The SLC23A1 rs6596473 variant was associated with reduced vitamin C absorption into systemic circulation in the overall population; however, among individuals with suboptimal serum vitamin C status, it was associated with beneficial gut microbial profiles.
GG carriers of SLC23A1 rs6596473 had significantly higher odds of suboptimal serum vitamin C status compared to CC carriers.
Among individuals with suboptimal serum vitamin C status, GG carriers exhibited distinct gut microbial community structures with elevated richness and evenness compared to CC and CG carriers.
GG carriers with suboptimal serum vitamin C status had higher abundances of Bifidobacterium compared to CC and CG carriers.
GG carriers with suboptimal serum vitamin C status had higher abundances of Ruminococcaceae incertae sedis compared to both CC and CG carriers.
GG carriers with suboptimal serum vitamin C status had higher serum concentrations of propionate and butyrate compared to CC and CG carriers.
The study findings suggest that the SLC23A1 rs6596473 genetic variant has complex health effects extending beyond circulating vitamin C levels to gut microbial ecology.
This research suggests that a genetic variant in a vitamin C transporter gene (SLC23A1 rs6596473) affects both how much vitamin C reaches the bloodstream and the composition of gut bacteria. In a group of 257 healthy Korean adults, people who carried two copies of the less common 'G' version of this gene variant (GG genotype) were about 2.65 times more likely to have low blood vitamin C levels compared to those with two copies of the more common 'C' version. This makes sense because the gene encodes a protein that helps transport vitamin C from the intestine into the body, and the G variant appears to reduce this absorption. However, among the 43 participants who already had low blood vitamin C, those with the GG genotype showed a surprising pattern in their gut microbiomes. They had greater diversity of gut bacteria, along with higher levels of potentially beneficial bacteria like Bifidobacterium and Ruminococcaceae. These GG carriers also had higher blood levels of propionate and butyrate — short-chain fatty acids produced by gut bacteria that are associated with gut and metabolic health. This suggests that when vitamin C is not efficiently absorbed into the bloodstream, more of it may remain in the intestine where it can support the growth of beneficial bacteria. This research suggests that the same genetic variant can have seemingly opposite effects: reducing the vitamin C available to the rest of the body while potentially fostering a healthier gut environment. The findings point toward the possibility that genetic information about vitamin C transport could one day be used to personalize nutritional recommendations, though the cross-sectional design of this study means cause-and-effect relationships cannot be established and further research is needed.
Sim M, Hwang G, Shin D, Jeong Y. (2026). Associations of solute carrier family 23 member 1 (SLC23A1) rs6596473 genetic variant with serum vitamin C status and gut microbial profiles in healthy adults: A cross-sectional study.. Clinical nutrition (Edinburgh, Scotland). https://doi.org/10.1016/j.clnu.2026.106669