Food predictors of plasma carotenoids

Empirical prediction models that weight food frequency questionnaire (FFQ) food items by their relation to nutrient biomarker concentrations may estimate nutrient exposure better than nutrient intakes derived from food composition databases. Carotenoids may especially benefit because contributing foods vary in bioavailability and assessment validity. Our objective was to develop empirical prediction models for the major plasma carotenoids and total carotenoids and evaluate their validity compared with dietary intakes calculated from standard food composition tables. 4180 nonsmoking women in the Nurses’ Health Study (NHS) blood subcohort with previously measured plasma carotenoids were randomly divided into training (n = 2787) and testing (n = 1393) subsets. Empirical prediction models were developed in the training subset by stepwise selection from foods contributing ≥0.5% to intake of the relevant carotenoid. Spearman correlations between predicted and measured plasma concentrations were compared to Spearman correlations between dietary intake and measured plasma concentrations for each carotenoid. Three to 12 foods were selected for the α-carotene, β-carotene, β-cryptoxanthin, lutein/zeaxanthin, lycopene, and total carotenoids prediction models. In the testing subset, Spearman correlations with measured plasma concentrations for the calculated dietary intakes and predicted plasma concentrations, respectively, were 0.31 and 0.37 for α-carotene, 0.29 and 0.31 for β-carotene, 0.36 and 0.41 for β-cryptoxanthin, 0.28 and 0.31 for lutein/zeaxanthin, 0.22 and 0.23 for lycopene, and 0.22 and 0.27 for total carotenoids. Empirical prediction models may modestly improve assessment of some carotenoids, particularly α-carotene and β-cryptoxanthin.

Plasma carotenoid- and retinol-weighted multi-SNP scores and risk of breast cancer in the National Cancer Institute Breast and Prostate Cancer Cohort Consortium

BACKGROUND

Dietary and circulating carotenoids have been inversely associated with breast cancer risk, but observed associations may be due to confounding. Single-nucleotide polymorphisms (SNPs) in β-carotene 15,15'-monooxygenase 1 (BCMO1), a gene encoding the enzyme involved in the first step of synthesizing vitamin A from dietary carotenoids, have been associated with circulating carotenoid concentrations and may serve as unconfounded surrogates for those biomarkers. We determined associations between variants in BCMO1 and breast cancer risk in a large cohort consortium.

METHODS

We used unconditional logistic regression to test four SNPs in BCMO1 for associations with breast cancer risk in 9,226 cases and 10,420 controls from the National Cancer Institute Breast and Prostate Cancer Cohort Consortium (BPC3). We also tested weighted multi-SNP scores composed of the two SNPs with strong, confirmed associations with circulating carotenoid concentrations.

RESULTS

Neither the individual SNPs nor the weighted multi-SNP scores were associated with breast cancer risk [OR (95% confidence interval) comparing extreme quintiles of weighted multi-SNP scores = 1.04 (0.94-1.16) for β-carotene, 1.08 (0.98-1.20) for α-carotene, 1.04 (0.94-1.16) for β-cryptoxanthin, 0.95 (0.87-1.05) for lutein/zeaxanthin, and 0.92 (0.83-1.02) for retinol]. Furthermore, no associations were observed when stratifying by estrogen receptor status, but power was limited.

CONCLUSIONS

Our results do not support an association between SNPs associated with circulating carotenoid concentrations and breast cancer risk.

IMPACT

Future studies will need additional genetic surrogates and/or sample sizes at least three times larger to contribute evidence of a causal link between carotenoids and breast cancer.

Circulating carotenoids and risk of breast cancer: pooled analysis of eight prospective studies

BACKGROUND

Carotenoids, micronutrients in fruits and vegetables, may reduce breast cancer risk. Most, but not all, past studies of circulating carotenoids and breast cancer have found an inverse association with at least one carotenoid, although the specific carotenoid has varied across studies.

