rs3733890 is a common single‑nucleotide polymorphism in the BHMT gene, part of the one‑carbon or methylation pathway. BHMT produces betaine‑homocysteine methyltransferase, an enzyme mainly active in liver and kidney that uses betaine as a methyl donor to convert homocysteine back to methionine, complementing folate‑dependent remethylation. Variants in BHMT have been studied for their effects on enzyme function and on downstream methylation chemistry. Research interest grew as scientists linked one‑carbon genetics to differences in homocysteine handling, methyl donor use, and interactions with dietary nutrients and other pathway genes.

Genetic variants can be associated with relative shifts in BHMT activity or regulation rather than simple 'high' or 'low' numeric results. Alleles associated with greater BHMT activity may correspond with increased betaine use for remethylation and altered patterns in methylation metabolites; in some settings this can appear alongside lower homocysteine or lower circulating betaine. Alleles associated with reduced BHMT activity may be linked with less remethylation via betaine, greater reliance on folate‑dependent pathways, and potential shifts in homocysteine and methylation markers. Any interpretation should be made in the context of the full Nutrient Zoomer panel, because diet, other genetic variants, and measured nutrient/metabolite levels shape the functional impact of BHMT variation.

Nutrient Zoomer includes rs3733890 to reveal inherited differences in one‑carbon metabolism and methyl donor use. This marker helps explain individual patterns in homocysteine handling, betaine interactions, and methylation demand. Combined with blood nutrient and metabolite measures, rs3733890 supports provider interpretation of biochemical patterns for personalized nutrition planning.