Abstract
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.
Highlights
Food frequency questionnaires (FFQ) are often used to assess usual dietary intake in epidemiologic studies
The empirical prediction models for plasma carotenoids we developed with FFQ food items included foods expected to be major predictors of the individual carotenoids and some foods likely selected by chance or dietary patterns
Based on percent of variation in plasma concentrations explained in the training subset, raw carrots were most predictive of plasma α- and β-carotene and total carotenoids
Summary
Food frequency questionnaires (FFQ) are often used to assess usual dietary intake in epidemiologic studies. An individual’s nutrient intake determined this way may not adequately represent their internal dose, which is often more etiologically-relevant. This potential inadequacy may be due to factors such as responder interpretation of the FFQ; nutrient content data inaccuracy; individual differences in absorption, metabolism, or other physiologic or lifestyle factors; and nutrient bioavailability [2]. An alternative method is to utilize empirical prediction models that weight foods by their relation to biological nutrient (biomarker) levels, such as plasma concentrations [2] This method reduces error from inaccurate food composition data, bioavailability differences among foods, and variation in the validity of questions on individual foods. The impact may vary across studies because the precision of the empirical weights and degree of random error depends on sample size
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