Vitamins C and E, retinol, beta-carotene and dietary fibre in relation to breast cancer risk: a prospective cohort study.

Association between breast cancer risk and the intake of vitamins C and E, retinol, beta (beta)-carotene, dietary fibre, vegetables, fruit and potatoes was examined in The Netherlands Cohort Study, for 62,573 women aged 55-69 years. After 4.3 years of follow-up, 650 incident breast cancer cases were identified. After adjusting for traditional risk factors, breast cancer risk was not influenced by the intake of beta-carotene, vitamin E, dietary fibre, supplements with vitamin C, vegetables or potatoes. Fruit consumption showed a non-significant inverse association with breast cancer risk (RR highest/lowest quintile = 0.76, 95% CI 0.54-1.08). A small reduction in risk was also observed with increasing intake of dietary vitamin C (RR highest/lowest quintile = 0.77, 95% CI 0.55-1.08). For retinol, a weak positive association was observed (RR highest/lowest quintile = 1.24, 95% CI 0.83-1.83). Among subjects with a high intake of polyunsaturated fatty acids (PUFAs), both beta-carotene and vitamin C intake showed a non-significant inverse association with breast cancer risk (P-trend = 0.15 and 0.16 respectively). Our findings do not suggest a strong role, if any, for intake of vitamins C and E, beta-carotene, retinol, dietary fibre, vegetables, fruit and potatoes in the aetiology of breast cancer.     

Intake of foods and nutrients and cancer of the exocrine pancreas: a population-based case-control study in The Netherlands.

During 1984-88 a population-based case-control study was carried out in the Netherlands in collaboration with the International Agency for Research on Cancer in order to investigate the role of diet in exocrine pancreatic carcinoma. A semi-quantitative food-frequency questionnaire was used to comprehensively assess usual diet about 1 year prior to diagnosis of 164 cases or interview of 480 controls. More than half of the cases were directly interviewed. After controlling for age, gender, response status, life-time cigarette consumption and dietary intake of total energy, monotonic, significantly inverse dose-response effects with estimates of daily consumption of vegetables were found. The significant inverse effect of total cooked vegetables was primarily concentrated in cruciferous vegetables. Consumption of fresh vegetables was also significantly and inversely related to risk. A monotonic, positive dose-response gradient was seen for the consumption of eggs, while consumption of fish was significantly related to risk as well. Among direct respondents, significantly inverse relationships were found for the consumption of legumes, tomatoes, cheese and fermented milk products. Inverse associations with consumption of (subgroups of) fruits were observed in women only. The monotonic, significantly inverse relationship for consumption of low-fibre vegetables and the somewhat weaker, inverse association for high-fibre vegetables in directly interviewed subjects only, may point to protective agents other than vegetable fibre. Although intake of dietary fibre and beta-carotene were both inversely related to risk, simultaneous estimation suggested that beta-carotene or other as yet unknown correlated constituents, rather than dietary fibre, might explain the inverse relationships. A significant protective effect of vitamin C was demonstrated in women but not in men. Our study suggests that, independent of smoking and dietary intake of total energy, low consumption of specific vegetables and possibly fermented milk products and high consumption of eggs and fish may have influenced the development of exocrine pancreatic cancer.     

Vegetable consumption and lung cancer risk: a population-based case-control study in Hawaii

We conducted a population-based study of diet and lung cancer among the multiethnic population of Hawaii in 1983-1985. We completed interviews for 230 men and 102 women with lung cancer and 597 men and 268 women controls, frequency-matched to the patients by age and sex. A quantitative dietary history assessed the usual intake of foods rich in vitamins A and C and carotenoids. A clear dose-dependent negative association was demonstrated between dietary beta-carotene and lung cancer risk in both sexes. After adjusting for smoking and other covariates, the men in the lowest quartile of beta-carotene intake had an odds ratio of 1.9 (95% confidence interval, 1.1-3.2) compared to those in the highest quartile of intake. The corresponding odds ratio for women was 2.7 (95% confidence interval, 1.2-6.1). No clear association was found for retinol, vitamin C, folic acid, iron, dietary fiber, or fruits. All vegetables, dark green vegetables, cruciferous vegetables, and tomatoes showed stronger inverse associations with risk than beta-carotene. This observation suggests that other constituents of vegetables, such as lutein, lycopene, and indoles, and others, may also protect against lung cancer in humans.     

