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Vitamin
B6
Also Known
As
Pyridoxine
Physiology
and Clinical Effects
Vitamin B6 is the master vitamin in the processing of amino acids—the
building blocks of all proteins and some hormones. Vitamin B6 helps to
make and take apart many amino acids and is also needed to make serotonin,
melatonin, and dopamine. Vitamin B6 also aids in the formation of several
neurotransmitters and is therefore an essential nutrient in the regulation
of mental processes and possibly mood. To some extent, vitamin B6 lowers
homocysteine levels—a substance that has been linked to heart disease,
stroke, osteoporosis, and Alzheimer’s disease.
A link between
vitamin B6 deficiency and carpal tunnel syndrome has been reported in
some,1 but not all, research.2 3
Food
Sources
Potatoes, bananas, raisin bran cereal, lentils, liver, turkey, and tuna
are all good sources of vitamin B6.
Deficiency
Risk and Symptoms
Vitamin B6 deficiencies, although very rare, cause impaired immunity, skin
lesions, and mental confusion. A marginal deficiency sometimes occurs in
alcoholics, patients with kidney failure, and women using oral
contraceptives. Many doctors believe that most diets do not provide
optimal amounts of this vitamin.
Recommended
Dosage
The most common supplemental intake is 10–25 mg per day; however, higher
amounts (200–500 mg per day) may be recommended for certain conditions.
Contraindications
Although side effects from vitamin B6 supplements are rare, at very high
levels (200 mg or more per day) this vitamin can eventually damage sensory
nerves, leading to numbness in the hands and feet as well as difficulty
walking. Vitamin B6 supplementation should be stopped if any of these
symptoms begin to develop.
Pregnant and
lactating women should not take more than 100 mg of vitamin B6. For other
adults, vitamin B6 is usually safe in amounts of 200–300 mg per day,4
although occasional problems have been reported in this range.5
Any adult taking more than 100–200 mg of vitamin B6 for more than a few
months should consult a doctor. Side effects from vitamin B6 are dependent
on the level of intake. No one should ever take more than 500 mg per day,6
even with clinical supervision.
Since vitamin
B6 increases the bioavailability of magnesium, these nutrients are
sometimes taken together.
References:
1. Keniston
RC, Nathan PA, Leklem JE, Lockwood RS. Vitamin B6, vitamin C, and carpal
tunnel syndrome. J Occup Environ Med 1997;39:949–59.
2. Franzblau A, Rock CL, Werner RA, et al. The relationship of vitamin B6
status to median nerve function and carpal tunnel syndrome among active
industrial workers. J Occup Environ Med 1996;38:485–91.
3. Smith GP, Rudge PJ, Peters TJ. Biochemical studies of pyridoxal and
pyridoxal phosphate status and therapeutic trial of pyridoxine in patients
with carpal tunnel syndrome. Ann Neurol 1984;15:104–7.
4. Gaby AR. Literature review & commentary. Townsend Letter for
Doctors June 1990;338–9.
5. Parry G, Bredesen DE. Sensory neuropath with low-dose pyridoxine. Neurology
1985;35:1466–8.
6. Schaumburg H, Kaplan J, Windebank A, et al. Sensory neuropathy from
pyridoxine abuse. N Engl J Med 1983;309(8):445–8.
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