From the Guidelines
Vitamin B6 plays a crucial role in numerous bodily functions, including protein metabolism, red blood cell formation, brain development, immune function, and the production of neurotransmitters, with a recommended daily intake of 1.3-1.7 mg per day for adults, although recent studies suggest that elderly individuals may require higher intakes of 3-4.9 mg per day to avoid deficiency and hyperhomocysteinaemia 1. The role of Vitamin B6, also known as pyridoxine, is multifaceted, involving various physiological processes such as amino acid metabolism, haeme synthesis, neurotransmitter production, and hormone regulation 1.
Key Functions of Vitamin B6
- Amino acid metabolism: Vitamin B6 serves as a cofactor for numerous enzymatic reactions, including transaminations, racemizations, decarboxylations, and aldol cleavage, affecting carbohydrate, protein, and lipid metabolism 1.
- Red blood cell formation: Vitamin B6 is essential for the production of hemoglobin, a protein that carries oxygen in red blood cells.
- Brain development and function: Vitamin B6 is involved in the synthesis of neurotransmitters, such as serotonin and dopamine, which play critical roles in mood regulation, appetite, and sleep.
- Immune function: Vitamin B6 is necessary for the proper functioning of the immune system, with deficiency potentially leading to weakened immunity.
Dietary Sources and Requirements
Good dietary sources of Vitamin B6 include poultry, fish, potatoes, chickpeans, bananas, and fortified cereals. While the recommended daily intake for adults is 1.3-1.7 mg per day, recent studies suggest that elderly individuals may require higher intakes to avoid deficiency and related health issues, such as hyperhomocysteinaemia 1.
Potential Health Benefits and Risks
Vitamin B6 deficiency can cause anemia, depression, confusion, weakened immunity, and skin problems. Supplements may be recommended for certain conditions like morning sickness, carpal tunnel syndrome, or PMS symptoms, typically at doses of 50-100 mg daily. However, long-term high-dose supplementation (over 100 mg daily for extended periods) should be avoided as it can cause nerve damage 1. If considering supplementation, it's best to consult with a healthcare provider first to determine appropriate dosing. Recent investigations do not support any association between protein intake and vitamin B6 status in both elderly men and women, suggesting that vitamin B6 requirements may not be directly linked to protein intake 1. Data from depletion/repletion studies in the healthy elderly indicate an extended physiological range of function for vitamin B6 that is observed in response to increased levels of intake, highlighting the potential need for higher vitamin B6 intakes in this population 1.
From the Research
Role of Vitamin B6
Vitamin B6, also known as pyridoxine, plays a critical role in many biochemical and physiological processes in the human body 2. The biologically active form of vitamin B6 is pyridoxal 5'-phosphate (PLP), and a plasma PLP concentration above 30 nmol/L is indicative of an adequate vitamin B6 status for all age and sex groups 2.
Biochemical Reactions
Vitamin B6 is involved in:
- Amino acid and homocysteine metabolism
- Glucose and lipid metabolism
- Neurotransmitter production
- DNA/RNA synthesis 3
- Over 150 biochemical reactions, including the metabolism of carbohydrates, lipids, amino acids, and nucleic acids 4
Health Implications
- Vitamin B6 deficiency may be associated with various diseases, such as:
- Vitamin B6 deficiency may also induce chromosomal damage and hepatic lipid peroxidation in offspring 5
- High levels of vitamin B6 may lead to the development of peripheral neuropathy (PN) 6
Supplementation
- PLP-based supplements are preferred over pyridoxine supplements due to minimal neurotoxicity observed in neuronal cell viability tests 2
- Weekly administration of vitamin B6 supplements is preferred over daily use to prevent toxicity 2
- Supplementation with vitamin B6, even as part of a nutritional multivitamin supplement, has not been proven harmful at permitted daily doses in patients who already suffer from PN 6