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

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

Diet and vitamin or mineral supplementation and risk of colon cancer by subsite in Canada.

The study assesses the association of diet and vitamin or mineral supplementation with risk of proximal or distal colon cancer. Mailed questionnaires were completed by 1723 newly diagnosed, histologically confirmed colon cancer cases and 3097 population controls between 1994 and 1997 in seven Canadian provinces. Measurement included information on socio-economic status, physical activity, smoking habits, alcohol use, diet and vitamin or mineral supplementation. Odds ratios and 95% confidence intervals were derived through unconditional logistic regression. Linear regression was used to examine that dietary factors affect body mass index. The strongest positive associations between colon cancer risk and increasing total fat intake were observed for proximal colon cancer in men and for distal colon cancer in both men and women. Increased consumption of vegetables, fruit and whole-grain products did not reduce the risk of colon cancer. A modest reduction in distal colon cancer risk was noted in women who consumed yellow-orange vegetables. Significant positive associations were observed between proximal colon cancer risk in men and consumption of red meat and dairy products, and between distal colon cancer risk in women and total intake of meat and processed meat. We also saw strong associations between bacon intake and both subsites of colon cancer in women. When men were compared with women directly by subsite however, the results did not show a corresponding association. A significantly reduced risk of distal colon cancer was noted in women only with increasing intake of dairy products and of milk. Among men and women taking vitamin and mineral supplements for more than 5 years, significant inverse associations with colon cancer were most pronounced among women with distal colon cancer. These findings suggest that dietary risk factors for proximal colon cancer may differ from those for distal colon cancer.     

Vitamins A, C and E and the risk of breast cancer: results from a case-control study in Greece.

Although several dietary compounds are hypothesized to have anticarcinogenic properties, the role of specific micronutrients in the development of breast cancer remains unclear. To address this issue, we assessed intake of retinol, beta-carotene, vitamin C and vitamin E in relation to breast cancer risk in a case-control study in Greece. Eight hundred and twenty women with histologically confirmed breast cancer were compared with 1548 control women. Dietary data were collected through a 115-item semiquantitative food frequency questionnaire. Data were modelled by logistic regression, with adjustment for total energy intake and established breast cancer risk factors, as well as mutual adjustment among the micronutrients. Among post-menopausal women, there was no association between any of the micronutrients evaluated and risk of breast cancer. Among premenopausal women, beta-carotene, vitamin C and vitamin E were each inversely associated with breast cancer risk, but after mutual adjustment among the three nutrients only beta-carotene remained significant; the odds ratio (OR) for a one-quintile increase in beta-carotene intake was 0.84 (95% confidence interval 0.73-0.97). The inverse association observed with beta-carotene intake, however, is slightly weaker than the association previously observed with vegetable intake in these data, raising the possibility that the observed beta-carotene effect is accounted for by another component of vegetables.     

Risk of ovarian carcinoma and consumption of vitamins A, C, and E and specific carotenoids: a prospective analysis.

