No abstract

Flavonoids, which are found in certain plant foods, are thought to lower cancer risk through their antioxidant, antiestrogenic and antiproliferative properties. We examined the association of intake of total flavonoids and 7 flavonoid subclasses with risk of lung, colorectal, breast, pancreatic and upper aerodigestive cancer among women in a large prospective cohort study. Study participants were 34,708 postmenopausal women in the Iowa Women's Health Study who completed a food frequency questionnaire and were followed for cancer occurrence from 1986 through 2004. Flavonoid intake was estimated from 3 databases developed by the USDA Nutrient Data Laboratory (NDL). Hazard ratios (HR) for cancer risk were calculated across total flavonoid and flavonoid subclass intake categories. Interactions between smoking history and flavonoid intake were also examined. After multivariable adjustment, lung cancer incidence was inversely associated with intakes of flavanones (HR 5 0.68; 95% CI: 0.53-0.86, all results highest vs. lowest quintile) and proanthocyanidins (HR 5 0.75; 95% CI: 0.57-0.97). Among current and past smokers, those with intakes in the highest quintile for flavanones (HR 5 0.66; 95% CI: 0.50-0.86), and proanthocyanidins (HR 5 0.66; 95% CI; 0.49-0.89) had significantly lower lung cancer incidence than those in the lowest quintile. Similar associations were not seen in never smokers. Isoflavone intake was inversely associated with overall cancer incidence (HR 5 0.93, 95% CI: 0.86-1.00). This study provides further support for a beneficial effect of flavonoid intake on lung cancer risk, especially among current and past smokers.

A diet-patterns approach has often been used to describe eating patterns in adults but has rarely been used in adolescents. We used principal components factor analysis to: 1) describe the dietary patterns of a cohort of ethnically diverse youth during early and middle adolescence; 2) examine if the patterns persisted 5 y later; and 3) study secular trends. Project EAT-I (Time 1) collected data on 4746 middle school (younger cohort) and high school (older cohort) students in 31 Minnesota schools in 1998-1999. Project EAT-II (Time 2) resurveyed 53% (n = 2516) of the original cohort in 2003-2004. Dietary intake was assessed at Time 1 and 2 using the Youth/Adolescent FFQ. We identified dietary patterns separately by cohort (older/younger) and gender (boys/girls). At Time 1, we identified 4 patterns in early and middle adolescents that were relatively consistent between boys and girls that we labeled vegetable, fruit, sweet/salty snack food, and starchy food. Longitudinal analyses indicated that patterns were relatively stable over 5 y, with the exception of a new fast food pattern. Examination of age-matched secular trends in middle adolescents (older cohort at Time 1, younger cohort at Time 2) showed similar patterns, with the exception of the fast food pattern that emerged at Time 2 among middle adolescent boys. We identified dietary patterns in this adolescent population that differed from those usually found in adults. Patterns were similar across gender and age cohorts and were relatively similar over time, with the exception a new fast food pattern.

The relationship between dietary intake and obesity is complex, and dietary pattern analysis may offer new insight. We examined associations between dietary patterns identified in a diverse cohort of adolescents and weight status cross-sectionally and over a 5-year period. Project EAT (Eating Among Teens) (Time 1) collected data on 4746 middle (younger cohort) and high school (older cohort) students in 1998 -9. EAT-II (Time 2) resurveyed 2516 of the original cohort in 2003-4. All analyses were run separately by age cohort and sex. The relationship between dietary patterns identified previously (vegetable, fruit, vegetable & fruit, starchy food, sweet & salty snack food, and fast food) and weight status was examined using logistic regression. All analyses were adjusted for socioeconomic status, race/ethnicity and activity level (longitudinal analyses were also adjusted for baseline weight status). In crosssectional analyses, higher adherence to dietary patterns loading heavily on vegetables was associated with lower risk of overweight/ obese weight status in older and younger girls, whereas higher adherence to a 'sweet & salty snack food' pattern was associated with lower risk in older and younger boys. These associations were found prospectively in older boys and girls, but were no longer significant in analyses adjusting for baseline weight status. We did not find consistent or intuitive associations between dietary patterns and weight status. Identified patterns may not capture the elements of diet that are truly important in determining adolescent weight, or diet may not be the primary driver in determining weight status at this age. Methodological difficulties in assessing diet must also be taken into consideration.

Vitamin D, a prosteroid hormone with anti-proliferative and pro-differentiation activity, is thought to act as a cancer chemopreventive agent. This study evaluated the association between vitamin D intake and breast cancer risk among women in a large prospective cohort study. A total of 34,321 postmenopausal women who had completed a questionnaire that included diet and supplement use were followed for breast cancer incidence from 1986 to 2004. Adjusted relative risks (RR) for breast cancer were calculated for dietary, supplemental, and total vitamin D intake among all women. The adjusted RR of breast cancer for women consuming >800 IU/day versus <400 IU/day total vitamin D was 0.89 (95% CI: 0.77-1.03). RRs were stronger among women with negative than positive ER or PR status. The association of high vitamin D intake with breast cancer was strongest in the first 5 years after baseline dietary assessment (RR = 0.66; 95% CI: 0.46-0.94 compared with lowest-intake group), and diminished over time. Changes in vitamin D intake over time might have contributed to the diminished association observed in later years. Vitamin D intake of >800 IU/day appears to be associated with a small decrease in risk of breast cancer among postmenopausal women. Studies evaluating all sources of vitamin D, especially sun exposure, are needed to fully understand the association between vitamin D and breast cancer risk.