Empirically derived dietary patterns and risk of postmenopausal breast cancer in a large prospective cohort study

BACKGROUND: Inconsistent associations have been reported between diet and breast cancer. OBJECTIVE: We prospectively examined the association between dietary patterns and postmenopausal breast cancer risk in a US-wide cohort study. DESIGN: Data were analyzed from 40 559 women who completed a self-administered 61-item Block food-frequency questionnaire in the Breast Cancer Detection Demonstration Project, 1987-1998; 1868 of those women developed breast cancer. Dietary patterns were defined by using principal components factor analysis. Cox proportional hazard regression was used to assess breast cancer risk. RESULTS: Three major dietary patterns emerged: vegetable-fish/poultry-fruit, beef/pork-starch, and traditional southern. The vegetable-fish/poultry-fruit pattern was associated with higher education than were the other patterns, but was similar in nutrient intake to the traditional southern pattern. After adjustment for confounders, there was no significant association between the vegetable-fish/poultry-fruit and beef/pork-starch patterns and breast cancer. The traditional southern pattern, however, was associated with a nonsignificantly reduced breast cancer risk among all cases (in situ and invasive) that was significant for invasive breast cancer (relative hazard = 0.78; 95% CI = 0.65, 0.95; P for trend = 0.003). This diet was also associated with a reduced risk in women without a family history of breast cancer (P = 0.05), who were underweight or normal weight [body mass index (in kg/m(2)) < 25; P = 0.02], or who had tumors positive for estrogen receptor (P = 0.01) or progesterone receptor (P = 0.003). Foods in the traditional southern pattern associated with reduced breast cancer risk were legumes, low mayonnaise-salad dressing intake, and possibly cabbage. CONCLUSIONS: The traditional southern diet or its components are associated with a reduced risk of invasive breast cancer in postmenopausal women.     

Left-handedness in relation to breast cancer risk in postmenopausal women

Breast cancer risk may be influenced by intrauterine exposure to steroid hormones. We evaluated left-handedness, a marker of intrauterine hormone exposure, in relation to breast cancer risk in our population-based, case-control study. Case women 50-79 years of age with a first diagnosis of invasive breast cancer were ascertained through statewide cancer registries in Wisconsin, Massachusetts, and New Hampshire. Control women were identified in each state through lists of licensed drivers (for ages 50-64) and Medicare beneficiaries (for ages 65-79), and selected at random to correspond with the age distribution of case women. Exposure information, including handedness, was obtained through a telephone interview. Our results indicated a modest association between left-handedness and breast cancer risk (OR = 1.42; 95% CI = 1.10-1.83). The effect of left-handedness was modified by age; we observed the greatest risk ratio in the oldest age group. Left-handedness was not associated with breast tumor laterality. Our results are consistent with the hypothesis that intrauterine hormone exposures play a role in the development of breast cancer.     

Inverse association between dietary and serum conjugated linoleic acid and risk of breast cancer in postmenopausal women

Conjugated linoleic acid (CLA) is anticarcinogenic in experimental animal studies. We studied dietary and serum CLA in Finnish patients with breast cancer in 1992-1995. Participants were consecutive women with breast cancer (68 premenopausal and 127 postmenopausal) and population-based control women (75 premenopausal and 133 postmenopausal), matched for age and area of residence. Diet was assessed by a validated food frequency questionnaire and the fatty acid composition of serum by gas-liquid chromatography. In postmenopausal women, dietary CLA, serum CLA, myristic acid, and trans-vaccenic acid were significantly lower in cases than in controls. The odds ratio for breast cancer in the highest quintile vs. the lowest was 0.4 [95% confidence interval (CI) = 0.2-0.9]for CLA, 0.3 (95% CI = 0.1-0.7) for myristic acid, and 0.3 (95% CI = 0.1-0.7) for trans-vaccenic acid in serum. The odds ratios remained similar after adjustment for known risk factors of breast cancer. A diet composed of CLA-rich foods, particularly cheese, may protect against breast cancer in postmenopausal women, but it is impossible to assess the independent effects of CLA in this study. The findings may be of relevance for food production, inasmuch as it is possible to increase CLA and its precursor trans-vaccenic acid in foods by modifying the feeding of ruminants.     

