Fat and meat intake and prostate cancer risk: the multiethnic cohort study

Dietary fat and meat as potential risk factors for prostate cancer have been the focus of many epidemiologic investigations, and findings from recent studies in particular have been inconsistent. Therefore, we examined the association between these exposures and prostate cancer risk in the Multiethnic Cohort Study. The analyses included 82,483 men in Hawaii and Los Angeles aged >or=45, who completed a detailed quantitative food frequency questionnaire in 1993-1996. During the follow-up period of 8 years, a total of 4,404 incident cases, including 1,278 nonlocalized or high-grade cancer cases, were identified. Cox proportional hazard models were used to estimate relative risks of prostate cancer after adjustment for time on study, ethnicity, family history of prostate cancer, education, body mass index, smoking status and energy intake. Intake of different types of fat (total, saturated, monounsaturated or polyunsaturated), n-6 fatty acid, cholesterol, various meats, and fats from meat showed no association with overall prostate cancer risk or with nonlocalized or high-grade prostate cancer. Furthermore, we found little evidence of any relation of fat and meat intake with prostate cancer risk within any of the 4 racial/ethnic groups (African Americans, Japanese Americans, Latinos and Whites). There was a suggestion of a protective effect of n-3 fatty acid intake that was limited to Latinos and Whites. However, overall, our findings from a large cohort study of ethnically diverse population give no indication that intake of fat and meat substantially affects prostate cancer risk.     

Genetic variation at the CYP19A1 locus predicts circulating estrogen levels but not breast cancer risk in postmenopausal women

The CYP19A1 gene encodes the enzyme aromatase, which is responsible for the final step in the biosynthesis of estrogens. In this study, we used a systematic two-step approach that included gene resequencing and a haplotype-based analysis to comprehensively survey common genetic variation across the CYP19A1 locus in relation to circulating postmenopausal steroid hormone levels and breast cancer risk. This study was conducted among 5,356 invasive breast cancer cases and 7,129 controls comprised primarily of White women of European descent drawn from five large prospective cohorts within the National Cancer Institute Breast and Prostate Cancer Cohort Consortium. A high-density single-nucleotide polymorphism (SNP) map of 103 common SNPs (> or =5% frequency) was used to identify the linkage disequilibrium and haplotype patterns across the CYP19A1 locus, and 19 haplotype-tagging SNPs were selected to provide high predictability of the common haplotype patterns. We found haplotype-tagging SNPs and common haplotypes spanning the coding and proximal 5' region of CYP19A1 to be significantly associated with a 10% to 20% increase in endogenous estrogen levels in postmenopausal women [effect per copy of the two-SNP haplotype rs749292-rs727479 (A-A) versus noncarriers; P = 4.4 x 10(-15)]. No significant associations were observed, however, with these SNPs or common haplotypes and breast cancer risk. Thus, although genetic variation in CYP19A1 produces measurable differences in estrogen levels among postmenopausal women, the magnitude of the change was insufficient to contribute detectably to breast cancer.     

Diabetes Incidence Based on Linkages With Health Plans: The Multiethnic Cohort

OBJECTIVE

Using the Hawaii component of the Multiethnic Cohort (MEC), we estimated diabetes incidence among Caucasians, Japanese Americans, and Native Hawaiians.

RESEARCH DESIGN AND METHODS

After excluding subjects who reported diabetes at baseline or had missing values, 93,860 cohort members were part of this analysis. New case subjects were identified through a follow-up questionnaire (1999–2000), a medication questionnaire (2003–2006), and linkage with two major health plans (2007). We computed age-standardized incidence rates and estimated hazard ratios (HRs) for ethnicity, BMI, education, and combined effects of these variables using Cox regression analysis.

RESULTS

After a total follow-up time of 1,119,224 person-years, 11,838 incident diabetic case subjects were identified with an annual incidence rate of 10.4 per 1,000 person-years. Native Hawaiians had the highest rate with 15.5, followed by Japanese Americans with 12.5, and Caucasians with 5.8 per 1,000 person-years; the adjusted HRs were 2.65 for Japanese Americans and 1.93 for Native Hawaiians. BMI was positively related to incidence in all ethnic groups. Compared with the lowest category, the respective HRs for BMIs of 22.0–24.9, 25.0–29.9, and ≥30.0 kg/m² were 2.10, 4.12, and 9.48. However, the risk was highest for Japanese Americans and intermediate for Native Hawaiians in each BMI category. Educational achievement showed an inverse association with diabetes risk, but the protective effect was limited to Caucasians.

