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 5′-phosphate (PLP) is the active form of vitamin B6. Pyridoxine hydrochloride is the form of B6 that is most commonly used as a dietary supplement due to its chemical stability.
Chemically, B6 vitamers are derivatives of 2-methyl-3-hydroxy-5-hydroxymethyl-pyridine where a C4 position can substitute by a hydroxymethyl group in pyridoxine, an aminomethyl group in pyridoxamine, and an aldehyde group in pyridoxal.
The alcohol group present in the 5′ positions can be esterified to phosphate to form pyridoxine 5′-phosphate (PNP), pyridoxamine 5′-phosphate (PMP), and pyridoxal 5′-phosphate (PLP).
The phosphate form is inconvertible in our bodies. Vitamin B6 is beneficial for the development of the nervous system and the metabolism of protein, carbohydrates, and fats. Therefore, B6 uses mainly for turning food into energy and helps to create neurotransmitters.
Sources of vitamin B6
The main sources of vitamin B6 for humans are the diet. It can be found in a variety of animal and plant foods.
- Beef liver
- Yellowfin tuna
- Fortified cereals
- Cottage cheese
- Roasted chicken breast
Some vegetables and fruits, dark leafy greens, bananas, papayas, oranges, and cantaloupe contain principally pyridoxine and its phosphate and glucoside forms of B6. In meat and fish, B6 is mainly present as PLP and PMP.
The average vitamin B6 content of human milk is low in early childbirth. High-performance liquid chromatography analysis indicates that B6 in human milk contains pyridoxal, pyridoxal-5-phosphate, pyridoxamine, and pyridoxamine-5′-phosphate. The supplementation of mothers with 2.5 or 15 mg of pyridoxine gives similar distribution patterns for the vitamers in milk.
Vitamin B6 recommended daily intake
Like other B vitamins, our body does not store B6 and releases any excess in urine. Therefore, people need to get enough vitamin B6 reached foods or supplements every day.
The daily requirement for B6 depends on several factors because B6 controls various biological reactions of a person. The recommended daily dietary allowances (RDA) for vitamin B6 are,
|0–6 months||0.1 mg||0.1 mg|
|7–12 months||0.3 mg||0.3 mg|
|1–3 years||0.5 mg||0.5 mg|
|4–8 years||0.6 mg||0.6 mg|
|9–13 years||1.0 mg||1.0 mg|
|14–18 years||1.3 mg||1.2 mg|
|19–50 years||1.3 mg||1.3 mg|
|51+ years||1.7 mg||1.5 mg|
|During pregnancy||1.9 mg|
|During breastfeeding||2.0 mg|
Vitamin B6 supplement
Vitamin B6 supplements are available in capsule or tablet form to treat B6 deficiency. Pyridoxine hydrochloride is available as a licensed drug or supplement for oral administration in most Western countries. It is converted to pyridoxamine 5′-phosphate (PMP) by the enzyme pyridoxal kinase.
The metabolically active form of B6 (pyridoxal 5′-phosphate) may be obtained by the enzymes pyridoxamine-phosphate transaminase or pyridoxine 5′-phosphate oxidase. The activity of the enzyme pyridoxine 5′-phosphate oxidase is dependent on flavin mononucleotide (FMN). FMN is a cofactor produced from riboflavin (vitamin B2).
Most people of all ages in developed counties consume sufficient B6 and do not require supplements. Those who are more likely to have low levels of B6 and required supplementation may include:
- people who drink excess alcohol
- people with obesity
- during pregnancy or breastfeeding periods
Functions of vitamin B6
Functions in metabolism
The metabolism of protein, carbohydrates, and fats is the main function of vitamin B6.
- In protein metabolism, B6 helps to regulate the balance of amino acids in the body.
- PLP undergoes a condensation reaction with the amino group of amino acids to produce a Schiff base. It forms the basis of most of the enzyme-catalyzed reactions for which PLP is required.
- Pyridoxal 5′-phosphate is a coenzyme that is involved in glycogenolysis of the body. It enables the breakdown of glycogen into glucose for energy production. Glycogenolysis is primarily found in muscle, liver, and brain.
- PLP is one of the B6 vitamers which are required for the normal metabolism of fats and essential fatty acids. It is an essential component of enzymes that facilitate the biosynthesis of sphingolipids. For example, the synthesis of ceramide requires PLP.
