Vitamin B3 deficiency. Cracked and inflamed skin of a man, a symptom that his diet is deficient in vitamin B3, a disorder that is known as pellagra. Other pellagra symptoms are an upset digestive system, diarrhoea and depression. Vitamin B3 exists in two forms: niacinamide and niacin. One of the complex of B vitamins, it takes part in many metabolic reactions and, like other vitamins, is needed only in small amounts, but is an essential part of a healthy diet. Good sources of vitamin B3 are liver meat, groundnuts and seeds from the sunflower plant. Photographed in Africa.