BACKGROUND: Antioxidant vitamins may decrease risk of cancer by limiting oxidative DNA damage leading to cancer initiation. Few prospective studies have assessed relations between antioxidant vitamins and ovarian carcinoma. METHODS: The authors prospectively assessed consumption of vitamins A, C, and E and specific carotenoids, as well as fruit and vegetable intake, in relation to ovarian carcinoma risk among 80,326 participants in the Nurses' Health Study who had no history of cancer other than nonmelanoma skin carcinoma. Women reported on known and suspected ovarian carcinoma risk factors including reproductive factors, smoking, and use of vitamin supplements on biennial mailed questionnaires from 1976 to 1996. Food frequency questionnaires were included in 1980, 1984, 1986, and 1990. The authors confirmed 301 incident cases of invasive epithelial ovarian carcinoma during 16 years of dietary follow-up (1980-1996). Pooled logistic regression was used to control for age, oral contraceptive use, body mass index, smoking history, parity, and tubal ligation. RESULTS: The authors observed no association between ovarian carcinoma risk and antioxidant vitamin consumption from foods, or foods and supplements together. The multivariate relative risks (95% confidence intervals [CIs]) for ovarian carcinoma among women in the highest versus lowest quintile of intake were 1.04 (95% CI, 0.72-1.51) for vitamin A from foods and supplements; 1.01 (95% CI, 0.69-1.47) for vitamin C; 0.88 (95% CI, 0.61-1.27) for vitamin E; and 1.10 (95% CI, 0.76-1.59) for beta-carotene. Among users of vitamin supplements, the authors found no evidence of an association between dose or duration of any specific vitamin and ovarian carcinoma risk, although the authors had limited power to assess these relations. No specific fruits or vegetables were associated significantly with ovarian carcinoma risk. The authors found no association between ovarian carcinoma and consumption of total fruits or vegetables, or specific subgroups including cruciferous vegetables, green leafy vegetables, legumes, or citrus fruits. Women who consumed at least 2.5 total servings of fruits and vegetables as adolescents had a 46% reduction in ovarian carcinoma risk (relative risk, 0.54, 95% CI, 0.29-1.03; P value for trend 0.04). CONCLUSIONS: These data do not support an important relation between consumption of antioxidant vitamins from foods or supplements, or intake of fruits and vegetables, and incidence of ovarian carcinoma in this cohort. However, modest associations cannot be excluded, and the authors' finding of an inverse association for total fruit and vegetable intake during adolescence raises the possibility that the pertinent exposure period may be much earlier than formerly anticipated.     

Intakes of fruits and vegetables,carotenoids and vitamins A,E, C in relation to the risk of bladder cancer in the ATBC cohort study

We examined the relation between dietary fruit and vegetables, carotenoids and vitamin intakes and the risk of bladder cancer among male smokers in a prospective cohort study. Over a median of 11 years, we followed 27 111 male smokers aged 50-69 years who were initially enrolled in the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study. During this period, 344 men developed bladder cancer. All of these men had completed a 276-food item dietary questionnaire at baseline. Cox proportional hazards models were used to estimate the relative risks and 95% confidence intervals and to simultaneously adjust for age, smoking history, energy intake and intervention group. Consumption of fruits and vegetables was not associated with the risk of bladder cancer (relative risk=1.28; 95% confidence intervals CI: 0.89-1.84, for highest vs lowest quintile). Similarly, no associations were observed for groups of fruits or vegetables (berries and cruciferous vegetables), or for specific fruits and vegetables. Dietary intakes of alpha-carotene, beta-carotene, lycopene, lutein/zeaxanthin, beta-cryptoxanthin, vitamins A, E, and C, and folate were not related to the risk of bladder cancer. These findings suggest that fruit and vegetable intakes are not likely to be associated with bladder cancer risk. However, these results may not be generalisable to non-smokers.     

Dietary fruit and vegetables protect against somatic mutation in vivo,but low or high intake of carotenoids does not

Epidemiological studies have demonstrated protective effects of vegetables and fruit on risk of cancer, but underlying mechanisms remain unclear. Intervention studies have in some cases contradicted previous epidemiological evidence, e.g. for beta-carotene supplementation and lung cancer, emphasizing the need for mechanistic data. We assessed in vivo mutagenic effects of several dietary items using the HPRT (hypoxanthine-guanine phosphoribosyl transferase) gene assay with T-lymphocytes from 312 individuals (158 lung cancer cases, 154 population controls), who provided information on diet and smoking habits. HPRT mutant frequency (MF) was significantly decreased in relation to intake of vegetables, citrus fruits and berries, respectively, as well as calculated vitamin C intake from diet. There was a significant U-shaped association with dietary carotenoid intake, with lowest MF near population average carotenoid intakes and higher mutation frequencies both at low and high intakes, and a similar borderline significant association was observed for beta-carotene. Our study is consistent with known diet-cancer associations and provides novel human in vivo mechanistic support for a cancer-protective effect of vegetables and fruit by modulation of somatic mutagenesis. Our results also provide support for the increase in lung cancer risk observed particularly in smokers in studies of beta-carotene supplementation.     

