B12, Requirement in Regard to Genetics

Kind of complex in structure...don't ya think?  

Kind of complex in structure...don't ya think?  

There are so many things to read about in the medical field that, to be honest, is overwhelming.  I try to limit my madness to subscribing to a few journals so I can review articles published each month.  As a Naturopathic Doctor and one who understands the essential component that food plays in our health and healing, I frequently read the American Journal of Clinical Nutrition.  

This month an article was published on genetic SNPs (Single Nucleotide Polymorphisms) related to B12 status and the risk of peripheral neuropathy.  Peripheral neuropathy is basically where the nerves in the peripheral nervous system (think anything outside the brain and spinal cord) are dying and can cause numbness and tingling.  About 33% of cases of peripheral neuropathy are induced by diabetes. But what about the rest?  

Vitamin B12 is a very finicky but interesting vitamin.  It's a group of molecules called cobalamins with 3 forms existing in the human body: Methyl-cobalamin, hydroxy-cobalamin, and adenosyl-cobalamin.  Another form of cobalamin you might commonly see is cyano-cobalamin which is cyanide bound to cobalamin.  This is said to be "GRAS" but you will not find me taking cyano-cobalamin.  

Once B12 is absorbed into the body, which becomes more challenging as we age, it is transported around in the blood through 2 main proteins, haptocorrin and transcobalamin.  Transcobalmin + B12 = holotranscobalamin and is the active b12 that can be transported into cells.  A few SNPs have been identified as having an effect on the shape of the transcobalamin protein which would then cause down-stream problems with getting B12 into cells like, oh I don't know... your brain!  

This cross-sectional study analyzed genetics from 171 men and women who were greater than 60 years old.  Odds of having peripheral neuropathy were 3.33x greater if the TCN2 677 GG types was present instead of the wild CC type.   These odds got even worse if you actually ate a high folate diet (like eating all that kale we should all be eating (serious, no sarcasm)).

Finally, I'd like to bring a balanced viewpoint regarding genes and how to act on the information they provide us.  Some studies, such as this one have shown no problems with TCN2 677 in younger healthy men.  I have also seen this SNP more commonly in my fibromyalgia patients.  If you have any neurological symptoms or diseases, which can be wide and varied from peripheral neuropathy to depression or even Alzheimer's, a therapeutic trial of intra-muscular B12 should be discussed.  If you have more questions, consider scheduling an appointment or consultation with me.