Estimated Daily Lactose Consumption in Healthy U.S. Adults in Relation to Lactase Persistence Genotype (rs4988235)

Lactase persistence (LP), a heritable trait in which lactose can be digested throughout adulthood, is often used to predict dairy intake. However, it is currently unknown how LP relates to daily lactose consumption in healthy US adults. The objective of the study was to estimate lactose from foods reported in the Automated Self-Administered 24-Hour Dietary Assessment Tool (ASA24) and to compare lactose and total dairy consumption in relation to LP genotypes. ASA24 dietary data were collected from healthy Caucasians and Hispanics (n = 215) genotyped for the lactase persistence SNP ID: rs4988235. ASA24 outputs servings of dairy but not the nutrient lactose. Lactose was estimated by matching ASA24-reported foods to foods in the Nutrition Coordinating Center Food and Nutrient Database, which outputs lactose. Analysis of covariance was used to identify whether genotype influenced lactose and total dairy consumption with total energy intake and weight as covariates. Pairwise testing was conducted on the adjusted means using the Tukey adjustment to correct for multiple testing. Median lactose consumption for subjects with the AA genotype (homozygous LP) was 12.08 g (min: 0.91 g, max: 81.85 g), 10.05 g (min: 0.46 g, max: 45.82) for subjects with the AG genotype (heterozygous LP), and 8.97 g (min: 0.47, max: 38.96 g) for subjects with the GG genotype (homozygous lactase non-persistent). AA subjects consumed more lactose than GG subjects (P = 0.024). When stratifying by sex, there were no significant differences among genotypes in women, although GG women consumed the least amount of lactose compared to AA and AG women. AA men consumed more lactose than AG (P = 0.028) and GG men (P = 0.032). Subjects with the AA genotype consumed the most, and GG subjects the least amount of dairy. However, there were no significant differences in total dairy consumption among genotypes. The median amount of lactose consumed daily by healthy adults is 9–12 g/day, with higher consumption by those with an LP genotype. Total dairy intake was not significantly influenced by genotype, highlighting the value in specifically estimating lactose consumption. Maximal lactose intake by lactase non-persisters exceeding 15 g/day suggests alternate routes of lactose catabolism. The California Dairy Research Foundation and the USDA-ARS.