Dietary beta-carotene and cancer of the prostate: a case-control study in Kyoto, Japan

One hundred patients with prostate cancer and two different control series [100 benign prostatic hyperplasia (BPH) patients and 100 general hospital patients] were matched to each other upon hospital admittance, age (+/- 3 years) and date of admission (+/- 3 months), and directly interviewed during admission from 1981 to 1984 in Kyoto, Japan. Major dietary findings derived from a quantitative food frequency technique for estimating usual diet are as follows. (a) The smaller the dietary intake of beta-carotene and vitamin A as well, the higher the risk, with a highly significant linear trend. From the beta-carotene analyses, the relative risk (95% confidence interval) for the lowest intake quartile relative to the highest was 2.10 (0.98-4.47) for the uncorrected intake, 2.35 (1.08-5.12) for the intake per kg, and 2.94 (1.34-6.44) for the intake per kcal in the comparison with BPH patients; 2.88 (1.31-6.32), 2.56 (1.14-5.76), and 3.50 (1.52-8.06), respectively, in the comparison with hospital controls. The corresponding relative risk obtained from the vitamin A analyses was 2.82 (1.30-6.14), 2.64 (1.24-5.60), and 3.29 (1.47-7.35) in due order in the comparison with BPH patients; 2.69 (1.22-5.94), 4.78 (1.98-11.52), and 3.50 (1.52-8.06) in the comparison with hospital controls. (b) beta-Carotene as well as vitamin A contained in green/yellow vegetables were significantly protective, and those in seaweeds and kelp suggestively protective. But those in fruits appeared to enhance the risk. (c) The risk reduction by dietary beta-carotene and vitamin A was significant in the older men (70-79 years), but not in the younger men (50-69 years). (d) Total energy intake and the dietary intake of fat, protein, carbohydrate, water, fiber, ash, such vitamins as retinol, B1, B2, C, and niacin, and such minerals as calcium, potassium, sodium, phosphorus, and iron were not linked with prostate cancer risk. (e) A protective effect of dietary beta-carotene and vitamin A against prostate cancer could be related to the low overall fat intake in Japan.     

Flavonoids, vitamin C and adenocarcinoma of the stomach

OBJECTIVE: To examine the role of six flavonoid classes (flavanones, flavan-3-ols, flavonols, flavones, anthocyanidins and isoflavones) and vitamin C in the aetiology of stomach cancer. METHODS: Case-control study undertaken in Greece in the 1980s. Dietary information was obtained from 110 patients with incident stomach adenocarcinoma and 100 control patients. Flavonoid estimates were based on the recently released database of the US Department of Agriculture. RESULTS: In models including sociodemographic variables, energy intake, vegetables, fruits and, alternatively, vitamin C the six flavonoid classes, only flavanones and vegetables remained significantly inversely associated with stomach cancer risk. The odds ratio (95% confidence intervals) per one standard deviation increase of intake of flavanones was 0.55 (0.31-0.96) whereas for vitamin C it was 1.05 (0.46-2.41). When fruits and vegetables were not adjusted for, both vitamin C and several flavonoid categories were inversely associated with stomach cancer risk, but these associations could be attributed to other compounds in these foods. CONCLUSIONS: Among the major flavonoid classes studied, only flavanone intake is inversely associated with stomach cancer risk and could account for the apparent protective effect of fruit intake against this form of cancer. Additional factors, however, are likely to be involved in the consistent protection conveyed by vegetables.     

