenoids and essential fatty acids and breast cancer risk in Montreal, Canada

BACKGROUND: Evidence from previous investigations into the possible role of dietary and serum carotenoid concentrations in the etiology of breast cancer is inconsistent. No study has examined the combined effect of carotenoids and essential fatty acids on the risk of breast cancer. OBJECTIVE: The objective was to assess the possible association between specific and total carotenoids and breast cancer risk and to evaluate the effect modification by diet-related fatty acids and lifestyle factors in the development of breast cancer. DESIGN: A population-based case-control study involving 414 incident cases and 429 controls was conducted in French Canadians in Montreal. Dietary intake was estimated with the use of a validated food-frequency questionnaire in face-to-face interviews. RESULTS: No significant association was apparent between any of the individual or total carotenoids and the risk of breast cancer after adjustment for major underlying determinants of breast cancer. In premenopausal women who ever smoked, an increased risk was related to alpha-carotene [odds ratio (OR) for the upper relative to the lowest quartiles of intake: 2.40; 95% CI: 0.90, 6.41; P for trend = 0.046]. Conversely, a reduced risk was related to beta-carotene (OR: 0.57; 95% CI: 0.26, 1.24; P for trend = 0.05) in women who never used hormone replacement therapy. In postmenopausal women, total carotenoids were positively associated with breast cancer risk in those with a high arachidonic acid intake (OR: 1.92; 95% CI: 0.93, 3.94; P = 0.028 for trend) and inversely associated in those with a high docosahexaenoic acid intake (OR: 0.52; 95% CI: 0.25, 1.07; P for trend = 0.054). CONCLUSION: These findings suggest that the combined high intake of total carotenoids and docosahexaenoic acid may reduce the risk of breast cancer.     

Case-control study of lifetime physical activity and breast cancer risk

A population-based case-control study of 1,233 incident breast cancer cases and 1,237 controls was conducted in Alberta, Canada, in 1995-1997 to examine the effect of lifetime physical activity patterns on breast cancer risk. No associations between physical activity and breast cancer were found for premenopausal women. For postmenopausal women in the highest quartile (> or =161 metabolic equivalent (MET)-hours/week per year) versus the lowest quartile (<104.8 MET-hours/week per year) of lifetime total physical activity, the adjusted odds ratio was 0.70 (95% confidence interval (CI): 0.52, 0.94). When the risks associated with each type of activity were examined for postmenopausal women, household and occupational activity conferred the largest risk reductions (odds ratio (OR) = 0.57, 95% CI: 0.41, 0.79 and OR = 0.59, 95% CI: 0.44, 0.81, respectively, for highest vs. lowest quartiles of activity), while recreational activity was not associated with any risk reductions. For postmenopausal women, the authors found stronger risk reductions for those who were also nonsmokers (OR = 0.64, 95% CI: 0.46, 0.88), non-alcohol-drinkers (OR = 0.39, 95% CI: 0.11, 0.77), or nulliparous (OR = 0.22, 95% CI: 0.07, 0.70) when they compared the highest with the lowest quartile of lifetime total physical activity. This study provides evidence that lifetime total activity reduces risk of postmenopausal breast cancer.     

Age and menopausal effects of hormonal birth control and hormone replacement therapy in relation to breast cancer risk

It is unclear whether breast cancer risk varies by age and menopausal status in relation to use of hormonal birth control (HBC) and hormone replacement therapy (HRT), taken singly or cumulatively. The authors utilized data from 1,478 cases and 1,493 controls aged 20-98 years with known menopausal status, who had participated in a population-based, case-control study conducted on Long Island during 1996-1997. Exogenous hormone use over the lifecourse was assessed by use of memory aids. The authors examined associations among women in these subgroups: premenopausal (n = 968), postmenopausal <65 years (n = 1,045), and postmenopausal > or = 65 years (n = 958). Among premenopausal women, risk was increased for ever use of HBC (odds ratio (OR) = 1.37, 95% confidence interval (CI): 1.04, 1.81) or HRT (OR = 1.81, 95% CI: 1.17, 2.81) and was pronounced among women reporting use of both HBC and HRT (OR = 2.59, 95% CI: 1.50, 4.46), long-term HRT use (OR = 3.93, 95% CI: 1.43, 10.84), or estrogen-plus-progestin therapy (OR = 3.51, 95% CI: 1.45, 8.49). There was no effect of ever HBC use among postmenopausal women aged less than 65 years, but risk was modestly elevated for more than 5 years of HRT use (OR = 1.41, 95% CI: 1.00, 1.99). Among postmenopausal women aged 65 years or more, odds ratios for HBC or HRT use were around the null. These results emphasize that timing of exogenous hormone use is important. Women who used these hormones before menopause had elevated risks, but the harmful effects began to decline with age after menopause.     

