rs33972313

rs33972313 is a missense variant in SLC23A1, the gene encoding SVCT1, the principal sodium-dependent intestinal/renal transporter for L-ascorbic acid (vitamin C); the minor allele produces a valine-to-methionine substitution in the transporter protein (confirmed via Ensembl VEP transcript annotation). In pooled analyses of more than 15,000 participants, each copy of the minor allele was associated with roughly 6 micromol/L lower circulating vitamin C concentration, consistent with reports that the variant transporter is markedly less efficient at ascorbic acid uptake. It is used as a marker of genetically lower baseline vitamin C transport/status, independent of dietary intake.