Dietary carotenoids and risk of breast cancer

BACKGROUND: Many studies of fruit and vegetable consumption showed inverse associations with breast cancer risk, suggesting the potential importance of carotenoids (and other phytochemicals) contained in these foods. To date, however, only one prospective cohort study has examined dietary carotenoids other than beta-carotene in relation to breast cancer risk. OBJECTIVE: Our aim was to examine the relations between dietary intakes of beta-carotene, alpha-carotene, beta-cryptoxanthin, lycopene, and lutein + zeaxanthin and breast cancer risk in a large cohort study of Canadian women. DESIGN: A case-cohort analysis was undertaken in a cohort of 56 837 women who were enrolled in the Canadian National Breast Screening Study and who completed a self-administered dietary questionnaire. During follow-up to the end of 1993 a total of 1589 women were diagnosed with biopsy-confirmed incident breast cancer. For comparison, a subcohort of 5681 women was randomly selected. After exclusions for various reasons, the analyses were based on 1452 cases and 5239 noncases. RESULTS: We found no clear association between intakes of any of the studied carotenoids and breast cancer risk in the study population as a whole or in subgroups defined by smoking status; relative body weight (assessed by body mass index); intakes of total fat, energy, alcohol, or folic acid; family history of breast cancer; or menopausal status. CONCLUSIONS: Our data do not support any association between dietary intakes of the studied carotenoids and breast cancer risk. However, prospective cohort studies of carotenoids in relation to breast cancer are scarce and further studies are warranted.     

Dietary calcium intake and breast cancer risk among Chinese women in Shanghai

Limited epidemiological evidence suggests that calcium intake may be related to breast cancer risk. Data from a large, population-based, case-control study (n = 1,459 cases, 1,556 controls) conducted in Shanghai, China, between 1996 and 1998 were used to investigate the association between calcium intake and risk for breast cancer. Diet was assessed using a quantitative food-frequency questionnaire. The multivariate-adjusted odds ratio (OR) comparing all women combined in the highest to lowest deciles of total calcium intake was 0.74 (95% confidence interval [CI] = 0.46-1.20). Whereas calcium primarily derived from poultry was inversely associated with risk for breast cancer (comparing the highest to lowest quintile OR = 0.71, 95% CI = 0.55-0.93) with a statistically significant test for trend, calcium derived from milk, seafood, fruit, and vegetables was not associated with risk of breast cancer. Given that breast cancer is one of the top contributors to cancer incidence worldwide, even a moderate inverse association between calcium and breast cancer risk, if confirmed, could have important public health implications in breast cancer prevention.     

Dietary patterns and breast cancer risk in Korean women

We evaluated the association between dietary patterns and breast cancer risk according to menopausal and hormone receptor status among Korean women. In a study with 357 cases and 357 age-matched controls, dietary patterns (vegetable-seafood and meat-starch) were derived via principle component analysis based on 39 food groups from a food frequency questionnaire. The relation between dietary patterns and breast cancer risk was assessed by using multivariate logistic regression. The vegetable-seafood pattern was inversely associated with breast cancer risk [odds ratio (OR) and 95% confidence interval (CI) for high vs. low intake = 0.14 (0.08-0.25); P for trend < 0.001]. No association between the meat-starch pattern and breast cancer risk was found. The association between dietary patterns and breast cancer risk was not modified by menopausal and combined hormone receptor status. These findings indicate that a diet rich in vegetables and seafood is associated with a decreased breast cancer risk in Korean women.     

Dietary B vitamin and methionine intakes and breast cancer risk among Chinese women

Methionine, folate, vitamin B(6), vitamin B(12), niacin, and riboflavin intakes may be related to breast carcinogenesis. These associations may vary by breast cancer type. Using the prospective cohort Shanghai Women's Health Study (1997-2008) including 718 Chinese breast cancer cases, the authors evaluated baseline dietary intake of these factors and breast cancer risk and whether the associations varied by menopausal status and estrogen receptor (ER) and progesterone receptor (PR) status. They estimated associations using hazard ratios and 95% confidence intervals from Cox proportional hazards regression models and stratified analyses by menopausal status and ER/PR status. Lowest quantile of intake was used as the comparison group. For postmenopausal women, dietary intakes of methionine and B vitamins were not associated with breast cancer risk. For premenopausal women, higher intake of folate was associated with decreased breast cancer risk (hazard ratio = 0.58, 95% confidence interval: 0.34, 0.99 for the highest vs. lowest quintile of intake). Only niacin intake was associated with ER+/PR+ breast cancer risk (hazard ratio = 1.62, 95% confidence interval: 1.07, 2.46; P for trend = 0.04 for the highest vs. lowest quartile of intake). Findings support the hypothesis that high folate intake may reduce breast cancer risk and that the association may vary by menopausal and ER/PR status.     

