WHAT IS VITAMIN B6?
As with the other B vitamins, Vitamin B6 is an essential water-soluble vitamin1 that our body cannot synthesize by itself. We must acquire it through diet supplementation. Vitamin B6 actually refers to a family of different compounds2 consisting of pyridoxine, pyridoxal, and pyridoxamine, along with their associated 5’-phosphate esters. Pyridoxamine 5’ phosphate (PMP) and pyridoxal 5’ phosphate (PLP) are the active co-enzyme forms of vitamin B6, with PLP being the biologically active form contained in our product.
As a coenzyme, vitamin B6 as PLP is particularly important for catalysis of protein, carbohydrate and lipid metabolism1. It is also important for child brain development throughout pregnancy3 and during infancy4 through its role in the biosynthesis of neurotransmitters. Vitamin B6 also plays a significant catalytic role in the synthesis of cysteine5 (the importance of which we have discussed in the methionine article ) as well as the antioxidant glutathione peroxidase6.
Good dietary sources7 of vitamin B6 include:
- Beef liver
- Fresh tuna
- Sockeye salmon
- Chicken and turkey
WHY IS VITAMIN B6 IN MY PRODUCT?
The recommended daily allowance of vitamin B6 for females is between 1.2 and 1.5 mg/day7, increasing to 1.9 mg/day during pregnancy and 2.0 mg/day while lactating. While most of the US population will achieve adequate levels of Vitamin B6 through a healthy diet, certain at-risk groups have been identified8, including smokers, African-Americans, seniors, and current and/or former users of oral contraceptives.
There are a plethora of general health benefits to maintaining adequate levels of vitamin B6. For example, a review of studies regarding the efficacy of vitamin B6 in reducing the symptoms of premenstrual syndrome suggested a benefit9 of doses up to 100 mg/day (which is 50 times more than RDA) for the treatment of premenstrual symptoms and premenstrual depression. A more recent randomized control trial has echoed these results10.
A deficiency in vitamin B6 has been linked to several different diseases11 and conditions, including autism, schizophrenia, Alzheimer’s disease, Parkinson’s disease, epilepsy, Down’s syndrome, diabetes, and cancer. Evidence points to the deficiency leading to damage to our DNA12 and eventually resulting in the spawning of cancerous cells. Studies have indicated a link between vitamin B6 deficiency and colorectal cancer13. Another systematic review also suggested the potential of vitamin B6 in the prevention of cancers 14, and especially gastrointestinal cancers, but the evidence was not quite as strong.
There is substantial evidence for a link between vitamin B6 deficiencies and diabetes15, in particular, gestational diabetes (that occurs during pregnancy but disappears after birth) and the far more common type 2 diabetes.
Evidence also exists towards the benefits of the B vitamins and in particular vitamin B6 as a preventative measure for symptoms of incident depression16 in older adults followed on average over a 12 year period. Other neurological benefits have been observed in terms of cognitive function and its decline in older subjects. A fairly recent study showed that lower dietary and biomarker measured baseline levels of vitamin B6 predicted a greater than expected rate of cognitive decline over a 4-year period. The authors concluded that vitamin B6 might be an important protective factor for the maintenance of cognitive health during aging17. A similar study also found that a higher intake of the B vitamins throughout young adulthood was linked with better midlife cognitive function18. The importance of vitamin B6, as well as all the other members of the vitamin B family in terms of their effect on brain function, have been well summarized.19
Another study has indicated a beneficial effect of vitamin B6 (and folate as well) in the prevention of death as a result of stroke, coronary heart disease, and heart failure20 amongst a sample of ~59000 Japanese participants. Deficiency in vitamin B6 has also been linked to an increased likelihood of atherosclerosis21 - the building up of plaque on artery walls leading to high blood pressure.
Other general beneficial health effects of vitamin B6 include its role as an anti-inflammatory agent22 as well as an antioxidant23.
Despite all these general health benefits, it should be cautioned that there is evidence that high doses24 of vitamin B6 can be neurotoxic25 and susceptible to UVA-induced phototoxicity26. Follow-up studies, however, showed that all of the vitamin B6 compounds demonstrated these phototoxic effects with the exception of that which is in our product, pyridoxal phosphate27.
Another isolated study has shown how oral administration of vitamin B6 helps prevent hair loss in mice31 induced by exposure to cigarette smoke, while another somewhat random study showed how vitamin B6, in conjunction with azelaic acid, improved hair growth and hair thickness32 in mice. In humans, there is a suggestion that the role of vitamin B6 in the synthesis of cysteine is an important factor in menopausal women in terms of their rate of hair growth33 and hair diameter.
To summarize, the benefits of vitamin B6 are largely geared more towards general health, with sufficient documented links to various diseases shown that should convince everyone of the importance of maintaining adequate levels. Even though you may think your dietary intake is sufficient, there is evidence showing that insufficient levels in the USA are more common than one might believe. Specific risk groups have been identified, including those women taking oral contraceptives, while pregnant or lactating mothers should also be particularly cognizant of their intake. Relief of the symptoms of premenstrual syndrome has also been suggested, while the long-term benefits in terms of cognitive function appear well documented. A word of caution to conclude - there is evidence of neuro- and phototoxicity at high levels of ingestion, so one should keep their levels below the recommended upper limit of 100 mg/day7.