I used to joke that the last thing I needed was to "B" more complex. Wrong again...
B vitamins are worthy of a long post; however, my intent is to highlight one area that recently caught my attention. Deficiencies of vitamins B6 and B12 and folate can prevent homocysteine from converting rapidly enough.
Homocysteine is an amino acid that is produced in the body in the course of methionine metabolism. Homocysteine has been the focus of increasing attention in recent years because high levels are associated with an increased risk of cardiovascular disease. Further, it is known that homocysteine has a toxic effect on cells lining the arteries, makes the blood more prone to clotting, and promotes the oxidation of low-density lipoproteins (LDL -- "bad cholesterol"), which makes it more likely that cholesterol will be deposited as plaque in blood vessels.
If high levels of homocysteine accumulate in the body, it can damage cell membranes and blood vessels and potentially increase the risk of cardiovascular disease.
Vitamin B6 and B12 and folate work together to facilitate the breakdown of homocysteine and thus help protect against heart disease.
Balch, Phyllis. "Prescription for Nutritional Healing." Amino Acids. Homocysteine, p. 49.