Dietary carotenoids and risk of coronary artery disease in women

BACKGROUND: Numerous studies have shown that higher intakes or higher blood concentrations of carotenes are associated with a lower risk of coronary artery disease (CAD). Given the null results in trials of beta-carotene supplementation, considerable attention has focused on the potential role of other dietary carotenoids in the prevention of CAD. OBJECTIVE: Our objective was to prospectively examine the relation between dietary intakes of specific carotenoids and risk of CAD in women. DESIGN: In 1984, 73 286 female nurses completed a semiquantitative food-frequency questionnaire that assessed their consumption of carotenoids and various other nutrients. The women were followed for 12 y for the development of incident CAD (nonfatal myocardial infarction and fatal CAD), and dietary information was updated in 1986, 1990, and 1994. RESULTS: During 12 y of follow-up (803 590 person-years), we identified 998 incident cases of CAD. After adjustment for age, smoking, and other CAD risk factors, we observed modest but significant inverse associations between the highest quintiles of intake of beta-carotene and alpha-carotene and risk of CAD but no significant relation with intakes of lutein/zeaxanthin, lycopene, or beta-cryptoxanthin. For women in the highest compared with the respective lowest quintile of intake, the relative risks for beta-carotene and alpha-carotene were 0.74 (95% CI: 0.59, 0.93) and 0.80 (95% CI: 0.65, 0.99), respectively. The association between the specific carotenoids and CAD risk did not vary significantly by current smoking status. CONCLUSION: Higher intakes of foods rich in alpha-carotene or beta-carotene are associated with a reduction in risk of CAD.     

Dietary carotenoids and genetic instability modify bladder cancer risk

In vitro and in vivo studies have shown that carotenoid supplementation is associated with decreased DNA damage, but the role of dietary carotenoids in cancer risk remains controversial because epidemiologic studies have yielded conflicting results. Limited data exist regarding the role of dietary carotenoids in the context of constitutional genetic instability in cancer risk. This case-control study estimated dietary carotenoid intake [microg/(kJ . d)] from a FFQ for 423 patients with bladder cancer and 467 healthy controls, and quantified baseline and benzo[a]pyrene diol epoxide (BPDE)- and gamma-radiation-induced DNA damage in the peripheral blood lymphocytes using the comet assay. Overall, intake of total carotenoids was lower (P < 0.01) for bladder cancer cases (mean +/- SD: 1273.4 +/- 688.9) compared with healthy controls (1501.3 +/- 791.5). When categorized into quartiles, there was an inverse association between increasing levels of carotenoid intake and bladder cancer risk with greatest protective effect [odds ratio (OR) = 0.56, 95% CI, 0.37-0.85] in the quartile with the highest level of intake. Baseline and mutagen-induced DNA damage was significantly higher in cases than in controls; when analyzed jointly with carotenoid intake, high DNA damage and low carotenoid intake were associated with the highest risk. For example, with high baseline DNA damage and low total carotenoid intake, the OR was 3.08 (95% CI, 1.64-5.77); with high baseline DNA damage and high total carotenoid intake, the risk was somewhat attenuated (OR = 2.49, 95% CI, 1.28-4.84). The risk was decreased further for low baseline DNA damage and low total carotenoid intake (OR = 2.18; 95% CI, 1.13-4.22). This study provides evidence of a preventive role for carotenoids in bladder cancer, and these data may have important implications for cancer prevention, especially for individuals susceptible to DNA damage.     

Dietary phytoestrogens and breast cancer risk

BACKGROUND: A high intake of phytoestrogens, particularly isoflavones, has been suggested to decrease breast cancer risk. Results from human studies are inconclusive. OBJECTIVE: We investigated the association between phytoestrogen intake and breast cancer risk in a large prospective study in a Dutch population with a habitually low phytoestrogen intake. DESIGN: The study population consisted of 15 555 women aged 49-70 y who constituted a Dutch cohort of the European Prospective Investigation into Cancer and Nutriton (EPIC; 1993-1997). Data concerning habitual dietary intake in the preceding year were obtained by using a validated food-frequency questionnaire. The content of isoflavones and lignans in relevant food items was estimated through a literature search, the use of food-composition tables, and contact with experts. Newly diagnosed breast cancer cases up to 1 January 2001 were identified through linkage with the Comprehensive Cancer Center Middle Netherlands. Hazard ratios for the disease were estimated by Cox proportional hazard analysis for quartiles of isoflavone and lignan intake. Associations were adjusted for known breast cancer risk factors and daily energy intake. RESULTS: A total of 280 women were newly diagnosed with breast cancer during follow-up. The median daily intakes of isoflavones and lignans were 0.4 (interquartile range: 0.3-0.5) and 0.7 (0.5-0.8) mg/d, respectively. Relative to the respective lowest intake quartiles, the hazard ratios for the highest intake quartiles for isoflavones and lignans were 1.0 (95% CI: 0.7, 1.5) and 0.7 (0.5, 1.1), respectively. Tests for trend were nonsignificant. CONCLUSION: In Western populations, a high intake of isoflavones or mammalian lignans is not significantly related to breast cancer risk.     