METHODS

We conducted a pooled analysis of eight cohort studies comprising more than 80% of the world's published prospective data on plasma or serum carotenoids and breast cancer, including 3055 case subjects and 3956 matched control subjects. To account for laboratory differences and examine population differences across studies, we recalibrated participant carotenoid levels to a common standard by reassaying 20 plasma or serum samples from each cohort together at the same laboratory. Using conditional logistic regression, adjusting for several breast cancer risk factors, we calculated relative risks (RRs) and 95% confidence intervals (CIs) using quintiles defined among the control subjects from all studies. All P values are two-sided.

RESULTS

Statistically significant inverse associations with breast cancer were observed for α-carotene (top vs bottom quintile RR = 0.87, 95% CI = 0.71 to 1.05, P(trend) = .04), β-carotene (RR = 0.83, 95% CI = 0.70 to 0.98, P(trend) = .02), lutein+zeaxanthin (RR = 0.84, 95% CI = 0.70 to 1.01, P(trend) = .05), lycopene (RR = 0.78, 95% CI = 0.62 to 0.99, P(trend) = .02), and total carotenoids (RR = 0.81, 95% CI = 0.68 to 0.96, P(trend) = .01). β-Cryptoxanthin was not statistically significantly associated with risk. Tests for heterogeneity across studies were not statistically significant. For several carotenoids, associations appeared stronger for estrogen receptor negative (ER(-)) than for ER(+) tumors (eg, β-carotene: ER(-): top vs bottom quintile RR = 0.52, 95% CI = 0.36 to 0.77, P(trend) = .001; ER(+): RR = 0.83, 95% CI = 0.66 to 1.04, P(trend) = .06; P(heterogeneity) = .01).

CONCLUSIONS

This comprehensive prospective analysis suggests women with higher circulating levels of α-carotene, β-carotene, lutein+zeaxanthin, lycopene, and total carotenoids may be at reduced risk of breast cancer.

β-Carotene 15,15'-monooxygenase 1 single nucleotide polymorphisms in relation to plasma carotenoid and retinol concentrations in women of European descent

BACKGROUND

Carotenoids have been hypothesized to reduce the risk of many diseases, but associations with intakes or blood concentrations may arise from other constituents of fruit and vegetables. Use of genetic variation in β-carotene 15,15'-monooxygenase 1 (BCMO1), a key enzyme in provitamin A carotenoid metabolism, as a surrogate for carotenoid exposure may aid in determining the role of carotenoids unconfounded by other carotenoid-containing food constituents, but important variants must be identified.

OBJECTIVE

Our goal was to select BCMO1 single nucleotide polymorphisms (SNPs) that predict plasma carotenoid concentrations for use in future epidemiologic studies.

DESIGN

We assessed the associations between 224 SNPs in BCMO1 ± 20 kb imputed from the 1000 Genomes Project EUR reference panel with plasma carotenoid and retinol concentrations by using 7 case-control data sets (n = 2344) within the Nurses' Health Study, randomly divided into training (n = 1563) and testing (n = 781) data sets. SNPs were chosen in the training data set through stepwise selection in multivariate linear regression models; β-coefficients were used as weights in weighted gene scores.

RESULTS

Two or 3 SNPs were selected as predictors of β-carotene, α-carotene, β-cryptoxanthin, and lutein/zeaxanthin. In the testing data set, the weighted gene scores were significantly associated with plasma concentrations of the corresponding carotenoid (P = 6.4 × 10⁻¹², 3.3 × 10⁻³, 0.02, and 1.8 × 10⁻¹⁷, respectively), and concentrations differed by 48%, 15%, 15%, and 36%, respectively, across extreme score quintiles.

CONCLUSIONS

SNPs in BCMO1 are associated with plasma carotenoid concentrations. Given adequate sample size, the gene scores may be useful surrogates for carotenoid exposure in future studies.

