What are vitamins?

Vitamins are organic compounds or essential micronutrients that are found in various types of foods and are necessary for the growth and good health of animals including humans. Vitamins are accessory dietary factors and are only necessary for very small amounts.

Vitamins (A, D, E, B vitamins and vitamin C) Sources with Definition, Classification and Examples

In addition to oxygen, water, proteins, fats, carbohydrate, and certain inorganic salts, vitamins are also necessary for our life. It cannot be produced by our body. Hence, we need to intake foods or supplements that contain various vitamins. However, vitamin D may be supplied in food or may be produced in the skin by irradiation of ultraviolet-visible light from the sun.

Most vitamins do not contain a single molecule but contain a group of related molecules. Therefore, they are called vitamers. For example, eight vitamers are found in vitamin E, four tocopherols, and four tocotrienols. In B6, six related molecules are found.


The vitamins have been arbitrarily classified into two groups, fat-soluble or water-soluble. Four are fat-soluble (A, D, E, and K) and nine are water-soluble (8 B vitamins and vitamin C) among 13 vitamins found in humans.

Fat-soluble vitamins

Fat-soluble vitamin is an essential micronutrient soluble in fat and found in many plant and animal foods and in dietary supplements. They are absorbed along with fats in our diet and are stored in our body’s fatty tissue and in the liver. These may include,

  1. Vitamin A (Retinol)
  2. D (Cholecalciferol, Ergocalciferol)
  3. E (Tocopherols, Tocotrienols)
  4. K (Phylloquinone, Menaquinones)

Water soluble vitamin

The nine water-soluble vitamins are found in the human diet. These may include,

  1. Vitamin B1 (thiamine)
  2. Vitamin B2 (riboflavin)
  3. Vitamin B3 (niacin)
  4. Vitamin B5 (pantothenic acid)
  5. Vitamin B6 (pyridoxine, pyridoxamine, pyridoxal)
  6. Vitamin B7 (biotin)
  7. Vitamin B9 (folates, folic acid)
  8. Vitamin B12 (cyanocobalamin, hydroxocobalamin, methylcobalamin, adenosylcobalamin)
  9. Vitamin C (ascorbic acid)

Uses, sources, biological functions, supplements, side effects, and many more about various vitamins are given below the individual topics in this category,

Vitamin E uses, benefits for skin, hair, vision, menopause, immune system with natural dietary supplements and deficiency

Vitamin E

What is Vitamin E? Vitamin E is a fat-soluble vitamin and a powerful antioxidant that is beneficial for immune health and cellular signaling in your...
Vitamin B5 (pantothenic acid) benefits to skin, hair and nerve with B5-reached foods and supplements, deficiency effects on health

Vitamin B5

Vitamin B5 (Pantothenic Acid) Vitamin B5 (Pantothenic Acid) is a water-soluble B vitamin present naturally in various foods and available as a supplement. In general,...
Vitamin K uses and benefits of vitamin K1 (phylloquinone) and vitamin K2 (menaquinones) with sources and deficiency symptoms

Vitamin K

What is Vitamin K? Vitamin K is a fat-soluble vitamin that helps to make various proteins that are needed for blood clotting and the binding...
Vitamin B7 (Biotin) or vitamin H sources foods rich in biotin with uses, supplement, benefits, and deficiency

Vitamin B7

Vitamin B7 (Biotin) Vitamin B7 (Biotin) or Vitamin H is one of the B vitamins that is found in various natural food sources and supplements....
Niacinamide or Nicotinamide (NAM) and Nicotinic acid or Niacin (vitamin B3) supplements and serum for Skin with Uses, Benifits


What is Niacinamide? Niacinamide or Nicotinamide (NAM) is a water-soluble form of vitamin B3 or niacin. The crystalline powder and niacinamide serum are used in...
Vitamin B3 sources and supplements of Niacin, Nicotinamide, and Nicotinamide riboside with benefits, uses and deficiency

Vitamin B3

Vitamin B3 (Niacin) Vitamin B3 (Niacin) is a water-soluble B vitamin found naturally in some foods and sold as a supplement. Nicotinamide (niacinamide), niacin (nicotinic...
Vitamin C (ascorbic acid) sources in dietary fruits, citrus fruits and vegetables with supplement, uses, deficiency

Vitamin C

What is Vitamin C? Vitamin C (ascorbic acid and ascorbate) is a water-soluble vitamin found in many fruits mainly citrus fruit and vegetable sources. Many...
Vitamin A (retinol, retinal, retinoic acid and beta carotene) with uses, benefits, sources, supplements, deficiency of Vitamin A

Vitamin A

What is vitamin A? Vitamin A referred to a group of organic compounds that includes retinol, retinal, retinoic acid, and several provitamins A carotenoids like...
Pyridoxal 5'-phosphate Active form of Vitamin B6 with Uses, Supplements, Functions and Benefit

Vitamin B6

What is vitamin B6? Vitamin B6 is a water-soluble vitamin or essential nutrient found naturally in various foods and added to foods and supplements. Pyridoxal...
Vitamin B12 also known as cobalamin structure with deficiency, natural food sources, functions

Vitamin B12

What is vitamin B12? Vitamin B12, also known as cobalamin, is a water soluble vitamin containing cobalt in its structure. Like folic acid, vitamin B12 deficiency...