Dietary flavonoid intake and breast cancer risk among women on Long Island

Flavonoids are found in a variety of foods and have anticarcinogenic properties in experimental models. Few epidemiologic studies have examined whether flavonoid intake is associated with breast cancer in humans. In this study, the authors investigated whether dietary flavonoid intake was associated with reduced risk of breast cancer in a population-based sample of US women. They conducted a case-control study among women who resided in Nassau and Suffolk counties on Long Island, New York. Cases and controls were interviewed about known and suspected risk factors and asked to complete a food frequency questionnaire regarding their average intake in the prior 12 months. A total of 1,434 breast cancer cases and 1,440 controls provided adequate responses. A decrease in breast cancer risk was associated with flavonoid intake; the decrease was most pronounced among postmenopausal women for flavonols (odds ratio (OR) = 0.54, 95% confidence interval (CI): 0.40, 0.73), flavones (OR = 0.61, 95% CI: 0.45, 0.83), flavan-3-ols (OR = 0.74, 95% CI: 0.55, 0.99), and lignans (OR = 0.69, 95% CI: 0.51, 0.94). The authors conclude that intake of flavonols, flavones, flavan-3-ols, and lignans is associated with reduced risk of incident postmenopausal breast cancer among Long Island women. These results suggest that US women can consume sufficient levels of flavonoids to benefit from their potential chemopreventive effects.     

Dietary fat and risk of breast cancer

The relationship between dietary fat and subsequent risk of breast cancer was studied in 3988 initially cancer-free Finnish women aged 20-69 y. During a follow-up period of 20 y, 54 breast-cancer cases were diagnosed. Risk of breast cancer was significantly inversely related to energy intake and nonsignificantly inversely related to absolute fat intake. A positive association between energy-adjusted total fat intake and occurrence of breast cancer was also observed. The relative risk in the highest tertile as compared with the lowest tertile was 1.7 (95% confidence limits 0.6-4.8). The corresponding relative risks were 1.4 (0.5-3.7) for saturated fatty acids, 2.7 (1.0-7.4) for monounsaturated fatty acids, 1.2 (0.6-2.8) for polyunsaturated fatty acids, and 2.2 (1.0-5.0) for cholesterol intake. Adjustment for different potential confounding factors did not alter the results. The present data suggest that breast cancer is associated inversely with energy intake and weakly positively with energy-adjusted fat intake.     

Occupations and breast cancer risk among Chinese women in urban Shanghai

BACKGROUND: Although, an elevated risk of breast cancer has been suggested for a number of occupations, many earlier studies were limited by selection biases, the incomplete assessment of job histories, and the inability to control for confounding. METHODS: We examined the relationship between occupational history and breast cancer risk using data from a population-based case-control study of 1,458 cases and 1,556 age-matched controls (90% response rate) conducted in Shanghai, China. Unconditional logistic regression models were used to derive odds ratios (ORs) and 95% confidence intervals (95% CIs) of breast cancer risk associated with occupations and duration of employment adjusting for non-occupational risk factors. RESULTS: The following occupations were found to be associated with an increased risk of breast cancer: laboratory technicians (OR 9.94, 95% CI 1.20-82.37), telephone and telegraph operators (OR 4.63, 95% CI 1.85-11.59), leather and fur processors (OR 3.25, 95% CI 1.11-9.53), and glass-manufacturing workers (OR 2.08, 95% CI 1.14-3.82). A dose-response pattern for years of employment was observed for leather and fur processors (P = 0.02) and glass-manufacturing workers (P = 0.01). Stratified analyses also revealed dose-response relationships between the risk of breast cancer and years of employment as inspector and product analysts among pre-menopausal women (P = 0.02), and as farmers among post-menopausal women (P = 0.04). CONCLUSIONS: This study found that several occupations are associated with an increased risk of breast cancer among women. Studies examining various occupational exposures in these high-risk occupations are warranted to identify carcinogens that may play a role in the increased breast cancer risk.     

