Vitamin B. Polarised light micrograph of crystals of niacinamide (also known as nicotinamide). This is the amide of nicotinic acid, the two compounds being interchangeable. They are both B vitamins, and are equally active. Niacinamide is a component of two vital coenzymes, NAD (nicotinamide adenine dinucleotide) and its phosphate NADP, which are responsible for electron transport in cellular respiration. A deficiency of these and other B vitamins may lead to pellagra, symptomised by severe dermatitis, diarrhoea and depression. Sources of niacinamide include vegetables, lean meat, milk and some cereals (but not maize). Magnification x16 at 5x7cm size. Magnification x8 at 35mm size.