Scientists have identified the first genetic variants that contribute to variation in levels of vitamin B12, according to a study published online this week in Nature Genetics.
Vitamin B12 is found in meat and milk products, and is necessary for the formation of red blood cells. Deficiency of vitamin B12, whether due to direct dietary deficiency or inadequate absorption in the intestine, is associated with anaemia, cardiovascular disease, cancer, and neurodegenerative disorders. David Hunter and colleagues carried out a genome-wide association study in search of common genetic variation that might influence plasma levels of B12. They found three highly correlated single-nucleotide polymorphisms (SNPs) in the gene FUT2 to be associated with B12 levels.
FUT2 encodes, an enzyme that links certain types of sugars and that, among other things, regulates the secretion of the factors that constitute an individual’s blood type. One of the B12-associated SNPs renders FUT2 nonfunctional, and has been referred to as the ‘nonsecretor’ variant because it prevents secretion of the blood-type factors. The ‘secretor’ version of FUT2 has been associated with infection by the bacterium Helicobacter pylori, which can cause gastritis. The authors suggest that genetic variation in FUT2 may influence B12 levels via H. pylori, which others have shown to be associated with B12 malabsorption.