Dietary factors and the risk of breast cancer

We evaluated the risk of breast cancer in relation to the frequency of consumption of a few selected dietary items. Data were used from a case‐control study of 1,108 histologically confirmed breast cancer patients and 1,281 control subjects who were in the hospital for acute conditions unrelated to any of the established or suspected risk factors for breast cancer. Moderately elevated risk estimates were associated with higher levels of fat consumption in seasonings [butter, margarine, and oil, relative risk (RR) = 1.34, 95% confidence interval (CI) = 1.06–1.71] and meat (RR = 1.36, 95% CI = 1.12–1.65), whereas a reduced risk (RR = 0.42, 95% CI = 0.34–0.51) was associated with a more frequent green vegetable consumption. It was not possible to show that these associations were incidental, because allowance for several identified potential confounding factors, including the major identified or potential risk factors for breast cancer, did not materially modify the risk estimates. Further, no appreciable interaction emerged with age or menopausal status, because the diet‐related risk estimates were similar in pre‐ or postmenopausal women. However, the implications of these findings in terms of specific micronutrients (e.g., retinal or β‐carotene) and biological correlates are still unclear. Alcohol consumption was significantly greater among breast cancer cases, with a multivariate risk estimate of 2.92 for the highest level. Thus, the present findings confirm that various aspects of diet may influence the risk of breast cancer, although the small amount of available knowledge does introduce serious uncertainties in any discussion of the potential implications in terms of prevention on a public health scale.     

Dietary fat and the risk of breast cancer

Age-adjusted dietary fat intake of 133 incident Dutch breast cancer cases was significantly (p less than 0.01) higher than in 289 apparently healthy controls (mean and standard deviation: 102 +/- 36 g and 92 +/- 30 g, respectively). The age-adjusted relative odds of breast cancer showed a positive trend (p less than 0.05) with increasing fat intake. The multivariate adjusted relative odds was 3.5 (95% Cl = 1.6-7.6) for subjects in the highest quintile of fat intake (above 113 g) compared to those in the lowest quintile (below 65 g); this corresponds to a 30% increased risk per 10% of energy derived from fat. The association could not be attributed to energy intake, nor to the degree of saturation of the fat nor to any specific dietary source of fat.     

Dietary factors and the risk of breast cancer

We evaluated the risk of breast cancer in relation to the frequency of consumption of a few selected dietary items. Data were used from a case-control study of 1,108 histologically confirmed breast cancer patients and 1,281 control subjects who were in the hospital for acute conditions unrelated to any of the established or suspected risk factors for breast cancer. Moderately elevated risk estimates were associated with higher levels of fat consumption in seasonings [butter, margarine, and oil, relative risk (RR) = 1.34, 95% confidence interval (CI) = 1.06-1.71] and meat (RR = 1.36, 95% CI = 1.12-1.65), whereas a reduced risk (RR = 0.42, 95% CI = 0.34-0.51) was associated with a more frequent green vegetable consumption. It was not possible to show that these associations were incidental, because allowance for several identified potential confounding factors, including the major identified or potential risk factors for breast cancer, did not materially modify the risk estimates. Further, no appreciable interaction emerged with age or menopausal status, because the diet-related risk estimates were similar in pre- or postmenopausal women. However, the implications of these findings in terms of specific micronutrients (e.g., retinol or beta-carotene) and biological correlates are still unclear. Alcohol consumption was significantly greater among breast cancer cases, with a multivariate risk estimate of 2.92 for the highest level. Thus, the present findings confirm that various aspects of diet may influence the risk of breast cancer, although the small amount of available knowledge does introduce serious uncertainties in any discussion of the potential implications in terms of prevention on a public health scale.     

Dietary intake of vitamin B(6) and risk of breast cancer in Taiwanese women

Background

B vitamins, including vitamin B₆, are coenzymes that are important for DNA integrity and stability. Deficiencies in B vitamins may promote tumor carcinogenesis.

Methods

We examined the association of dietary vitamin B₆ intake with overall breast cancer risk and breast cancers stratified by hormone receptor status. This case-control study included 391 breast cancer cases and 782 control subjects enrolled at the Tri-Service General Hospital in Taipei, Taiwan. Energy-adjusted intake of vitamin B₆ was derived from a food frequency questionnaire. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression.

