Vitamin B6 is a water-soluble vitamin that is involved in over 100 different enzymatic reactions in the body. Many of these are related to amino acid synthesis, fatty acid metabolism and hemoglobin synthesis. Without enough hemoglobin from a vitamin B6 deficiency, the body’s ability to transport oxygen is decreased and anemia results.
Vitamin B6 also is critical for the release of glucose from glycogen stores; this is why fatigue is one of the symptoms of a deficiency. The vitamin is also important for the synthesis of serotonin and dopamine.
The immune system, heart and blood vessels, detoxification (methylation) and cognitive health are dependent on vitamin B6.
A vitamin B6 blood test helps determine whether or not someone is deficient in the vitamin, or has high levels. It can give the doctor clues about anemia, heart disease, lack of energy and skin problems.
Normal Ranges for Vitamin B6 in mcg/L:
Adults: 5-50 mcg/L
Critical Range: <5 or >50 mcg/L
Vitamin B6 deficiency is characterized by symptoms such as:
- Inflamed tongue
- Skin disorders
- Mouth sores
- Sores at the corners of the mouth
- Morning sickness in pregnant mothers
Chronic inflammation results in the body when vitamin B6 levels are low. Inflammation that is systemic (throughout the whole body) may be related to cancer, heart disease, PMS, carpal tunnel syndrome, and dementia. When there’s a vitamin B6 deficiency, homocysteine levels will rise as a result and increase the risk for heart disease.
Some specific causes of low vitamin B6 might be:
- Malabsorption of the vitamin in the GI tract due to GI diseases
- Chronic alcoholism
- Sickle cell disease
- Kidney stones containing oxalates
- Kidney dialysis
- Rheumatoid arthritis
- Liver cancer
- Medications such as ones for Parkinson’s disease, tuberculosis, birth control pills, and non-steroidal anti-inflammatory drugs interfere with vitamin B6 metabolism.
Consuming vitamin B-6 through food appears to be safe, even in excessive amounts.
When used as a supplement in appropriate doses, vitamin B-6 is likely safe.
However, taking too much vitamin B-6 from supplements can cause:
Recommendations regarding the daily intake of vitamin B6 in adults are 1.4 mg/day for women and 1.6 mg/day for men with slightly different recommendations for infants, children, adolescents, pregnant and breast-feeding women.
Daily vitamin B6 intake should not exceed 25 mg as an intake of 50 mg/day is associated with neurological side effects. Thereby, pyridoxine, the main B6 vitamer in dietary supplements, is supposed to be the main driver of vitamin B6 toxicity. Elevated plasma vitamin B6 levels are associated with sensory and peripheral neuropathy, leading to progressive sensory ataxia, unstable gait, numbness of the hands and absent tendon reflexes. Furthermore, photosensitivity and mild motor neuropathy have been reported. [L]
Of note, both vitamin B6 intoxication and vitamin B6 deficiency can lead to neuropathy, as in both cases PLP-dependent enzymes are inhibited by pyridoxine.
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