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Knowledgebase Article
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Vitamin B6: Clinical guidelines
Clinical significance and functions of vitamin B-6
The Vitamin B ‘family’ includes many derivatives. One of those is vitamin B-6, delivered most commonly as pyridoxine phosphate, or PLP.
Its primary role is as a cofactor for over 100 enzymes related to amino acid metabolism.
PLP is involved in changing homocysteine to cysteine, the production of heme (a component of hemoglobin), the production of niacin from tryptophan, and the production of neurotransmitters, particularly serotonin.
It binds to steroid hormone receptors in cells, weakening their effects.
Vitamin B-6 supplementation may be advisable in:
1. Individuals with an elevated homocysteine level (over 9.0). Homocysteine is an amino acid formed when methionine donates a methyl group for DNA synthesis. Homocysteine can either be converted back to methionine through a pathway that requires folic acid and vitamin B12 or converted to cysteine through a pathway that involves two enzymes which require PLP.
2. Individuals taking certain pharmaceutical drugs for an extended period of time. Some medications shown to deplete vitamin B-6 include:
a. isoniazid
b. certain antibiotics
c. diuretics
d. theophylline
e. L-dopa and other drugs for Parkinsons disease
3. Possibly individuals with carpal tunnel syndrome, PMS, and morning sickness.
4. Pregnant women experiencing nausea (‘morning sickness’). Vitamin B-6 has been repeatedly demonstrated as an excellent treatment to reduce or eliminate this aggravating syndrome.
A note on toxicity:
Vitamin B-6 is the first water-soluble vitamin to demonstrate toxicity. While anecdotally quite rare, a few women using large doses of the vitamin in an attempt to alleviate PMS symptoms developed sensory neuropathies or numbness and tingling in their feet and hands, ironically a symptom of deficiency of vitamin B6. When the large doses of the vitamin was discontinued the symptoms went away, but in a couple of cases, the nerve damage was permanent.
The Food and Nutrition Board has set a clinically efficient treatment dosage of 100 mg for vitamin B-6 to prevent toxic side effects.
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