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Each vitamin is typically used in multiple reactions, and, therefore, most have multiple functions.
| Vitamin generic descriptor name | Vitamer chemical name(s) | Recommended dietary allowances (male, age 19–70) | Deficiency disease | Food sources |
| Vitamin A | Retinol, retinal, and four carotenoids including beta carotene | 900 µg | Night-blindness, keratosis | Orange, ripe yellow fruits, leafy vegetables, carrots, pumpkin, squash, spinach, liver, soy milk, milk |
| Vitamin B1 | Thiamine | 1.2 mg | Beriberi, Wernicke-Korsakoff syndrome | Pork, oatmeal, brown rice, vegetables, potatoes, liver, eggs |
| Vitamin B2 | Riboflavin | 1.3 mg | Ariboflavinosis | Dairy products, bananas, popcorn, green beans, asparagus |
| Vitamin B3 | Niacin, niacinamide | 16.0 mg | Pellagra | Meat, fish, eggs, many vegetables, mushrooms, tree nuts |
| Vitamin B5 | Pantothenic acid | 5.0 mg | Paresthesia | Meat, broccoli, avocados |
| Vitamin B6 | Pyridoxine, pyridoxamine, pyridoxal | 1.3–1.7 mg | Anemia peripheral neuropathy. | Meat, vegetables, tree nuts, bananas |
| Vitamin B7 | Biotin | 30.0 µg | Dermatitis, enteritis | Raw egg yolk, liver, peanuts, certain vegetables |
| Vitamin B9 | Folic acid, folinic acid | 400 µg | Megaloblastic anemia and Deficiency during pregnancy is associated with birth defects, such as neural tube defects | Leafy vegetables, pasta, bread, cereal, liver |
| Vitamin B12 | Cyanocobalamin, hydroxycobalamin, methylcobalamin | 2.4 µg | Megaloblastic anemia | Meat and other animal products |
| Vitamin C | Ascorbic acid | 90.0 mg | Scurvy | Many fruits and vegetables, liver |
| Vitamin D | Cholecalciferol, Ergocalciferol | 10 µg | Rickets and Osteomalacia | Fish, eggs, liver, mushrooms |
| Vitamin E | Tocopherols, tocotrienols | 15.0 mg | Deficiency is very rare; mild hemolytic anemia in newborn infants. | Many fruits and vegetables, nuts and seeds |
| Vitamin K | phylloquinone, menaquinones | 120 µg | Bleeding diathesis | Leafy green vegetables such as spinach, egg yolks, liver |
Vitamins are classified as either water-soluble or fat-soluble. In humans there are 13 vitamins: 4 fat-soluble (A, D, E, and K) and 9 water-soluble (8 B vitamins and vitamin C). Water-soluble vitamins dissolve easily in water and, in general, are readily excreted from the body, to the degree that urinary output is a strong predictor of vitamin consumption. Because they are not as readily stored, more consistent intake is important. Many types of water-soluble vitamins are synthesized by bacteria. Fat-soluble vitamins are absorbed through the intestinal tract with the help of lipids (fats). Because they are more likely to accumulate in the body, they are more likely to lead to hypervitaminosis than are water-soluble vitamins. Fat-soluble vitamin regulation is of particular significance in cystic fibrosis.
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