This observation provides a plausible explanation for some inconsistent findings regarding associations of L-carnitine and choline with the risk of T2DM, i.e., the effects of the supplement of L-carnitine and choline being particularly large among CDKAL1 rs7747752 CC/CG genotype carriers who also had a low serum level of L-carnitine or choline. The gene discussed is CDKAL1; the disease is type 2 diabetes mellitus.