Calcium, vitamin D, sunshine exposure, dairy products and colon cancer risk (United States)

Objective: Epidemiologic studies on calcium, vitamin D and colon cancer are inconsistent, whereas experimental studies more regularly show a protective effect. To evaluate potential sources of inconsistencies, data from a large case–control study were analyzed, stratifying on potential effect modifiers. Methods: Data were collected by certified interviewers in Northern California, Utah and Minnesota. Analyses included 1993 incident colon cancer cases and 2410 population-based controls. Multivariate logistic regression models included age, sex, BMI, family history, physical activity, intake of energy, dietary fiber, aspirin and NSAIDs. Results: Dietary calcium was inversely associated with colon cancer risk in men (OR highest vs lowest quintile = 0.6, 95% CI = 0.5–0.9) and women (OR = 0.6, 95% CI = 0.4–0.9). No statistically significant associations were observed for dietary vitamin D or sunshine exposure. Consumption of total low-fat dairy products was associated with a statistically significantly decreased risk in men and women (ORs highest vs lowest category of intake = 0.8 and 0.7 respectively). Calcium supplement use was inversely associated with risk in both sexes (ORs use vs non-use = 0.8). Vitamin D supplements were inversely associated with risk in men (OR = 0.5) and women (OR = 0.6) but confidence limits included 1.0. Conclusions: These data provide additional support of an inverse association between high levels of calcium intake and colon cancer risk.     

Carotenoids, antioxidants and ovarian cancer risk in pre- and postmenopausal women.

An inverse association between ovarian cancer risk, carotenoids and antioxidant vitamins has been suggested by several epidemiologic studies and 1 experimental trial of a vitamin A analogue. From a population-based study of 549 cases of ovarian cancer and 516 controls, we estimated the consumption of the antioxidant vitamins A, C, D and E and various carotenoids, including alpha- and beta-carotene and lycopene, using a validated dietary questionnaire. Multivariate logistic regression was used to calculate the exposure odds ratios adjusted for established ovarian cancer risk factors. Intakes of carotene, especially alpha-carotene, from food and supplements were significantly and inversely associated with risk for ovarian cancer, predominantly in postmenopausal women. Intake of lycopene was significantly and inversely associated with risk for ovarian cancer, predominantly in premenopausal women. Food items most strongly related to decreased risk for ovarian cancer were raw carrots and tomato sauce. Consumption of fruits, vegetables and food items high in carotene and lycopene may reduce the risk of ovarian cancer.     

Dietary intake of fiber and decreased risk of cancers of the colon and rectum: evidence from the combined analysis of 13 case-control studies.

BACKGROUND: Colorectal cancer is a major public health problem in both North America and western Europe, and incidence and mortality rates are rapidly increasing in many previously low-risk countries. It has been hypothesized that increased intakes of fiber, vitamin C, and beta carotene could decrease the risk of colorectal cancer. PURPOSE: The objective of this study was to examine the effects of fiber, vitamin C, and beta-carotene intakes on colorectal cancer risk in a combined analysis of data from 13 case-control studies previously conducted in populations with differing colorectal cancer rates and dietary practices. The study was designed to estimate risks in the pooled data, to test the consistency of the associations across the studies, and to examine interactions of the effects of the nutrients with cancer site, sex, and age. METHODS: Original data records for 5287 case subjects with colorectal cancer and 10,470 control subjects without disease were combined. Logistic regression analysis was used to estimate relative risks and confidence intervals for intakes of fiber, vitamin C, and beta carotene, with the effects of study, sex, and age group being adjusted by stratification. RESULTS: Risk decreased as fiber intake increased; relative risks were 0.79, 0.69, 0.63, and 0.53 for the four highest quintiles of intake compared with the lowest quintile (trend, P < .0001). The inverse association with fiber is seen in 12 of the 13 studies and is similar in magnitude for left- and right-sided colon and rectal cancers, for men and for women, and for different age groups. In contrast, after adjustment for fiber intake, only weak inverse associations are seen for the intakes of vitamin C and beta carotene. CONCLUSION: This analysis provides substantive evidence that intake of fiber-rich foods is inversely related to risk of cancers of both the colon and rectum. IMPLICATIONS: If causality is assumed, we estimate that risk of colorectal cancer in the U.S. population could be reduced about 31% (50,000 cases annually) by an average increase in fiber intake from food sources of about 13 g/d, corresponding to an average increase of about 70%.     

Association of dietary vitamin A, carotenoids, and other antioxidants with the risk of ovarian cancer.

