Introduction. Vitamin B12 is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement.Vitamin B12. A cooked steak presented atop asparagus and tomatoes. Foods from animals, but not plants, naturally have vitamin B12. These include fish, meat, .Vitamin B12 deficiency treatment options, diagnosis, and images at Epocrates Online, the leading provider of drug and disease decision support tools.Vitamin B6 is a water-soluble vitamin that is naturally present in many foods, added to Plasma PLP is the most common measure of vitamin B6 status. vitamin B6 (50 mg/day), vitamin B12 (1 mg/day), and folic acid (2.5 mg/day) reduced .The concentrations of RNA, DNA and protein are decreased in cells of Euglena gracilis var. bacillaris grown on suboptimum concentrations of vitamin.