What Is Vitamin B6?

Jessica Clifton

by Jessica Clifton

29th July 2020

An essential nutrient that is found in many foods, vitamin B6 is crucial in the healthy functioning of our skin, blood, muscles, and central nervous system. Understanding what this vitamin is, therefore, can help you plan your diet more efficiently and allow you to live a healthier life. 

What Does Vitamin B6 Do? 

Vitamin B6 is a group of compounds that are chemically similar to each other, and vital to a range of biochemical reactions in the body. Like other essential nutrients from the vitamin B group, vitamin B6 is critically involved in cellular metabolism, specifically in the metabolism of proteins (amino acids), carbohydrates (glucose), and fats (lipids). 

Metabolism is divided into two categories: anabolism and catabolism. The latter is about breaking down biological molecules into constituent parts, while the former is about building complex biological molecules from constituent parts. 

Cellular metabolism uses a complex series of metabolic pathways that allow organisms to biosynthesise, reproduce and maintain their structures; and vitamin B6 is a crucial cofactor in many of these life-sustaining processes:

  • Amino Acids: Vitamin B6 regulates amino acids, the building blocks of proteins and neurotransmitters. Protein synthesis relies on this vitamin. Without it, complex proteins like hormones can become deficient, leading to illness. 

Amino acids are also involved in nearly every function of the body, from immune health to tissue growth. Therefore, a lack of vitamin B6 would have detrimental effects on nearly every aspect of our health. 

  • Glucose: Glycogenolysis is another important process in the body that breaks down glycogen into glucose in order to maintain blood sugar levels and provide energy. For glycogenolysis to occur, it needs glycogen phosphorylase, which vitamin B6 is a necessary coenzyme of. 
  • Lipids: Vitamin B6 is also a crucial cofactor in the biosynthesis of sphingolipids, and especially of ceramide. These are a group of lipids that are important for maintaining the function and structure of membranes and lipoproteins, as well as for preventing certain diseases.

What does vitamin B6 do

Although vitamin B6 deficiency is rare, people who are deficient in this vitamin may experience the following physical symptoms:

  • Seborrheic dermatitis
  • Glossitis, and cheilosis
  • Lethargy, or a lack of energy
  • A poor or weakened immune system

As a regulator of amino acids, vitamin B6 also has a role in the production of neurotransmitters. Without this vitamin, important neurotransmitters like serotonin, dopamine, norepinephrine and GABA (gamma aminobutyric acid) would be unable to biosynthesise. Therefore, a deficiency may also lead to neurological symptoms such as:

  • Seizures
  • Confusion
  • Depression
  • Peripheral neuropathy

While severe cases of deficiency are rare, marginal deficiency could be very common among pregnant and lactating women. This is because the foetus or baby will require additional nutrients derived from the mother’s diet. In these cases, taking supplements is sometimes necessary to avoid marginal deficiency.

It is clear to see that maintaining a healthy body and nervous system requires this essential nutrient. But what is the chemistry behind the life-sustaining vitamin B6?

The Chemistry of Vitamin B6

The chemical name for vitamin B6 is pyridoxine, while the chemical name for its active form is pyridoxal phosphate. Its active form can also be expressed by the IUPAC ID: (4-formyl-5-hydroxy-6-methylpyridin-3-yl)methyl phosphate. Other names for vitamin B6 include:

  • PAL-P, or PLP
  • Pyridoxal 5-phosphate
  • Vitamin B6 phosphate

According to the International Union of Biochemistry and Molecular Biology (IUBMB), there are more than 140 biochemical reactions that are dependent on vitamin B6 as a coenzyme. One of the reasons pyridoxal phosphate is highly versatile like this is because of its ability to create covalent bonds for the substrate. It then serves as a catalyst that attracts electrons. This stabilises the various kinds of carbanionic reaction intermediaries.

