Analysis of patterns of food intake in nutritional epidemiology: food classification in principal components analysis and the subsequent impact on estimates for endometrial cancer.

OBJECTIVE: To assess the effect of different methods of classifying food use on principal components analysis (PCA)-derived dietary patterns, and the subsequent impact on estimation of cancer risk associated with the different patterns. METHODS: Dietary data were obtained from 232 endometrial cancer cases and 639 controls (Western New York Diet Study) using a 190-item semi-quantitative food-frequency questionnaire. Dietary patterns were generated using PCA and three methods of classifying food use: 168 single foods and beverages; 56 detailed food groups, foods and beverages; and 36 less-detailed groups and single food items. RESULTS: Classification method affected neither the number nor character of the patterns identified. However, total variance explained in food use increased as the detail included in the PCA decreased (approximately 8%, 168 items to approximately 17%, 36 items). Conversely, reduced detail in PCA tended to attenuate the odds ratio (OR) associated with the healthy patterns (OR 0.55, 95% confidence interval (CI) 0.35-0.84 and OR 0.77, 95% CI 0.49-1.20, 168 and 36 items, respectively) but not the high-fat patterns (OR 0.95, 95% CI 0.57-1.58 and OR 0.85, 0.51-1.40, 168 and 36 items, respectively). CONCLUSIONS: Greater detail in food-use information may be desirable in determination of dietary patterns for more precise estimates of disease risk.

Diet in the epidemiology of endometrial cancer in western New York (United States).

OBJECTIVES: We examined diet and risk of endometrial cancer among women in the Western New York Diet Study (1986-1991). METHODS: Self-reported frequency of use of 172 foods and beverages during the 2 years before the interview and other relevant data were collected by detailed interviews from 232 endometrial cancer cases and 639 controls, frequency-matched for age and county of residence. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by unconditional logistic regression, adjusting for age, education, body mass index (BMI), smoking history, hypertension, diabetes, age at menarche, parity, oral contraceptive use, menopausal status, menopausal estrogen use, and energy. RESULTS: Risks were reduced for women in the highest quartiles of intake of protein (OR 0.4, 95% CI: 0.2-0.9), dietary fiber (OR 0.5, 95% CI: 0.3-1.0), phytosterols (OR 0.6, 95% CI: 0.3-1.0), vitamin C (OR 0.5, 95% CI: 0.3-0.8) folate (OR 0.4, 95% CI: 0.2-0.7), alpha-carotene (OR 0.6, 95% CI: 0.4-1.0), beta-carotene (OR 0.4, 95% CI: 0.2-0.6), lycopene (OR 0.6, 95% CI: 0.4-1.0), lutein + zeaxanthin (OR 0.3, 95% CI: 0.2-0.5) and vegetables (OR 0.5, 95% CI: 0.3-0.9), but unrelated to energy (OR 0.9, 95% CI: 0.6-1.5) or fat (OR 1.6, 95% CI: 0.7-3.4). CONCLUSIONS: Our results support previous findings of reduced endometrial cancer risks associated with a diet high in plant foods.

Cigarette smoking, N-acetyltransferase 2 genetic polymorphisms, and breast cancer risk.

OBJECTIVE: To determine if N-acetyltransferase 2 (NAT2) polymorphisms result in decreased capacity to detoxify carcinogenic aromatic amines in cigarette smoke, thus making some women who smoke more susceptible to breast cancer. DESIGN: Case-control study with genetic analyses. DNA analyses were performed for 3 polymorphisms accounting for 90% to 95% of the slow acetylation phenotype among whites. SETTING AND PARTICIPANTS: White women with incident primary breast cancer (n=304) and community controls (n=327). RESULTS: Neither smoking nor NAT2 status was independently associated with breast cancer risk. There were no clear patterns of increased risk associated with smoking by NAT2 status among premenopausal women. In postmenopausal women, NAT2 strongly modified the association of smoking with risk. For slow acetylators, current smoking and smoking in the distant past increased breast cancer risk in a dose-dependent manner (odds ratios [95% confidence intervals] for the highest quartile of cigarettes smoked 2 and 20 years previously, 4.4 [1.3-14.8] and 3.9 [1.4-10.8], respectively). Among rapid acetylators, smoking was not associated with increased breast cancer risk. CONCLUSIONS: Our results suggest that smoking may be an important risk factor for breast cancer among postmenopausal women who are slow acetylators, demonstrate heterogeneity in response to carcinogenic exposures, and may explain previous inconsistent findings for cigarette smoking as a breast cancer risk factor.

Premenopausal breast cancer risk and intake of vegetables, fruits, and related nutrients.