Use of electric blankets and risk of postmenopausal breast cancer

Chronic exposure to 60-Hz electromagnetic fields has been hypothesized to increase breast cancer risk by suppressing the normal nocturnal rise in pineal melatonin. From 1987 to 1989 in western New York the authors investigated the use of electric blankets as a risk factor for breast cancer in a case-control study of postmenopausal women aged 41-85 years. A study population of 382 cases and 439 randomly selected community controls was queried regarding use in the previous 10 years, the frequency of use by season, and the mode of use. After adjusting for age and education, the odds ratio (OR) for use of an electric blanket in the past 10 years (33% of cases, 35% of controls) was 0.89 (95% confidence interval (95% CI) 0.66-1.19), and the risk did not differ in a dose-response fashion by the number of years used. The risk associated with daily use relative to nonuse was 0.97 (95% CI 0.70-1.35). Use sometimes to warm the bed and sometimes throughout the night was not associated with risk (OR = 0.64, 95% CI 0.40-1.05). The risk of breast cancer among those who used the blanket continuously throughout the night was 1.31 (95% CI 0.88-1.95). Those who reported daily use in season, continuously throughout the night for the past 10 years did not have significantly elevated risk (OR = 1.25, 95% CI 0.73-2.16). Adjustment for the Quetelet index and reproductive risk factors did not alter the results. These findings do not support the hypothesis that electric blanket use is associated with an increased risk for breast cancer. The slightly elevated estimate of risk for the most frequent electric blanket users and the potential public health significance of electromagnetic field exposure suggest that further inquiries be undertaken.     

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.     

Bone mineral density and breast cancer risk in postmenopausal women

Two recent studies have shown a woman's bone mineral density (BMD) (a composite measure of exposure to many different factors throughout one's lifetime) predicts breast cancer. In a prospective cohort study, we examined whether hip BMD was associated with breast cancer risk among 8203 postmenopausal women. During an average follow-up of 3.7 years, 131 incident breast cancer cases (102 invasive) were identified. Cox proportional hazards models were used to obtain estimates of the relative risk of breast cancer. Our results demonstrate an increase in breast cancer risk among women with higher BMD. Independent of age, geographic area, and body mass index, relative to the lowest BMD quartile the risk of breast cancer (95% confidence interval) by increasing quartile was 1.9 (1.1, 3.2), 1.5 (0.8, 2.6), and 1.5 (0.8, 2.7), respectively. An examination of other factors important in determining BMD may help explain the positive association between BMD and breast cancer.     

Adherence to the dietary approaches to stop hypertension (DASH) dietary pattern and mental health in Iranian university students

Examining the association between adherence to the dietary approaches to stop hypertension (DASH) dietary pattern and mental health in Iranian university students. This cross-sectional study was conducted among 240 university students (mean age 21.5 years; 86.7% female). Mental health was evaluated using validated Persian versions of the 12-item general health questionnaire (GHQ-12) and the 21-item depression, anxiety, and stress scale (DASS-21). The lower the subjects’ scores on these questionnaires, the better their mental health. Usual past-year dietary intakes were assessed by a validated 168-item semi-quantitative food frequency questionnaire. The DASH score was computed based on energy-adjusted intakes of eight major dietary components emphasized or minimized in the DASH pattern. The higher the DASH score of a subject, the greater his/her adherence to the DASH pattern. The Pearson’s correlation coefficients of DASH score with GHQ-12 total score, DASS-21 total score, and DASS-21 depression, anxiety, and stress subscale scores were − 0.431, − 0.441, − 0.434, − 0.325, and − 0.408, respectively (all P < 0.001). Compared to those in the lowest tertile, subjects in the highest tertile of DASH score had lower means of GHQ-12 total score (mean difference − 4.6; P < 0.001), DASS-21 total score (mean difference − 9.1; P < 0.001), and DASS-21 depression, anxiety, and stress subscale scores (mean differences for depression, anxiety, and stress − 3.6, − 2.4, and − 3.2, respectively; all P < 0.001). The findings indicate that greater adherence to the DASH dietary pattern is associated with better mental health in Iranian university students. However, prospective studies of sufficient methodological quality are needed to confirm these findings.     

