Vitamin B6

Introduction image

Vitamin B6 is a water-soluble vitamin, which belongs to the family of the vitamin B complex. It is named as “Vitamin B6” because it comprises six vitamers, namely pyridoxine, alcohol, pyridoxal, an aldehyde, pyridoxamine and 2, 5’-phosphate esters.

Naturally, it is present as a glycosylated form in fruits and vegetables or exhibit reduced bioavailability. Pyridoxine should be supplemented in our regular diet as it is essential for our brain health, immune function and various metabolic pathways.

Content: Vitamin B6

  1. Definition
  2. Food Sources
  3. Dosage
  4. Absorption
  5. Dietary Supplement
  6. Deficiency
  7. Functions
  8. Uses

Definition of Vitamin B6

Vitamin B6 can define as the water-soluble vitamin that is found naturally in a wide range of food and artificially it can be supplemented in the form of an oral capsule, tablet or tonic. Pyridoxal 5’ phosphate and pyridoxamine 5’ phosphate are the two coenzymes of vitamin B6 that actively participates in the metabolism of biomolecules, production of haemoglobin, functioning of the nervous system and immune system etc.

Food Sources

As vitamin B6 is water-soluble, it cannot be stored in our body and excreted out in the form of urine. So, it becomes necessary to intake food rich in Pyridoxine. The most common food sources of vitamin B6 complex are:
Food sources of vitamin B6

  • Beef liver
  • Tuna, Salmon
  • Fortified cereals
  • Chickpeas
  • Starchy vegetables
  • Fruits other than citrus types.

Dosage

Generally, DRI is a term used as reference value used in planning and managing nutrients requirement of healthy people, and it stands for Dietary Reference Intakes. DRI is developed by the Food and Nutrition Board situated in Washington DC. These values vary by gender and age group and include the following things:

Recommended Dietary Allowance (RDA): Daily average intake requirements of the nutrients is decided to meet the nutritional demand of nearly 97%-98% individuals.

Adequate Intake (AI): This level of intake is established and assumed that it will fulfil nutritional requirements when sufficient data is not available to develop an RDA.

Estimated Average Requirement (EAR): It is intake level expected to fulfil the nutritional requirements of 50% of healthy people and generally it is used to plan nutrient intake for a group of people.

Tolerable Upper Intake Level (UL):  It is a maximum permissible daily intake so that any adverse health effects are avoided.

The table given below lists the current RDAs for pyridoxine. FNB developed an AI for infants from birth to 1 year age.

Age MaleFemalePregnancyLactation
Birth to 6 months (AI)0.1 mg0.1 mg
7–12 months (AI)0.3 mg0.3 mg
1-3 years0.5 mg0.5 mg
4-8 years0.6 mg0.6 mg
9-13 years1 mg1 mg
14-18 years1.3 mg1.2 mg1.9 mg2.0 mg
19-50 years1.3 mg1.3 mg1.9 mg2.0 mg
51+ years1.7 mg1.5 mg

Absorption

Vitamin B6 is predominantly absorbed in the small intestine (jejunum). After its absorption, the cells metabolize it to the active forms in the liver. The metabolization of Pyridoxine occurs inside the mitochondria and cytosol at a cellular level. After metabolism, excretion occurs by the kidney and the albumin-bound to the plasma. The half-life elimination exceeds 15-20 days.

Dietary Supplement

In the market, it is available as multivitamin (conjugated with other groups of the vitamin-B complex). Most commonly, it is available as pyridoxine hydrochloride. Its supplement is either available as capsule, tablet or solution. A body consumes a large amount of vitamin B6 and quickly eliminates most of it in the urine. Approximately 28-36% of the population uses supplements to overcome the deficiency of vitamin B6.

Deficiency of Vitamin B6

The deficiency of vitamin B6 is correlated with the lack of vitamin B12 and folic acid in our body.

Risk Factors

Its lack is generally uncommon, but may occur in individuals with the following factors:

  • Individuals with impaired renal function have low plasma PLP concentration.
  • People concurred with autoimmune disorders like rheumatoid arthritis, celiac disease, ulcerative colitis, and other malabsorptive diseases also results in low plasma PLP concentration.
  • Individuals addicted to alcohol are also having low net PLP concentration by the production of acetaldehyde through alcohol.