Results

As compared with women in the lowest tertile, the multivariate-adjusted ORs for breast cancer among women in the second and highest tertiles of vitamin B₆ intake were 0.78 (95% CI, 0.64–2.52) and 0.64 (0.26–0.92), respectively. In addition, higher vitamin B₆ intake was associated with a significantly lower risk of developing ER-negative breast tumors.

Conclusions

Our findings suggest that higher intake of vitamin B₆ is associated with a reduction in breast cancer risk, particularly ER-negative tumors.Key words: breast cancer, ER-defined breast tumors, 1-carbon metabolism, vitamin B₆     

Plasma carotenoids, retinol, and tocopherols and risk of breast cancer

The roles of carotenoids, retinol, and tocopherols in breast cancer etiology have been inconclusive. The authors prospectively assessed the relations between plasma alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, lutein/zeaxanthin, retinol, alpha-tocopherol, and gamma-tocopherol and breast cancer risk by conducting a nested case-control study using plasma collected from women enrolled in the Nurses' Health Study. A total of 969 cases of breast cancer diagnosed after blood draw and prior to June 1, 1998, were individually matched to controls. The multivariate risk of breast cancer was 25-35% less for women with the highest quintile compared with that for women with the lowest quintile of alpha-carotene (odds ratio (OR) = 0.64, 95% confidence interval (CI): 0.47, 0.88; p(trend) = 0.01), beta-carotene (OR = 0.73, 95% CI: 0.53, 1.02; p(trend) = 0.01), lutein/zeaxanthin (OR = 0.74, 95% CI: 0.55, 1.01; p(trend) = 0.04), and total carotenoids (OR = 0.76, 95% CI: 0.55, 1.05; p(trend) = 0.05). The inverse association observed with alpha-carotene and breast cancer was greater for invasive cancers with nodal metastasis. The authors conclude that some carotenoids are inversely associated with breast cancer. Although the association was strongest for alpha-carotene, the high degree of collinearity among plasma carotenoids limits our ability to conclude that this association is specific to any individual carotenoid.     

Dietary carotenoids and risk of colorectal cancer in a pooled analysis of 11 cohort studies

Dietary carotenoids have been hypothesized to protect against epithelial cancers. The authors analyzed the associations between intakes of specific carotenoids (alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein + zeaxanthin, and lycopene) and risk of colorectal cancer using the primary data from 11 cohort studies carried out in North America and Europe. Carotenoid intakes were estimated from food frequency questionnaires administered at baseline in each study. During 6-20 years of follow-up between 1980 and 2003, 7,885 incident cases of colorectal cancer were diagnosed among 702,647 participants. The authors calculated study-specific multivariate relative risks and then combined them using a random-effects model. In general, intakes of specific carotenoids were not associated with colorectal cancer risk. The pooled multivariate relative risks of colorectal cancer comparing the highest quintile of intake with the lowest ranged from 0.92 for lutein + zeaxanthin to 1.04 for lycopene; only for lutein + zeaxanthin intake was the result borderline statistically significant (95% confidence interval: 0.84, 1.00). The associations observed were generally similar across studies, for both sexes, and for colon cancer and rectal cancer. These pooled data did not suggest that carotenoids play an important role in the etiology of colorectal cancer.     

Dietary carbohydrates, fiber, and breast cancer risk

Dietary fiber, fiber fractions, carbohydrate, glycemic index, and glycemic load were prospectively assessed five times over 18 years with a validated food frequency questionnaire in relation to breast cancer risk among 88,678 women (aged 34-59 years at baseline) in the Nurses' Health Study. Incident breast cancer occurred in 4,092 of these women between 1980 and 1998. The authors observed no material association between carbohydrate intake, glycemic index and glycemic load, total dietary fiber intake, and breast cancer risk. The relative risks for the highest versus the lowest quintile of intake were 0.97 (95% confidence interval (CI): 0.87, 1.08) for carbohydrates, 1.08 (95% CI: 0.97, 1.19) for glycemic index, 0.99 (95% CI: 0.89, 1.10) for glycemic load, and 0.98 (95% CI: 0.87, 1.11) for fiber. The relative risk comparing those in the highest 0.7% of fiber intake (>30 g/day) with those in the lowest 10% of fiber intake (< or =10 g/day) was 0.68 (95% CI: 0.43, 1.06). Analyses stratified by menopausal status and body mass index also showed no clear risk pattern. In this cohort of middle-aged women, no overall association was found for dietary carbohydrates, glycemic index and glycemic load, and breast cancer risk. This study also confirmed the lack of an overall association between intake of fiber and fiber types and breast cancer risk observed in other prospective studies.