Vitamin B12. Polarised light micrograph of crystals of Vitamin B12 (cyanocobalamin). This is one of the water- soluble B-complex vitamins, and is necessary for the synthesis of nucleic acids and the maintenance of myelin in the nervous system. Vitamin B12 deficiency affects almost all body tissues. The most serious effects of this are pernicious anaemia and a degeneration of the nervous system. Vitamin B12 is contained only in foods of animal origin, especially liver, fish and eggs. Recommended adult daily intake is 3-4 microgrammes. Magnification x16 at 5x7cm size. Magnification x8 at 35mm size.