Vitamins and Amino Acids Explained

Lucy Bell-Young

by Lucy Bell-Young

24th November 2021

Both vitamins and amino acids are important nutrients in the human body, performing various crucial functions.

Vitamins are considered micronutrients and mainly function as cofactors and coenzymes in different metabolic processes, such as regulating protein synthesis. Meanwhile, amino acids are the fundamental building blocks of proteins. For instance, vitamin B12 or cobalamin has an important role in protein catabolism and the synthesis of red blood cells.

Amino acids are technically macronutrients, because they’re components of proteins and are needed in relatively large amounts compared to vitamins. Nonetheless, many of the functions of proteins would not be possible without vitamins, including protein synthesis.

What Are Vitamins?

Vitamins are considered micronutrients because our bodies only need them in small quantities. Compared to macronutrients like proteins, carbohydrates, and lipids, vitamins don’t form structures or directly participate in biochemical reactions. They mainly assist other organic molecules, as well as inorganic molecules to efficiently react to fulfill specific functions.

For example, vitamin B5, otherwise known as pantothenic acid, has an important role in the Krebs cycle (or aerobic cellular respiration) as a coenzyme. This vitamin functions as coenzyme A, which carries the carbon-based molecules in a cell.

Vitamins are classified as either fat-soluble or water-soluble vitamins. Fat-soluble vitamins build up in body tissue and may cause problems if over-consumed. Water-soluble vitamins rarely cause toxicity due to overdose because they’re easily metabolised and excreted by the body.

The fat-soluble vitamins include:

  • Vitamin A: Primarily, this has an important role in healthy vision. The active form, known as retinoids, comes from animals, while the inactive form, beta carotene, comes from plants like carrots.
  • Vitamin D: Vitamin D is crucial to bone health. It can be produced by the skin when it’s exposed to UV rays from the sun. It can also be derived from food.
  • Vitamin E: This has several forms but the only useful form is alpha-tocopherol, which is an important antioxidant.
  • Vitamin K: Vitamin K has two forms. The main form is phylloquinone, which is found in green leafy vegetables. The other form is menaquinones, which are found in some animal products and in fermented foods. It’s very important in the synthesis of various types of proteins.
Chemical formulas of fat soluble vitamins

The water-soluble vitamins include: 

  • Vitamin C: This is considered as the master antioxidant. It helps to boost the immune system, aiding normal growth, and repairing tissues. It helps counter ageing by neutralising free radicals in the body.
  • Thiamine (B1): Thiamine has an important role in the metabolism of glucose. It helps in the process of breaking down glucose to produce ATP during aerobic cellular respiration. DNA and RNA synthesis are also dependent on thiamine.
  • Riboflavin (B2): This has a role in the metabolism of macronutrients. It’s a coenzyme that acts as an electron carrier. 
  • Niacin (B3): Similar to vitamin B2, niacin has a role in breaking down carbohydrates, lipids, and proteins. It helps to boost good cholesterol, and can be synthesised by the human body from the amino acid tryptophan.
  • Pantothenic acid (B5): The main role of this vitamin is the synthesis of coenzyme A (CoA) and acyl carrier protein. 
  • Pyridoxine (B6): This is another vitamin B that plays an important role in the synthesis of protein from amino acids. It also has a catabolic role in terms of breaking down glycogen into glucose.
  • Biotin (B7): This is important in the Krebs cycle and as well as in metabolising lipids. It also has a role in synthesising non-essential amino acids.
  • Folate (folic acid): Folate is essential for the development of the brain of a foetus, helping support the healthy division of cells. As a coenzyme, it aids in the synthesis of methionine (an essential amino acid). It also helps in synthesising and repairing genetic materials (DNA and RNA).
  • Cobalamin (B12): This is the only vitamin that has a metal ion component, which is cobalt. It’s also important to the synthesis of red blood cells.
Two litsts of water soluble and fat soluble vitamins

Are Vitamins Made of Amino Acids?

No, vitamins are not made of amino acids. Otherwise, it would be a protein, which is a macronutrient. However, some vitamins are naturally synthesised from amino acids.

For example, vitamin B3 or niacin can be synthesised by the human body from the amino acid tryptophan. The process requires enzymes that are dependent on vitamin B2, vitamin B6, and iron.

What Vitamin is Involved in Amino Acid Metabolism?

Amino acid metabolism is either anabolic or catabolic. This means it either builds new molecules like proteins or breaks molecules down.

Although many vitamins, particularly the vitamin B group, are involved in the metabolism of protein, very few vitamins are directly involved in the metabolism of amino acids. Vitamin B6 is notable because it has the role of carrying amino acids into the cells. It’s thus involved in the synthesis of amino acids with the help of enzymes.

Do All Vitamins Contain Amino Acids?

Protein synthesis is an anabolic process that involves the building of protein molecules from simpler fundamental building blocks: the amino acids.

Although some water-soluble vitamins like vitamin B1, B3, and folic acid have an amine functional group in them, vitamins do not contain amino acids. As a side note, none of the fat-soluble vitamins contain an amine functional group (-NH2).

An amino acid has the following general structure:

Amino acid structure

No vitamin satisfies this general chemical molecular structure of amino acids. Although some vitamins, like vitamin B12, are more complex than some amino acids, the general chemical structure and properties of an amino acid is not satisfied by any vitamin. For instance, vitamins cannot link together to form a protein.


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