Signs and Symptoms

Infants: Seizures prevalently occurs in young vitamin B6 deficient people.
Adults: Rashes, mental status change, cheilitis, cracks in mouth corner, glossitis (swelling of tongue), depression are the common signs and symptoms that frequently seen in adults with vitamin B6 deficiency.
Sometimes normocytic, microcytic or sideroblastic anaemia may also occur in vitamin B6 deficient person.

Diagnosis

The vitamin B6 deficiency in a person can be diagnosed by looking into some of the clinically significant symptoms like:

Development of dermatitis, mental instability, the onset of sensory polyneuropathy in adults and seizures in infants are few some clinical manifestations that indicate a person can be Vitamin B6 deficient. After looking at the symptoms, clinical evaluation is essential, where the two methods are most commonly used to check whether a person is vitamin B6 deficiency or not.

  • Measurement of serum pyridoxal phosphate
  • Measuring urinary excretion of xanthurenic acid: Increase in the level of xanthurenic acid confirms inadequate active B6 for the synthesis of tryptophan.

Treatment

The deficiency can be overcome by taking a dietary supplement of vitamin B6 that is pyridoxine. It is generally available in the form of an oral capsule or tablet that can be given to the patient suffering from vitamin B6 deficiency as prescribed by the physician.

Overdose of pyridoxine may cause toxicity and leads to cause neuropathies, movement disorders, photosensitivity, nausea, heartburn, painful dermatological eruptions.

Functions

Metabolism of macronutrients

PLP and PMP are the coenzymes of vitamin B6 that carry out 100 of enzymatic reactions. These cofactors participate in the metabolism of an amino acid (particularly homocysteine); carbohydrate (gluconeogenesis and glycogenolysis); and lipid metabolism.

Haemoglobin production

PLP facilitates the haemoglobin production, as it functions as a cofactor for the enzyme ALA (Aminolevulinic acid) synthase. It enhances the oxygen-binding capacity of haemoglobin by binding to the two of the sites in haemoglobin.

Immune function

Both PLP and PMP plays a vital role in the proper functioning of the immune system by promoting the production of lymphocytes and interleukins.

Brain health

The cofactors of vitamin B6 also contributes to the brain heath or nervous system by producing the neurotransmitters (like serotonin and norepinephrine) and in forming myelin.

Gene expression

The increased and decreased level of vitamin B6 also aids in the expression of specific genes. For example, the reduced level of vitamin B6 leads to the increased gene expression of albumin mRNA.

Uses

According to the research, pyridoxine is found to be very effective against many health issues like depression, cancer, cardiovascular disease, and many more.

Depression

Vitamin B6 improves the symptoms of depression by producing neurotransmitters that can control emotions by producing serotonin, dopamine and gamma-aminobutyric acid.

Pyridoxine also controls the increased concentration of homocysteine in the blood and reduces the chances of depression and other psychiatric problems that may develop in an individual.

Cardiovascular disease

Pyridoxine conjugated with Vitamin B9 and B12 may regulate the level of increased homocysteine in the blood which may result into increased risk of heart and blood vessel diseases like blood clotting, the formation of free radical cells etc.

Cancer

There are no proper shreds of evidence to prove that Pyridoxine helps prevent cancer, but according to several studies, it is found to be effective, notably in treating gastrointestinal cancers.

It is believed that pyridoxine reduces the oxidative stress, the dispersion of tumour cells, and chronic inflammation, which in turn found to be effective in controlling colorectal cancer.

Morning sickness

It is the medical condition, where pregnant women encounter with symptoms like nausea and vomiting during their first few months of pregnancy. It generally persists for 20 days or more, which sometimes necessitates medical care as a result of severe dehydration.

According to the research, the combination of pyridoxine with an antihistamine complex (doxylamine) lowers the hospitalization rates and reduces the chances of nausea and vomiting in pregnant women.

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