essential vitamins

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There are 13 essential vitamins necessary for the normal health and growth of the human body. Given that vitamins cannot usually be synthesized by the body in sufficient amounts, they must be obtained from the diet or from some synthetic source. They are traditionally separated into two groups: water-soluble vitamins and fat-soluble vitamins. The following table lists the common and chemical names of the essential vitamins, along with their main biological functions and deficiency symptoms.

Water-soluble vitamins
vitamin	alternative names/forms	biological function	symptoms of deficiency
thiamin	vitamin B₁	component of a coenzyme in carbohydrate metabolism; supports normal nerve function	impairment of the nerves and heart muscle wasting
riboflavin	vitamin B₂	component of coenzymes required for energy production and lipid, vitamin, mineral, and drug metabolism; antioxidant	inflammation of the skin, tongue, and lips; ocular disturbances; nervous symptoms
niacin	nicotinic acid, nicotinamide	component of coenzymes used broadly in cellular metabolism, oxidation of fuel molecules, and fatty acid and steroid synthesis	skin lesions, gastrointestinal disturbances, nervous symptoms
vitamin B₆	pyridoxine, pyridoxal, pyridoxamine	component of coenzymes in metabolism of amino acids and other nitrogen-containing compounds; synthesis of hemoglobin, neurotransmitters; regulation of blood glucose levels	dermatitis, mental depression, confusion, convulsions, anemia
folic acid	folate, folacin, pteroylglutamic acid	component of coenzymes in DNA synthesis, metabolism of amino acids; required for cell division, maturation of red blood cells	impaired formation of red blood cells, weakness, irritability, headache, palpitations, inflammation of mouth, neural tube defects in fetus
vitamin B₁₂	cobalamin, cyanocobalamin	cofactor for enzymes in metabolism of amino acids (including folic acid) and fatty acids; required for new cell synthesis, normal blood formation, and neurological function	smoothness of the tongue, gastrointestinal disturbances, nervous symptoms
pantothenic acid		as component of coenzyme A, essential for metabolism of carbohydrate, protein, and fat; cofactor for elongation of fatty acids	weakness, gastrointestinal disturbances, nervous symptoms, fatigue, sleep disturbances, restlessness, nausea
biotin		cofactor in carbohydrate, fatty acid, and amino acid metabolism	dermatitis, hair loss, conjunctivitis, neurological symptoms
vitamin C	ascorbic acid	antioxidant; synthesis of collagen, carnitine, amino acids, and hormones; immune function; enhances absorption of nonheme iron (from plant foods)	swollen and bleeding gums, soreness and stiffness of the joints and lower extremities, bleeding under the skin and in deep tissues, slow wound healing, anemia

Fat-soluble vitamins
vitamin	alternative names/forms	biological function	symptoms of deficiency
vitamin A	retinol, retinal, retinoic acid, beta-carotene (plant version)	normal vision, integrity of epithelial cells (mucous membranes and skin), reproduction, embryonic development, growth, immune response	ocular disturbances leading to blindness, growth retardation, dry skin, diarrhea, vulnerability to infection (see vitamin A deficiency)
vitamin D	calciferol, calatriol (1,25-dihydroxy vitamin D₁ or vitamin D hormone), cholecalciferol (D₃; plant version), ergocalciferol (D₂; animal version)	maintenance of blood calcium and phosphorus levels, proper mineralization of bones	defective bone growth in children, soft bones in adults deficiency
vitamin E	alpha-tocopherol, tocopherol, tocotrienol	antioxidant; interruption of free radical chain reactions; protection of polyunsaturated fatty acids, cell membranes	peripheral neuropathy, breakdown of red blood cells
vitamin K	phylloquinone, menaquinone, menadione, naphthoquinone	synthesis of proteins involved in blood coagulation and bone metabolism	impaired clotting of the blood and internal bleeding

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Melissa Petruzzello.