Reproducibility and Validity of Plant-Based Dietary Indices in the Cancer Prevention Study-3 Diet Assessment Substudy

Area of Science:

• Nutritional Epidemiology
• Dietary Assessment Methodology

Background:

• The Overall Plant-based Diet Index (PDI), Healthful Plant-based Diet Index (hPDI), and Unhealthful Plant-based Diet Index (uPDI) are emerging tools for assessing plant-based dietary patterns.
• Previous assessments of their reproducibility and validity have been limited across diverse populations.

Purpose of the Study:

• To evaluate the reproducibility and validity of the PDI, hPDI, and uPDI.
• To assess these indices in a racially and ethnically diverse cohort.

Main Methods:

• Utilized data from the Cancer Prevention Study 3 Dietary Assessment Substudy (CPS-3 DAS).
• Participants completed two Food Frequency Questionnaires (FFQs) and multiple 24-hour dietary recalls (24HRs).
• Calculated plant-based diet scores and assessed reproducibility (FFQ vs. FFQ) and validity (FFQ vs. 24HRs and biomarkers) using Pearson correlations.

Main Results:

• Reproducibility correlations between FFQs ranged from 0.64 to 0.85 for men and 0.66 to 0.80 for women.
• Validity correlations between FFQ2 and mean 24HRs ranged from 0.49 to 0.68.
• Moderate to good reproducibility and validity were observed across racial/ethnic subgroups, with the highest in non-Hispanic White adults.

Conclusions:

• The PDI, hPDI, and uPDI demonstrate good reproducibility and moderate-to-good validity when used with the CPS-3 Food Frequency Questionnaire.
• Further validation across diverse populations and dietary assessment tools is recommended.