Antioxidants may protect the ovaries from oxidative damage and reduce the risk of ovarian cancer. Although a few studies have examined the relation of antioxidant intake to the risk of ovarian cancer, the results have been inconclusive. Questions still remain regarding the effects of confounding factors, such as menopause, tobacco smoking, and alcohol drinking, on the association between antioxidants and ovarian cancer development. OBJECTIVE: To examine the association of the consumption of micronutrients from foods and supplements with the risk of ovarian cancer. METHODS: A structured questionnaire was administered to 558 histologically confirmed epithelial ovarian cancer cases and 607 population controls from a multiethnic, population-based case-control study conducted between 1993 and 1999 in Hawaii and Los Angeles. RESULTS: Overall, vitamin A and carotene intakes were modestly associated with a reduced risk of ovarian cancer. Inverse gradients in ovarian cancer risk with increasing dietary intake of vitamin A and beta-carotene were somewhat stronger among women with mucinous histologic types, smokers, and nondrinkers. A significant positive trend in risk associated with increasing beta-cryptoxanthin intake was observed among postmenopausal women, among women with nonmucinous tumors, and among nonsmokers. The intake of other carotenoids and antioxidants, either from foods or supplements, was unrelated to ovarian cancer risk. CONCLUSION: Our findings suggest that dietary vitamin A and beta-carotene are modestly protective against ovarian cancer, particularly among smokers. Our data suggest a role for retinoic acid signaling pathways in ovarian carcinogenesis.     

Meta-analysis of studies on breast cancer risk and diet: the role of fruit and vegetable consumption and the intake of associated micronutrients

A meta-analysis was carried out, in order to summarise published data on the relationship between breast cancer, fruit and vegetable consumption and/or the intake of beta-carotene and vitamin C. Relative risks were extracted from 26 published studies from 1982 to 1997. Random and fixed effects models were used. Between studies, heterogeneity was found for vegetables, fruit, vitamin C but not for beta-carotene. Summary relative risk (RR) estimates based upon a random effects model, except for beta-carotene, for 'high consumption' compared with 'low consumption', derived from the studies satisfying the inclusion criteria were as follows: vegetable consumption: RR=0.75 (95% CI (confidence interval) 0.66-0.85) from 17 studies; fruit consumption: RR=0.94 (95% CI 0.79-1.11) from 12 studies; vitamin C: RR=0.80 (95% CI 0.68-0.95) from 9 studies; beta-carotene: RR=0.82 (95% CI 0.76-0.91) from 11 studies. This analysis confirms the association between intake of vegetables and, to a lesser extent, fruits and breast cancer risk from published sources. Increasing vegetable consumption might reduce the risk of breast cancer.     

Folate, vitamin C, and cervical intraepithelial neoplasia.

A case-control study was designed to assess the relationship between cervical intraepithelial neoplasia (CIN) and folate in serum, red blood cells, and diet. The association between CIN and dietary vitamin C was also investigated. Cases were selected from women with biopsy-confirmed CIN. Controls were age-, race-, and clinic-matched women with normal cervical (Pap) smears. Study participants completed self-administered food frequency (n = 100 matched pairs) and health (n = 102 matched pairs) questionnaires. Fasting venous blood samples were collected for serum (n = 98 matched pairs) and red cell (n = 68 matched pairs) folate assays. Conditional logistic regression models were used to estimate crude odds ratios and odds ratios adjusted for smoking, income, number of sexual partners, frequency of cervical smear, use of spermicidal contraceptive agents, history of genital warts, and Quetelet index. Dietary intake variables were adjusted for total energy intake prior to logistic regression. A protective effect of red cell folate was evident with adjusted odds ratios (95% confidence intervals) of 0.1 (0.0-0.4), 0.6 (0.2-2.0), and 0.5 (0.2-1.9) for those in quartiles 4 (highest), 3, and 2 compared to quartile 1 (lowest). Supporting evidence for the protective effect of folate was provided by inverse associations between CIN and folate in both serum and diet. An inverse association was also found between CIN and dietary vitamin C with adjusted odds ratios (95% confidence intervals) of 0.2 (0.0-0.7), 0.6 (0.2-1.6), and 0.6 (0.2-1.8) for those in quartiles 4, 3, and 2, respectively, compared to quartile 1. These findings support dietary recommendations, such as those of the American Cancer Society, the National Cancer Institute, and the U.S. Dietary Guidelines, which allow for adequate intake of folate and vitamin C, both of which are found in good quantity in fruits and vegetables. Increased consumption of legumes and whole grains is also in accord with current dietary recommendations, and both of these types of foods are good sources of folates.     