Since vitamin B6 is actually a group of three chemically similar compounds, there are three vitamin B6 chemical formulas:

  • Pyridoxine: 

Containing a methyl hydroxyl group (-CH3OH), its complete molecular formula is C8H11NO3

  • Pyridoxal:

This has an aldehyde group (-CHO) and so the complete molecular formula is C8H9NO3

  • Pyridoxamine:

This compound has an aminomethyl group (-CH3NH2), and the chemical formula is C8H12N2O2

All three of these vitamin B6 forms can be made active through something called the phosphorylation process. When phosphorylated, these forms can be interconverted into the cofactor form, i.e. the active form known as pyridoxal phosphate, or PLP. During this process, the hydroxyl group is replaced by a phosphate group, and this reaction is made possible by the enzyme reaction of riboflavin cofactor.

Structurally, the phosphate group of this vitamin’s active form has a phosphorus with two oxygen atoms attached to it. One oxygen is single bonded, while the other oxygen is double bonded. Two hydroxyl groups are also attached to the phosphorus. The cyclic or aromatic groups are very similar among the three forms of vitamin B6, as well as its active form.

Is Vitamin B6 Water Soluble?

All essential nutrients from the vitamin B group are soluble in water, including vitamin B6:

  • Unlike fat-soluble vitamins, like vitamin E and vitamin D, B6 does not accumulate in cells
  • Since it dissolves in water, excess amounts of this vitamin are removed from the body via urine
  • This makes it very difficult for vitamin B6 to reach toxic levels in the body through diet alone

Because vitamin B6 is not stored or created naturally by the body, and because it is readily excreted in urine, it means that we must constantly replenish our stores of this nutrient by consuming food that is rich with it. Luckily for us, these types of foods are very common. 

What Foods Contain Vitamin B6?

Foods that contain vitamin B6

Foods that contain vitamin B6

B complex vitamins, like vitamin B6, are abundant in many types of foods, making it easy to ensure that this essential nutrient is in your diet. Here are some foods that are rich in vitamin B6:

  • Pork
  • Nuts
  • Poultry
  • Yeast extract
  • Whole grains
  • Fish, particularly:
    • Trout and salmon
    • Herring and halibut
    • Tuna, especially yellowfin
  • A few fruits and vegetables, including:
    • Beans
    • Raisins
    • Bananas
    • Cauliflowers

An adult male aged 19 to 64 needs approximately 1.4 mg of vitamin B6 per day, and it’s 1.2 mg per day for women. Given that this nutrient is essential to our health, it is a relief to know that the minimum amount of vitamin B6 required by our bodies is easily derived from common foods. 

In most cases, there is actually no need to take supplements for vitamin B6. In fact, consuming too much of this vitamin can be just as detrimental to your health as not consuming enough. If you are taking high-dose supplements of this vitamin at more than 1,000 mg a day, toxicity levels can be reached. This is because excess amounts won’t be able to be removed through urine.  

Some of the common symptoms of toxicity that can be caused by vitamin B6 are:

  • Gastrointestinal problems
  • Neuropathy in feet and hands
  • Inability to sense pain or temperatures
  • Loss of body control and movements, or ataxia

As long as you are regularly consuming the right kinds of foods, and not taking too many supplements, it  is very unlikely that you will experience any symptoms of deficiency or toxicity from this vitamin. But there are some at-risk groups who may be more deficient in vitamin B6 than others:

  • People with kidney failure
  • People with liver disease
  • People who are alcoholics

What is Pyridoxine?

Pyridoxine is one of the major forms of vitamin B6. Chemically speaking, it is distinct from other forms of vitamin B6 because it has a methyl hydroxyl group (-CH3OH). In terms of molecular formula, it can be represented as C8H11NO3

Pyridoxine molecular formula

Pyridoxine is usually sold as a food supplement and used in the treatment of certain medical conditions, including:

  • Epilepsy
  • Sideroblastic anaemia
  • Some metabolic disorders
  • Problems from isoniazid
  • Certain types of mushroom poisoning

The treatment of a rare type of epilepsy, known as pyridoxine-dependent epilepsy, requires regular supplementation of vitamin B6. This type of epilepsy does not respond well to anti-seizure medicines. It can also be taken in combination with doxylamine to treat morning sickness among pregnant women.


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