Supplementary Material for: Body Mass Index and Interindividual Variation in Salivary Amylase Gene Copy Number Assessed Using an In-House Validated Method: A Pilot Study from the National Nutrition Survey of a High Rice-Consuming Nation

Introduction: The AMY1 gene, which encodes salivary amylase, exhibits copy number variation (CNV) that affects starch metabolism and may influence obesity risk. This study aimed to assess AMY1 CNV among selected participants of the 2018-2019 Expanded National Nutrition Survey (ENNS), using a validated digital PCR (dPCR) method.
Methodology: The method validation was initially performed using certified reference material. Whole blood DNA was isolated from selected nutrition survey respondents who had available daily rice intake data. The daily rice intake of participants was divided into tertiles. chi-square tests was used to compare AMY1 CNV, age, BMI, smoking and alcohol status, and other variables across daily rice intake tertiles.
Results: Data from selected ENNS participants revealed AMY1 CNV ranging from 6–18 copies. Higher rice intake was significantly associated with increased AMY1 CNV (p = 0.035). Lower AMY1 CNV was more prevalent among overweight and obese individuals.
Conclusion: Findings highlight gene-diet interactions and support the relevance of personalized nutrition approaches in the Philippines.