Nutritional deficiency diseases are illnesses caused by a lack of essential vitamins and minerals in the diet. Two examples of these diseases are pellagra and SCURVY. Pellagra is a disease caused by a deficiency of niacin, which is found in certain foods such as meat, fish, and eggs. Symptoms of pellagra include skin rashes, diarrhea, and mental confusion. SCURVY is a disease caused by a deficiency of vitamin C, which is found in citrus fruits and other vegetables. Symptoms of SCURVY include bleeding gums, joint pain, and fatigue. Both pellagra and SCURVY can be prevented by eating a balanced diet that includes all the essential vitamins and minerals.