CONCLUSIONS

Within this multiethnic population, diabetes incidence was twofold higher in Japanese Americans and Native Hawaiians than in Caucasians. The significant interaction of ethnicity with BMI and education suggests ethnic differences in diabetes etiology.Based on prevalence studies, type 2 diabetes is considerably more common among individuals with ethnic backgrounds other than Caucasian (1–3). Both diabetes and obesity are highly prevalent among Native Hawaiians (4,5), but Japanese Americans also suffer a disproportionate rate of the disease despite their relatively low body weight (6,7). This might be due to the higher proportion of body fat and the larger amount of visceral adipose tissue in Asians compared with Caucasians (8–10). In particular, the visceral fat component appears to be associated with impaired glucose tolerance (11,12) and development of type 2 diabetes (13). Incidence data on type 2 diabetes are limited because of the lack of population-based registries, but health plans store information for large parts of the population (14,15). The Hawaii component of the Multiethnic Cohort (MEC) study (16) offers the opportunity to study diabetes incidence by ethnicity. The cohort, with more than 44,000 Japanese Americans, 14,000 Native Hawaiians, and 35,000 Caucasians in Hawaii, has been followed for more than 10 years. To estimate annual incidence rates for type 2 diabetes since cohort entry, we combined information from MEC follow-up questionnaires with data from diabetes care registries maintained by the two major health plans in Hawaii that capture at least 90% of the population: the Blue Cross and Blue Shield (BCBS) association and Kaiser Permanente Hawaii (KP) (17). Our goal was to estimate incidence rates by sex, ethnicity, age at cohort entry, BMI, and education.     

Dietary fiber and colorectal cancer risk: the multiethnic cohort study

OBJECTIVE: To investigate the association of dietary fiber with colorectal cancer METHODS: A total of 85,903 men and 105,108 women completed a quantitative food frequency questionnaire in 1993-1996. A total of 1,138 men and 972 women were subsequently diagnosed with adenocarcinoma of the large bowel. Cox proportional hazards models were used to calculate multivariate adjusted relative risks (RR) and 95% confidence intervals (95% CI) for colorectal cancer. RESULTS: High consumers of dietary fiber were more active, less overweight, and less likely to be cigarette smokers than low consumers in both sexes. Fiber was inversely associated with colorectal cancer risk after adjustment for age and ethnicity in men (RR = 0.49; 95% CI, 0.41-0.60, highest vs. lowest quintile) and women (RR = 0.75; 95% CI, 0.61-0.92). After further adjustment for lifestyle and dietary factors, the inverse association remained significant in men (RR = 0.62; 95% CI, 0.48-0.79), but not in women (RR = 0.88; 95% CI, 0.67-1.14). Adjustment for the combination of replacement hormone use with either cigarette smoking or body mass index accounted for the lack of association with fiber in women. CONCLUSION: Dietary fiber was inversely associated with colorectal cancer risk in men, but its relation to replacement hormone use and other factors affected its inverse association in women.     

Adherence to recommendations for fruit and vegetable intake,ethnicity and ischemic heart disease mortality

Background and aimsIschemic heart disease (IHD) accounts for one-third of annual deaths in the U.S. and mortality rates vary by ethnicity. The association between adherence to dietary guidelines for fruit and vegetable intake with IHD mortality among different ethnic groups has not previously been examined.Methods and resultsA prospective cohort design was used to examine the incidence of fatal IHD among participants in the Multiethnic Cohort Study. Participants included 164,617 men and women from five ethnic groups: African American, Native Hawaiian, Japanese American, Latino, and Caucasian. Cox proportional hazards models, stratified by ethnicity and sex, were used to examine associations between adherence with recommended dietary guidelines for fruit and vegetable intake and risk for fatal IHD. The results did not provide evidence that the association between adherence with dietary recommendations for fruit or vegetable intake and IHD mortality varies by ethnicity. Pooled data did provide evidence that adhering to the recommendations for vegetables lowered risk among men (RR = 0.84, 95% CI: 0.74–0.96) and women (RR = 0.80, 95% CI: 0.69–0.94). No significant effects were observed for fruit intake.ConclusionsThe effect of dietary intake of fruit and vegetables did not vary by ethnicity, providing evidence that recommendations do not need to be individualized for these special populations. The protective effect observed for vegetable intake among both sexes confirms previous findings and supports the evidence base for promoting diet modification in this direction.     

Dietary Fiber Intake and Endogenous Serum Hormone Levels in Naturally Postmenopausal Mexican American Women: The Multiethnic Cohort Study

This study investigated dietary fiber intake in association with serum estrogen levels in naturally postmenopausal Latina women with a wide range of fiber intake. Estrone (E₁), estradiol (E₂), and sex-hormone-binding globulin (SHBG) were measured in 242 women. Associations between estrogen levels and intake of dietary fiber, including insoluble and soluble fractions, quantified from a food frequency questionnaire, were examined. The biomarker enterolactone was also measured. After adjustment for age, weight, and other nondietary factors, dietary fiber intake was inversely associated with E₁ and E₂; there was a 22% and 17% decrease (2P _trend = 0.023 and 0.045) among subjects in the highest quintile of intake compared with the lowest. Fitting dietary fiber together with soluble and insoluble nonstarch polysaccharides (NSP) showed a much greater decrease in E₁ and E₂ (47% and 41%, respectively) while increased soluble NSP intake showed increases in E₁ and E₂ (64% and 69%, respectively). Two foods, avocado and grapefruit, showed significant positive associations with E ₁ (2P _trend = 0.029 and 0.015, respectively). This study suggests that different components of dietary fiber may have very significant different effects on serum estrogen levels. The suggestive findings relating increased estrogen levels to avocado and grapefruit intakes need confirmation.     