Dietary Intake of Soy Protein and Tofu in Association With Breast Cancer Risk Based on a Case-Control Study

Soy food and its constituents may protect against breast cancer, but the association between soy intake and decreased breast cancer risk is inconsistent. We evaluated the relationship between breast cancer risk and the dietary intake of soy protein as measured by total soy food and tofu intake. Histologically confirmed cases ( n = 362) were matched to controls by age (within 2 yr) and menopausal status. High soy protein intake was associated with reduced breast cancer risk in analyses adjusted for potential confounders including dietary factors among premenopausal women (odds ratio [OR] = 0.39 in the highest quintile, 95% confidence interval [CI] = 0.22–0.93, P for trend = 0.03) and postmenopausal women (OR = 0.22, 95% CI = 0.06–0.88, P for trend = 0.16). We also found an inverse association between total tofu intake and breast cancer risk among premenopausal women (for total tofu intake, OR = 0.23 in the highest quintile, 95% CI = 0.11–0.48, P for trend < 0.01; for at least 1 serving of tofu as the main ingredient per day, OR = 0.26, 95% CI = 0.13–0.55, P for trend < 0.01). We concluded that increased regular soy food intake at a level equivalent to traditional Korean consumption levels may be associated with a reduced risk of breast cancer, and this effect is more pronounced in premenopausal women.     

Flavonoids and cancer prevention: a review of the evidence

The objective of this work is to review data from epidemiological and preclinical studies addressing the potential benefits of diets based on flavonoids for cancer prevention. Flavonoids are subdivided into subclasses including flavonols, flavones, flavanones, flavan-3-ols, anthocyanidins, and isoflavones. Epidemiological studies suggest dietary intake of flavonoids may reduce the risk of tumors of the breast, colon, lung, prostate, and pancreas. However, some studies have reported inconclusive or even harmful associations. A major challenge in the interpretation of epidemiological studies is that most of the data originate from case-control studies and retrospective acquisition of flavonoid intake. Differences in agricultural, sociodemographics, and lifestyle factors contribute to the heterogeneity in the intake of flavonoids among populations residing in the United States, Europe, and Asia. Dose and timing of exposure may influence the anticancer response to flavonoid-rich diets. A limited number of intervention trials of flavonoids have documented cancer preventative effects. Proposed anticancer mechanisms for flavonoids are inhibition of proliferation, inflammation, invasion, metastasis, and activation of apoptosis. Prospective studies with larger sample sizes are needed to develop biomarkers of flavonoid intake and effect. Mechanistic studies are needed to ascertain how flavonoid-rich diets influence gene regulation for cancer prevention.     

酒精摄入与女性乳腺癌发病风险的Meta分析

目的 探讨酒精摄入与女性乳腺癌发病风险的关联性。方法 通过Stata 12.0软件对国内外发表的有关酒精摄入与女性乳腺癌发病风险的队列研究和病例对照研究进行Meta分析。结果 共纳入16项病例对照研究和15项队列研究,包括50 519例患者和973 216例对照者。病例对照研究Meta分析提示,酒精暴露可明显增加女性个体发生乳腺癌的风险,合并OR值为1.18,95％置信区间为1.05～1.32;以绝经状态为亚组的Meta分析提示,酒精暴露可增加绝经后女性个体发生乳腺癌的风险,合并OR值为1.26,95％置信区间为1.08～1.46。队列研究Meta分析提示,有酒精暴露者女性乳腺癌的发生率是非饮酒者的1.1倍,合并RR值为1.10,95％置信区间为1.06～1.15;以绝经状态为亚组的Meta分析提示,有酒精暴露的绝经后女性乳腺癌的发生率是非饮酒者的1.1倍,合并RR值为1.14,95％置信区间为1.10～1.19。结论 酒精摄入可显著提高女性尤其绝经后乳腺癌的发病风险。