B complex vitamins, a large group of water-soluble nutrients that includes thiamine (vitamin B1), cyanocobalamin (vitamin B12), niacin (vitamin B3), pyridoxine (vitamin B6), riboflavin (vitamin B2), biotin, folic acid, and pantothenic acid. The B complex vitamins are essential, for example, for the conversion of simple carbohydrates like glucose and the carbon skeletons of amino acids into energy, and for the metabolism of fats and proteins. Good sources include brewer’s yeast, liver, whole grain cereals, nuts, eggs, meats, fish, and vegetables. Because some B complex vitamins are produced by intestinal bacteria, taking antibiotics may destroy these bacteria. Symptoms of vitamin B deficiency include nervousness, depression, insomnia, neuritis, anemia, alopecia, acne or other skin disorders, and hypercholesterolemia.