BACKGROUND: Given the international variations in breast cancer incidence rates and the changes in breast cancer incidence among migrant populations, it has been hypothesized that diet is a factor influencing risk of this disease. Many studies indicate that a diet high in vegetables and fruits may protect against breast cancer. PURPOSE: We conducted a case-control study of diet, including the intake of non-food supplements, and premenopausal breast cancer risk. We evaluated in detail usual intake of vegetables and fruits (each measured as the total reported grams consumed for all queried vegetables and fruit), vitamins C and E, folic acid, individual carotenoids, and dietary fiber with its components. METHODS: Case patients (n=297) were identified through pathology records from hospitals in Erie and Niagara counties in western New York. They consisted of premenopausal women 40 years of age or oder who were diagnosed with breast cancer from November 1986 through April 1991. Control subjects (n=311), frequency-matched to case patients on the basis of age and county of residence, were randomly selected from New York State Department of Motor Vehicles records. In-person interviews included detailed reports of usual diet in the period 2 years before the interview. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: There was a reduction in risk associated with high intake of several nutrients. With the lowest quartile of intake as the referent, adjusted ORs for the highest quartile of intake for specific nutrients were as follows: vitamin C (OR=0.53; 95% CI=0.33-0.86), alpha-tocopheral (OR=0.55; 95% CI=0.34-0.88), folic acid (OR=0.50; 95% CI=0.31-0.82), alpha-carotene (OR=0.67; 95% CI=0.42-1.08) and beta-carotene (OR=0.46; 95% CI=0.28-0.74), lutein + zeaxanthin (OR=0.47; 95% CI=0.28.0-77), and dietary fiber from vegetables and fruits (OR=0.48; 95% CI=0.30-0.78). No association with risk was found for beta-cryptoxanthin, lycopene, or grain fiber. Fruits were weakly associated with a reduction in risk (fourth quartile OR=0.67; 95% CI=0.42-1.09). No association was found between breast cancer risk and intake of vitamins C and E and folic acid taken as supplements. A strong inverse association between total vegetable intake and risk was observed (fourth quartile OR=0.46; 95% CI=0.28-0.74). This inverse association was found to be independent of vitamin C,alpha-tocopherol, folic acid, dietary fiber, and alpha-carotene. Adjusting for beta-carotene or lutein + zeaxanthin somewhat attenuated the inverse association with vegetable intake. CONCLUSIONS: In this population, intake of vegetables appears to decrease premenopausal breast cancer risk. This effect may be related, in part, to beta-carotene and lutein + zeaxanthin in vegetables. It appears, however, that, of the nutrients and food components examined, no single dietary factor explains the effect. Evaluated components found together in vegetables may have a synergistic effect on breast cancer risk; alternatively, other unmeasured factors in these foods may also influence risk.

Reproducibility of nutrient intake in a food frequency questionnaire used in a general population.

This study evaluates the reproducibility of nutrient intake in a 45-item food frequency questionnaire (FFQ). The FFQ was mailed in 1980 to persons eligible to participate in a large cohort study on diet and cancer risk; a follow-up version with 75 food items was mailed in 1988 to selected original participants. A random sample of 500 men and 500 women from the New York State general population was selected from individuals who responded to both waves of the study. The subjects' 1988 responses were compared with their original 1980 responses; Pearson's correlations ranged from 0.25 for retinol to 0.55 for vitamin C with or without supplements and vitamin E with supplements in women. Reproducibility of nutrient intake in this questionnaire indicates that brief FFQs may be a useful tool to study nutrient intake and chronic disease relationships, although they are subject to substantial measurement error and dietary change.

Cytochrome P4501A1 and glutathione S-transferase (M1) genetic polymorphisms and postmenopausal breast cancer risk.

Polycyclic aromatic hydrocarbons, possible human breast carcinogens, are metabolized by cytochrome P4501A1 (CYP1A1) and glutathione S-transferase (GSTM1). A CYP1A1 polymorphism (isoleucine to valine substitution in exon 7) or the null allele for GSTM1 may affect the mutagenic potential of polycyclic aromatic hydrocarbons. We examined polymorphisms in GSTM1 and CYP1A1 in relation to breast cancer risk. Included were 216 postmenopausal Caucasian women with incident breast cancer and 282 community controls. DNA analyses suggested no increased breast cancer risk with the null GSTM1 genotype [odds ratio (OR) = 1.10; CI, 0.73-1.64], although there was some indication that the null genotype was associated with risk among the youngest postmenopausal women (OR = 2.44; CI, 0.89-6.64). Slightly elevated risk was associated with the CYP1A1 polymorphism (OR = 1.61; CI, 0.94-2.75) and was highest for those who smoked up to 29 pack-years (OR = 5.22; CI, 1.16-23.56). Statistical power to detect an effect may be limited by small numbers, and larger sample sizes would be required to corroborate these suggestive findings.

Reproducibility of food intake in a food frequency questionnaire used in a general population.

This study evaluates the reproducibility of food intake reports in a 45-item self-administered food frequency questionnaire (FFQ) used for a diet study in a large cohort in New York State. The first FFQ was mailed in 1980, and a followup version containing 75 food items was mailed in 1988 to the eligible original participants. Reproducibility was evaluated by comparing the subjects' 1988 responses with their original 1980 responses. Spearman's correlations ranged from 0.27 (nuts other than peanuts) to 0.56 (summer squash) in men and from 0.25 (tomatoes) to 0.51 (summer squash) in women. Analyses stratified by age, education, marital status, body mass index, cigarette smoking, alcohol drinking, and special diet revealed few substantial differences in correlations. The moderate reproducibility of foods in this questionnaire indicates that brief FFQs may be a useful tool to study food intake and chronic disease relationships in this population.