Intakes of fruits, vegetables, vitamins A, C, and E, and carotenoids and risk of renal cell cancer.

BACKGROUND: Fruits and vegetables rich in antioxidants have been proposed to reduce the risk of renal cell cancer. However, few prospective studies have examined the intakes of fruits, vegetables, and antioxidant vitamins in relation to the risk of renal cell cancer. METHODS: We prospectively examined the associations between the intakes of fruits, vegetables, vitamins A, C, and E, and carotenoids and risk of renal cell cancer in women and men. We followed 88,759 women in the Nurses' Health Study from 1980 to 2000, and 47,828 men in the Health Professionals Follow-up Study from 1986 to 2000. We assessed dietary intake every 2 to 4 years using a validated semiquantitative food frequency questionnaire. The Cox proportional hazards model was used to estimate study-specific multivariate relative risks (RR), which were pooled using a random effects model. RESULTS: A total of 248 (132 women and 116 men) incident renal cell cancer cases were ascertained during 2,316,525 person-years of follow-up. The consumption of fruits and vegetables was associated with a decreased risk of renal cell cancer in men (multivariate RR, 0.45; 95% CI, 0.25-0.81, for >or=6 servings of fruit and vegetable intake/d versus <3 servings/d; P test for trend = 0.02), but not in women (multivariate RR, 1.17; 95% CI, 0.66-2.07, for the same contrast; P test for trend = 0.25; P test for between-studies heterogeneity = 0.02). Intakes of vitamins A and C from food and carotenoids were inversely associated with the risk of renal cell cancer in men only, but we cannot exclude the possibility that this was due to other factors in fruit and vegetables. No clear association was observed for vitamin E in women or men. CONCLUSIONS: Fruit and vegetable consumption may reduce the risk of renal cell cancer in men.     

Vitamin A, beta-carotene, and the risk of cancer: a prospective study

A cohort of 10,473 residents of Leisure World, Laguna Hills, CA, who were initially free of cancer were followed from 1981 to 1986. A health survey questionnaire completed by all cohort members included usual frequencies of consumption of certain food items, including vegetables, fruits, dairy products, liver, and cereal, as well as specific information on brand and formulation of vitamin supplements containing vitamins A, C, or E. Pathologic diagnosis of incident cancer was confirmed in 643 persons (56 lung, 110 colon, 59 bladder, 93 prostate, 123 female breast, and 202 cancers of other sites). Our study found little indication that increased intake of vitamin A or beta-carotene from the diet or supplements protects against the development of cancer overall. Dietary vitamin A intake was highly associated with smoking status; 25% of current smokers were in the highest third of dietary vitamin A consumption versus 32% of past smokers and 36% of never-smokers. In males who never smoked there was some indication that cancer rates decreased with increasing vitamin A intake, but the results were not statistically significant.     

Diet and vitamin or mineral supplementation and risk of rectal cancer in Canada

The study examines the relation of diet and vitamin or mineral supplementation with risk of rectal cancer. Mailed questionnaires were completed by 1 380 newly diagnosed patients with histologically confirmed rectal cancer and 3 097 population controls between 1994 and 1997 in seven Canadian provinces. Measurement included information on socio-economic status, lifestyle, diet and vitamin or mineral supplementation. We derived odds ratios and 95% confidence intervals through unconditional logistic regression. Total of consumption of vegetables, fruit and whole-grain products did not reduce the risk of rectal cancer. Consumption of cruciferous vegetables was inversely associated with risk of rectal cancer among women only, as did chicken intake among men. The strongest dietary association with increased rectal cancer risk appeared in males with increasing total fat intake and in females with bacon intake. Vitamin and mineral supplementation showed significant inverse associations with rectal cancer in women only. These findings suggest that dietary risk factors for rectal cancer in women may differ from those in men.