Abstract A90: Plasma carotenoids and risk of breast cancer: Pooled analysis of eight prospective cohorts

Carotenoids, prominent micronutrients in fruits and vegetables that act as antioxidants, may reduce the risk of breast cancer. Several studies of plasma carotenoids and breast cancer have been conducted and most, but not all, have found an inverse association with at least one carotenoid although the specific carotenoid has varied across studies. We conducted a pooled analysis of eight cohort studies comprising >95% of the world's published prospective data on plasma carotenoids and breast cancer. The studies included 3,055 cases and 3,955 matched controls from the Columbia Missouri Breast Cancer Serum Bank; MSP/VIP/MONICA cohorts in Umea, Sweden; Johns Hopkins University CLUE I and II; Nurses’ Health Study; Women's Health Study; New York University Women's Health Study; Shanghai Women's Health Study; and Multiethnic Cohort Study. To account for laboratory differences and examine population differences across studies, we recalibrated participant carotenoid levels by re-assaying 20 plasma samples from each cohort together at the same laboratory. Recalibration data are currently available for seven of the eight cohorts; recalibration data from the 8th cohort are being incorporated. Using conditional logistic regression, adjusted for several breast cancer risk factors, we first calculated relative risks (RRs) and 95% confidence intervals (CIs) from each study, using study-specific quintiles, and pooled the estimates using a random effects model weighted by the inverse variances. Next we recalibrated carotenoid levels from each study to a common standard and conducted conditional logistic regression on the pooled data using quintiles defined among the controls from all studies. Levels of carotenoids differed across cohorts (e.g., median recalibrated lycopene ranged from 17.9 (Umea) to 41.9 (NHS) μg/dL) as did the primary contributor to total carotenoids (ß-carotene, lutein/zeaxanthin, or lycopene). Total carotenoids were suggestively inversely associated with breast cancer risk when study-specific RRs were pooled (top vs. bottom study-specific quintile RR=0.72,95% CI (0.51 −1.01), p-trend=0.07), but with significant heterogeneity across studies (p=0.002). Using recalibrated carotenoid levels and common quintiles, significant inverse associations with breast cancer were observed for α-carotene (top vs. bottom common quintile RR=0.82,95% CI (0.68-0.99), p-trend=0.01), ß-carotene (comparable RR=0.75,95% CI (0.62-0.90), p-trend=0.002), lutein/zeaxanthin (comparable RR=0.80,95% CI (0.67-0.97), p-trend=0.03), and total carotenoids (comparable RR=0.79,95% CI (0.65-0.97), p-trend=0.01). ß-cryptoxanthin (comparable RR=0.93,95% CI (0.76-1.13), p-trend=0.07) and lycopene (comparable RR=0.91,95% CI (0.74-1.12), p-trend=0.18) were not significantly associated with breast cancer risk. Tests for heterogeneity using recalibrated data were not significant. This comprehensive prospective analysis suggests women with higher plasma levels of a-carotene, ß-carotene, lutein/zeaxanthin, and total carotenoids may be at reduced risk of breast cancer.

Citation Information: Cancer Prev Res 2010;3(12 Suppl):A90.

No acute effects of grape juice on appetite, implicit memory and mood

Background

Animal experiments document effects of grape juice on cognitive performance and motor skills, and observational studies in humans suggest an inverse association between flavonoid intake and cognitive decline. These effects may be related to the antioxidant properties of polyphenols. Juice consumption and flavonoid intake may also affect appetite.

Objective

To study the acute effects of grape juice consumption on appetite, mood and implicit memory during a time of increased lethargy – the post-lunch dip.

Design

Thirty-five participants with a mean age of 26 years who smoked a mean of 11 cigarettes/day for 8 years were included in the study. It included a practice session and two treatment sessions. All sessions involved consumption of grape juice or an energy-matched placebo with lunch followed by assessments of mood, implicit memory, appetite and food intake.

Results

Mood decreased over time for both treatments, but there were no differences after lunch between grape juice and placebo for any measure.

Conclusion

This study did not document any acute effects of grape juice consumption on mood, implicit memory, appetite or food intake in smokers.