Vitamin B6, also referred to as pyridoxine, is a water-soluble vitamin which was first isolated in the 1930s. It is naturally present in several foods and can also be consumed in the form of dietary supplements.
There are three forms of vitamin B6: pyridoxine (PN), pyridoxal (PL), and pyridoxamine (PM).
The principal coenzyme form, which is the most important in human metabolism, is the phosphate ester derivative pyridoxal 5′-phosphate (PLP).
Other forms of vitamin B6 are Pyridoxine-5-Phosphate, P5P, P-5-P, Adermine Hydrochloride, Chlorhydrate de pyridoxine, Pyridoxal, Piridoxina, Pyridoxal Phosphate, Adermine Chlorhydrate, and Pyridoxine HCl.
The role of Vitamin B6 in the body
In the coenzyme forms, vitamin B6 performs a wide array of different functions in the body and is highly versatile, wherein it is involved in more than 100 enzyme reactions that are mostly related with the metabolism of proteins.
PMP and PLP are both involved in amino acid metabolism, and PLP alone is involved with the metabolism of lipids, carbohydrates, and one-carbon units.
Vitamin B6 also plays a significant role in cognitive development through maintaining normal levels of amino acid homocysteine in the blood, and by the biosynthesis of neurotransmitters. It is also involved in the formation of hemoglobin; glycogenolysis and gluconeogenesis; and in the immune function as it promotes the production of lymphocyte and interleukin-2.
Pyridoxine Deficiency
Pyridoxine is used in the prevention and treatment of pyridoxine deficiency or having low levels of pyridoxine, and the so-called “tired blood anemia” that can result.
It is commonly used by women with menstruation problems such as premenstrual syndrome (PMS), depression related to pregnancy or due to birth control pills, nausea and vomiting (morning sickness) during early pregnancy, stopping the flow of milk after giving birth, and symptoms of menopause.
It is also used for high cholesterol, reducing blood levels of the amino acid homocysteine that is associated with heart disease, helping clogged arteries to stay open in angioplasty and for heart disease.
Vitamin B6 plays a significant role in both DNA and RNA synthesis, and in the overall function of the nervous system.
Vitamin B6 Deficiency
A deficit in vitamin B6 is extremely rare, although it is linked with symptoms such as seizures, skin changes, anemia, and other neurological disorders.
Inadequate amounts of vitamin B6 is often associated with low concentrations of the other B-vitamins such as folic acid and vitamin B12. As the deficiency progresses, biological changes become more obvious due to deficiency of this nutrient.
Insufficient intake of pyridoxine is associated with ermatitis with cheilosis or the cracks at the corners of the mouth and scaling on the lips; weakened immune function; glossitis or swollen tongue; electroencephalographic abnormalities; depression and confusion; and microcytic anemia. A vitamin B6 deficiency in infants can cause abnormally acute hearing, irritability, and convulsive seizures.
Vitamin B6 Recommended Dietary Allowance (RDA)
Due to the fact that vitamin B6 is involved in numerous metabolic functions, several factors can affect the requirement of this nutrient for an individual. The intake of protein is the most studied among all the other factors that can affect the daily requirement. In 1998, the Food and Nutrition Board (FNB) revised the current RDA for vitamin B6.
| Recommended Dietary Allowance (RDA) for Vitamin B6 | ||
| AGE | FEMALES (mg/day) | MALES (mg/day) |
| 0 to 6 months | 0.1 (AI) | 0.1 (AI) |
| 7 to 12 months | 0.3 (AI) | 0.3 (AI) |
| 1 to 3 years | 0.5 | 0.5 |
| 4 to 8 years | 0.6 | 0.6 |
| 9 to 13 years | 1.0 | 1.0 |
| 14 to 18 years | 1.2 | 1.3 |
| 19 years to 50 | 1.3 | 1.3 |
| 51 years and older | 1.5 | 1.7 |
| Pregnant | 1.9 | – |
| Lactating | 2.0 | – |
Dietary Sources of Vitamin B6
Some of the main vitamin B6 rich foods are banana, potato, tuna, lima beans, soybeans, pork loin, chicken breast, beef, sunflower seeds, chickpeas, beef liver, raisins, tofu, spinach, watermelon, onions, squash, and white rice.
Certain plant foods contain a particular vitamin B6 form which is the pyridoxine glucoside. However, this form appears to have only half the bioavailability of vitamin B6 from other sources.
References
Office of Dietary Supplements; LPI; University of Maryland Medical Center; Drexel University College of Medicine; New York University.