A rationale for dietary intervention in the treatment of postmenopausal breast cancer patients

A rationale is given for the use of a low‐fat diet as a form of adjuvant therapy for postmenopausal breast cancer patients. The rationale is based on both epidemiological and experimental evidence, accrued over the past 40 years, suggesting that dietary fat is an important determinant of both breast cancer risk and probability of survival after surgery. A randomized prospective clinical trial would provide the most direct and feasible experimental mechanism for testing the hypothesis that decreasing the consumption of dietary fat will increase the disease‐free interval and/or the 5‐year survival rates of postmenopausal breast cancer patients.     

Folate intake, alcohol and risk of breast cancer among postmenopausal women in Denmark

OBJECTIVE: There is consistent evidence that alcohol increases the risk of breast cancer. It has been suggested that the increased risk associated with alcohol intake may be reduced by adequate intake of folate. Since many women consume alcohol, detection of a risk-reducing mechanism would have major public health implications. DESIGN: We therefore evaluated the possible interaction between alcohol and folate in a paired nested case-control study among postmenopausal women. SETTING: A total of 24 697 postmenopausal women were included in the 'Diet, Cancer and Health' follow-up study between December 1993 and May 1997. The cohort was followed until December 2000. The study included 388 cases of breast cancer and 388 randomly selected controls were used to estimate the breast cancer incidence rate ratio (IRR) in conditional logistic regression analysis. RESULTS: A previously established association between alcohol intake and risk of breast cancer was present mainly among women with low folate intake. An IRR of 1.19 (95% CI: 0.99-1.42) per 10 g average daily alcohol intake was found for women with a daily folate intake below 300 mug, while among women with a folate intake higher than 350 mug, we could not show an association between the alcohol intake and the breast cancer incidence rate (e.g. folate intake >400 mug; IRR of 1.01 (95% CI: 0.85-1.20)). CONCLUSION: The findings support the evidence that adequate folate intake may attenuate the risk of breast cancer associated with high alcohol intake. SPONSORSHIP: The Danish Cancer Society.     

Low-carbohydrate diets cause obesity, low-carbohydrate diets reverse obesity: a metabolic mechanism resolving the paradox

High-fat diets produce obesity in part because, per calorie, glucose produces greater post-prandial thermogenesis than lipids, an effect probably mediated by glucose-sensing neurons. A very low-carbohydrate/high-fat/high-protein Atkins-type diet produces obesity but is marginally ketogenic in mice. In contrast, high-sucrose/low-fat diets, and very low-carbohydrate/high-fat/low-protein (anti-epileptic) ketogenic diets reverse diet-induced obesity independent of caloric intake. We propose that a non-ketogenic high-fat diet reduces glucose metabolism and signaling in glucose-sensing neurons, thereby reducing post-prandial thermogenesis, and that a ketogenic high-fat diet does not reduce glucose signaling, thereby preventing and/or reversing obesity.     

Antioxidant supplements and risk of breast cancer recurrence and breast cancer-related mortality among postmenopausal women

Despite widespread use, only a few clinical or epidemiological studies have examined the relationship between antioxidant supplements and risk of breast cancer recurrence or breast cancer-related mortality. We used proportional hazards and logistic regression modeling to estimate rate ratios and odds ratios (ORs) for recurrence and mortality among 385 postmenopausal women diagnosed with breast cancer between 1986 and 1988 enrolled into a case-control study on diet and cancer. Women were recontacted with a single questionnaire to ascertain the use of nutritional supplements during 12-14 yr of follow-up time. In multivariable models, antioxidant supplement users compared with nonusers were less likely to have a breast cancer recurrence or breast cancer-related death (OR = 0.54, 95% CI = 0.27-1.04). Vitamin E supplements showed a modest protective effect when used for more than 3 yr (OR = 0.33, 95% CI = 0.10-1.07). Premorbid dietary intake of vitamins C or E from diet, supplements, or both showed no relationship with risk. Risks of recurrence and disease-related mortality were reduced among women using vitamin C and vitamin E supplements for more than 3 yr. Recall bias among proxy respondents for women who died during follow-up may have contributed to these findings. This study provides limited support for the hypothesis that antioxidant supplements may reduce the risk of breast cancer recurrence or breast cancer-related mortality.     