Lifestyle and Dietary Correlates of Plasma Insulin-Like Growth Factor Binding Protein-1 (IGFBP-1), Leptin,and C-Peptide: The Multiethnic Cohort

Circulating insulin-like growth factor binding protein 1 (IGFBP-1), leptin, and insulin are 3 proteins modified by obesity and have been associated with cancer at several sites in past studies. We conducted a cross-sectional study to describe the correlation of these proteins with gender, race/ethnicity, anthropometric indexes, and dietary and lifestyle factors. We measured fasting plasma levels of IGFBP-1, leptin, and C-peptide, used here as a stable measure of insulin secretion, in a random sample of 450 male and 352 postmenopausal female Hawaii and Los Angeles Multiethnic Cohort Study (MEC) participants (age range 47–82 yr at blood draw). Through a series of multiple linear regressions, we found that the most parsimonious model for plasma IGFBP-1 included inverse associations with age, body mass index (BMI), and regular soda intake. A term for interaction between age and BMI was positively associated with plasma IGFBP-1. Adjusted mean plasma leptins were highest among Whites and African Americans and lowest among Hawaiians and Japanese Leptin was also inversely associated with age and positively associated with the interaction between age and race/ethnicity, female gender, and BMI. A model with only race/ethnicity and BMI (positive association) was best for plasma C-peptide. Adjusted means for C-peptide were highest for Japanese and Whites and lowest for African Americans. The overall percent of variance in protein levels explained by these models was low for IGFBP-1(R² = 0.17) and C-peptide (R² = 0.11) and higher for leptin (R² = 0.57). We saw no clear correlation between racial/ethnic trends in protein levels with those of colorectal, breast, or prostate cancer incidence rates in the MEC. Research to clarify factors associated with determination of these proteins and their relationship with cancer etiology is warranted.     

Menstrual and reproductive factors and risk of breast cancer in Asian-Americans.

We conducted a population-based case-control study of breast cancer among Chinese-, Japanese- and Filipino-American women in Los Angeles County Metropolitan Statistical Area (MSA), San Francisco-Oakland MSA and Oahu, Hawaii. One objective of the study was to quantify breast cancer risks in relation to menstrual and reproductive histories in migrant and US-born Asian-Americans and to establish whether the gradient of risk in Asian-Americans can be explained by these factors. Using a common study design and questionnaire in the three study areas, we successfully conducted in-person interviews with 597 Asian-American women diagnosed with incident, primary breast cancer during the period 1983-87 (70% of those eligible) and 966 population-based controls (75% of those eligible). Controls were matched to cases on age, ethnicity and area of residence. In the present analysis, which included 492 cases and 768 controls, we observed a statistically non-significant 4% reduction in risk of breast cancer with each year delay in onset of menstruation. Independent of age at menarche risk of breast cancer was lower (odds ratio; OR=0.77) among women with menstrual cycles greater than 29 days. Parous Asian-American women showed a significantly lower risk of breast cancer then nulliparous women (OR=0.54). An increasing number of livebirths and a decreasing age at first livebirth were both associated with a lower risk of breast cancer, although the effect of number of livebirths was no longer significant after adjustment for age at first livebirth. Women with a pregnancy (spontaneous or induced abortions) but no livebirth had a statistically non-significant increased risk (OR=1.84), but there was no evidence that one type of abortion was particularly harmful. A positive history of breastfeeding was associated with non-significantly lower risk of breast cancer (OR=.78). There are several notable differences in the menstrual and reproductive factors between Asian-Americans in this study and published data on US whites. US-born Asian Americans had an average age at menarche of 12.12 years-no older than has been found in comparable studies of US whites, but 1.4 years earlier than Asian women who migrated to the US. Asian-American women, particularly those born in the US and those who migrated before age 36, also had a later age at first birth and fewer livebirths than US whites. A slightly higher proportion of Asian-American women breastfed, compared with US whites. The duration of breastfeeding was similar in US-born Asians and US whites, but was longer in Asian migrants, especially those who migrated at a later age. Menstrual and reproductive factors in Asian-American women are consistent with their breast cancer rates being at least as high as in US whites, and they are. However, the effects of these menstrual and reproductive factors were small and the ORs for migration variables changed only slightly after adjustment for these menstrual and reproductive factors. These results suggest that the lower rates of breast cancer in Asians must be largely as a result of other environmental/lifestyle factors.