- Selenomethionine is the primary dietary supplement for selenium. The cofactor PLP is used to activate enzymes that allow selenium to be used from the dietary form.
Functions in hemoglobin synthesis
The biosynthesis of hemoglobin depends on the activity of the enzyme aminolevulinic acid synthase. PLP serves as a coenzyme for the enzyme aminolevulinic acid synthase.
Vitamin B6 (Pyridoxal 5′-phosphate) is a coenzyme that helps in the biosynthesis of five important neurotransmitters. These are serotonin, dopamine, epinephrine, norepinephrine, and gamma-aminobutyric acid. These are important chemical messengers that help regulate energy in our brains.
A recent study suggests that vitamin B6 has modulated gene expression not only for steroid hormone-responsive or PLP-dependent enzymes but also for steroid- and PLP-unrelated proteins such as serum albumin. PLP has been implicated in increasing or decreasing the expression of certain types of genes.
Albumin gene expression by B6 goes through a novel mechanism. It involves the inactivation of tissue-specific transcription factors, such as HNF-1 or C/EBP.
Vitamin B6 in fertility
- B6 can raise the levels of progesterone hormone that makes the body ready for pregnancy.
- Vitamin B6 helps in the production of cervical mucus that transports the sperm to reach the egg.
- The menstrual cycle for women consists of two phases – the follicular phase and the luteal phase. The luteal phase of the menstrual cycle is strengthened by B6. It makes the uterus more receptive and increases the chance of pregnancy.
- It can increase or restore libido. Hence B6 may increase the sexuality of men and women.
Uses of vitamin B6
Plants synthesize pyridoxine to protect from the ultraviolet-B radiation of sunlight. Pyridoxine also participates in the synthesis of chlorophyll.
Animals cannot synthesize any of the various forms of vitamin B6. Therefore, they must obtain B6 via diet, either of plants or other animals.
- Vitamin B6 plays an important role in protein, carbohydrates, and fats metabolism.
- It also participates in the production of neurotransmitters, hemoglobin, and the formation of nicotinic acid. Therefore, vitamin B6 is vital for maintaining a healthy nervous system, skin, muscles, and blood.
- Vitamin B6 supplementation may help in mild symptoms of morning sickness, nausea, and vomiting during pregnancy.
- B6 may help to protect us from the harmful effects of air pollution by reducing the impact of pollution on the epigenome.
- The forms of vitamin B6, pure crystalline pyridoxine powder, or pyridoxine hydrochloride supplements are used in amino acid metabolism and maintain healthy or oily skin.
Benefits of vitamin B6
B6 is a vitamin that is beneficial for our central nervous system and the metabolism of the human body. PLP is the only B6 vitamer that assists more than 100 enzymes in performing various biological functions.
- It benefits brain development during pregnancy and infancy.
- B6 creates neurotransmitters, including serotonin and dopamine.
- It creates hemoglobin which is the part of red blood cells that carries oxygen in human bodies.
- It helps to regulate the balance of amino acids in our body.
- B6 is also closely involved in hormone synthesis.
Vitamin B6 and weight loss
Vitamin B6 plays a crucial role in metabolizing protein, fats, and carbohydrates in our bodies. In presence of B6, our metabolism speeds up and allows us to burn calories and lose weight quicker.
Vitamin B6 deficiency
Deficiencies of vitamin B6 are uncommon in the United States and other developed counties. The deficiency of B6 may happen if a person has poor intestinal absorption or takes some medicines. The deficiencies of B6 may cause low levels of other B vitamins, such as vitamin B12 and folic acid (folate).
The main signs and symptoms of a B6 deficiency may include:
- Tingling, numbness, and pain in the hands and feet (peripheral neuropathy)
- Weakened immune system
- Seborrheic dermatitis
- Inflammation of the tongue, or glossitis
- Inflammation and cracking of the lips
The vitamin B6 level is decreased for women with type 1 diabetes and patients with systemic inflammation, liver disease, rheumatoid arthritis, and infected with HIV.
Diagnosis of B6 deficiency is usually clinical and measurement of serum pyridoxal phosphate is most common to measure B6 deficiency. There is no single accepted laboratory test to measure the B6 level.
Other useful methods to measure vitamin B6 levels may include UV spectrometry, spectrofluorimetry, mass spectrometry, thin-layer chromatography, high-performance liquid chromatography, electrochemical, and enzymatic methods.