Pre- and postmenopausal breast cancer

It has been postulated that breast cancer is not a single disease, and that the risk factors occurring in premenopausal women are different from those occurring in postmenopausal women. This case-control study of pre- and postmenopausal breast cancer was designed to investigate a variety of variables including age of menarche, parity, age at first full-term birth, breast feeding patterns, age at menopause, and history of oral contraceptive use. The study compared 60 breast cancer cases and 125 matched controls from the same breast cancer screening population. Cases and controls were matched for race, age, place of birth, marital status, education, and annual family income. More cases than controls used oral contraceptives; the differences were statistically significant. The risk ratio estimates were 2.9 (confidence intervals 1.19-7.15). The mean duration of oral contraceptive use was more than two times longer among premenopausal breast cancer cases than controls and five times longer among postmenopausal cases than the controls. The breast cancer cases had significantly more relatives with a history of other cancers than the control group (risk ratio estimate 2.3, P < 0.03). No association was found between height and breast cancer; however, cases were found to be significantly heavier than controls. No differences were found in reproductive variables between breast cancer patients and their matched controls. In addition, a subdivision of breast cancer cases into pre- and postmenopausal groups did not reveal any clear differences in reproductive variables that would support the hypothesis that different specific risk factors are operating during pre- and postmenopausal periods.     

Fat and protein intake and subsequent breast cancer risk in postmenopausal women

The role of diet in the etiology of breast cancer has been extensively evaluated. Case-control studies generally support an association, while cohort studies have produced inconsistent results. This study, carried out on the ORDET cohort, is the first prospective Italian study to address the relation between diet and breast cancer. Female volunteers were recruited from 1987 to 1992 among residents of Varese Province, Northern Italy, an area covered by a cancer registry. A semiquantitative self-administered food questionnaire was completed by participants. After a mean 5.5 yr of follow-up, 56 cases of invasive breast cancer were identified among the 3,367 postmenopausal members; 214 controls were randomly chosen from the cohort, matched to cases for age, menopausal status at recruitment, recruitment center, and recruitment period. The adjusted odds ratios for the highest tertile of intake vs. the lowest were 3.47 [95% confidence interval (CI) = 1.43-8.44] for total fat, 3.78 (95% CI = 0.95-15.0) for animal protein, and 0.42 (95% CI = 0.18-0.95) for total carbohydrates. These findings indicate a significant positive association between total fat and animal protein and risk of breast cancer and an inverse association with carbohydrates and constitute new evidence for a role of diet in the etiology of breast cancer.     

膳食因素与乳腺癌发病及其预防关系的研究进展

乳腺癌在世界范围内是女性发病率和死亡率最高的恶性肿瘤.近年来随着生活水平的提高,我国从传统的膳食模式转而逐渐趋于西方化,而女性乳腺癌发病率也在迅速增长.由于膳食因素一直被研究者视为乳腺癌发病的一个重要影响因素,该文通过查阅既往文献回顾了肉类、牛奶、大豆类食物和蔬菜水果等膳食因素与乳腺癌发病风险的关系.由于膳食因素作为可调控的危险因素,对于乳腺癌的预防具有重要意义,因此亟需设计良好、大样本的研究来明确如何从膳食因素方面降低乳腺癌的发病风险.     

Interaction of nitrate and folate on the risk of breast cancer among postmenopausal women

Ingested nitrate can be endogenously reduced to nitrite, which may form N-nitroso compounds, known potent carcinogens. However, some studies have reported no or inverse associations between dietary nitrate intake and cancer risk. These associations may be confounded by a protective effect of folate, which plays a vital role in DNA repair. We evaluated the interaction of dietary and water nitrate intake with total folate intake on breast cancer risk in the Iowa Women's Health Study. Dietary intake was assessed at study baseline. Nitrate intake from public water was assessed using a historical database on Iowa municipal water supplies. After baseline exclusions, 34,388 postmenopausal women and 2,875 incident breast cancers were included. Overall, neither dietary nor water nitrate was associated with breast cancer risk. Among those with folate intake ≥400 μg/day, breast cancer risk was significantly increased in public water users with the highest nitrate quintile (HR = 1.40, 95% CI = 1.05-1.87) and private well users (HR = 1.38, 95% CI = 1.05-1.82) compared to public water users with the lowest nitrate quintile; in contrast, there was no association among those with lower folate intake. Our findings do not support a previous report of increased risk of breast cancer among individuals with high dietary nitrate but low folate intake.