Nutrition Expert: Saba Shaikh, Practising Clinical Nutritionist, Mumbai.
- Pyridoxine (Vitamin B6)
Pyridoxine is the 4-methanol form of vitamin B6, an important water-soluble vitamin that is naturally present in many foods. As its classification as a vitamin implies, Vitamin B6 (pyridoxine) is essential nutrient required for normal functioning of many biological systems within the body.
Vitamin B6, principally in its biologically active coenzyme form pyridoxal 5′-phosphate, is involved in a wide range of biochemical reactions, including the metabolism of amino acids and glycogen, the synthesis of nucleic acids, hemogloblin, sphingomyelin and other sphingolipids, and the synthesis of the neurotransmitters serotonin, dopamine, norepinephrine and gamma-aminobutyric acid.(1)
- The Immune System
The immune system’s role is crucial in prevention and control of pathogenic infection as well as various cancers. Meanwhile, the natural aging process, malnutrition, and increased stress brought upon by the fast-paced urban lifestyle have been demonstrated to decrease immunity. Among these factors, the effect of malnutrition on immunity has been widely investigated on children in developing countries, people with eating-disorder problems, and the elderly. Close to one billion people suffer from varying degrees of malnutrition as a result of insufficient food or food lack of micronutrient. (2)
- Vitamin B6 and Immunity
Vitamin B6 is an intriguing micronutrient that mediates numerous metabolic processes in vivo including amino acid metabolism, gluconeogenesis, lipid metabolism, and nervous system development and functioning. Vitamin B6 has been implicated in the regulation of immune responses that are associated with a wide range of diseases, including inflammation and various cancers.
Vitamin B6 deficiency is a very common phenomenon, especially among women of childbearing age as well as the elderly. (2)
Vitamin B6 acts as co-factor for certain enzymes that helps in carrying out their respective functions. Vitamin B6 contains 3 pyridine derivatives therefore it is named as pyridoxine. Vitamin B6 helps control levels of homocysteine a common amino acid in the blood. Higher level of homocysteine (hyper-homosysteinaemia) is associated with heart diseases like Acute Coronary Syndrome (ACS) and cardiovascular death, collectively called athero-thrombosis. The body needs B6 in order to absorb vitamin B12 and to make red blood cells and cells of the immune system. Vitamin B6 helps the body to make several neurotransmitters like serotonin, chemicals that carry signals from one nerve cell to another. Serotonin is only synthesized by the tryptophan and this conversion of tryptophan to serotonin occurs in the presence of pyridoxal phosphate which is a vitamin B6 derivative. Vitamin B6 is needed for normal brain development and function, and helps the body to make nor-epinephrine, which influences the mood, and melatonin, that helps in regulating the body clock. (3)
Vitamin B6 helps to improve immune response to increase the production of antibodies and also helps in communicative interactions between cytokines and chemokines. Vitamin B6 deficiency reduces the lymphocyte growth and proliferation, antibody formation and T-cell activity. (3)
- Vitamin B6 Deficiency
Vitamin B6 deficiency is rare in isolation and usually found in association with other B vitamin deficiencies such as folic acid and B12.
Low plasma levels of active B6 are found in chronic alcohol dependence, with obese states, pregnancy, preeclampsia and eclampsia, and malabsorptive states such as celiac, inflammatory bowel disease, and bariatric surgery.
Additional at-risk groups with inadequate intake or increased metabolic requirements may become functionally deficient in B6. Included in this group are those with renal impairment, autoimmune disorders, and chronic alcohol use. Patients with chronic renal failure, especially those receiving hemodialysis or peritoneal dialysis, have low plasma levels of B6. Autoimmune disorders, such as rheumatoid arthritis, have increased catabolism of B6, resulting in higher demand for dietary supplementation of B6. (4)
- Sources of Pyridoxine (B6)
Beef liver, chickpeas, tuna, salmon, rice, cereals, onions (3)
- Dietary Supplements
The human body cannot store B6, and thus a daily source is required. There appears to be a bioavailability preference for meat over plant source B6. This may be important to those who favor a plant-based diet exclusively. These individuals may need added supplementation. The major supplement in multivitamins is a pyridoxine hydrochloride. Dietary intake and the bioavailability of ingested B6 may vary, as well as the urinary excretion. (4)
Vitamin B6 is available in multivitamins, in supplements containing other B complex vitamins, and as a stand-alone supplement. Absorption of vitamin B6 from supplements is similar to that from food sources and does not differ substantially among the various forms of supplements.(5)
Recommended Dietary Allowances (RDAs) for Vitamin B6
|Age||Vitamin B6 (mg/d)|
|Infants (0-6 months)||0.1|
|Men (sedentary work)||2.0|
|Men (Moderate work)||2.0|
|Men (Heavy Work)||2.0|
|Women (sedentary work)||2.0|
|Women (Moderate work)||2.0|
|Women (Heavy Work)||2.0|
|Lactating Women(0-6 months)||2.5|
|Lactating Women(6-12 months)||2.5|
Source: Nutrient Requirements and Recommended Dietary Allowances for Indians (ICMR 2010)