(P11-003-24) Associations Between Plant-Based Diet Indices and Plasma and Urinary Biomarkers in the Cancer Prevention Study-3 Dietary Assessment Sub-study

Objectives: The objective of this study was to evaluate associations of the Overall Plant-based Diet Index (PDI), Healthful Plant-based Diet Index (hPDI), and Unhealthful Plant-based Diet Index (uPDI) with blood and urine biomarkers in a large, geographically and ethnically diverse cohort.

Methods: Participants were n=677 adults in the 2015-2016 Cancer Prevention 3 Dietary Assessment Sub-study (CPS-3 DAS). Each completed a 191-item, CPS-3 Food Frequency Questionnaire (FFQ), ≤ six 24-hour dietary recalls (24HRs), and provided two fasted blood samples (men, n=235; women, n=419) and urine samples (men, n=183; women, n=312). PDI, hPDI, and uPDI were calculated using energy-adjusted, food group intakes (svg/d) from the FFQ and mean 24HRs. Biomarkers (urine: total potassium (mg), total protein (g), total sodium (mg); plasma (µg/L): α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein + zeaxanthin, retinol) were averaged across the two timepoints and log-transformed. Spearman partial correlations were used to correlate PDI, hPDI, and uPDI with biomarkers and were deattenuated to account for between-person variability in biomarker timepoints, controlling for BMI, age, smoking status, and supplement use. For carotenoids and retinol, serum total cholesterol was additionally adjusted. Analyses were also stratified by race.

Results: hPDI and uPDI were more frequently correlated with biomarkers compared to PDI. Biomarkers common in plant foods, such as carotenoids and potassium, were positively associated (r_s: ≥ 0.20) with hPDI and in some cases PDI and were inversely associated (r_s: –0.20) with uPDI. We observed inverse associations (r_s ≤ –0.20) between protein and PDI and uPDI and between sodium and PDI and hPDI. Diet indices correlations with carotenoids tended to be stronger among African Americans (r_s: –0.40-0.61) compared to Whites (r_s: –0.31-0.38) and Hispanic/Latinos (r_s: –0.50-0.31). All other trends were similar across sex and race and between the FFQ and 24HRs.

Conclusions: We observed several consistent associations between PDI, hPDI, and/or uPDI and blood and urine biomarkers in CPS-3 DAS. Among plant-based diet indices, hPDI and uPDI may be preferable to PDI for comparison among nutritional biomarkers.

Funding Sources: American Cancer Society (ACS)