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Vitamins B6
(Pyridoxine)
DESCRIPTION
Vitamin B6 is a well-known member of the water-soluble B vitamins.
Besides pyridoxine, two other variations on B6 exist - namely
pyridoxal and pyridoxamine. All three forms exist routinely
in animal and plant foods and have equal vitamin B6 activity.
STABILITY
Vitamin B6 is fairly resistant
to heat but may leach out into water and is also lost by exposure
to alkalis or ultraviolet light.
FUNCTIONS
Vitamin B6 is rapidly converted
in the body to the coenzymes pyridoxal phosphate and pyridoxamine
phosphate. These coenzymes play an essential role in protein
metabolism and also function in energy production, fat metabolism,
central nervous system activity and haemoglobin production.
Involved in the conversion of Essential Fatty Acids to prostaglandins,
which help regulate hormone balance. It helps to stablisise
fluid levels through Potassium /Sodium balance.
DEFICIENCY
The administration of a
vitamin B6 antagonist to the diet of human volunteers produced
symptoms of seborrhoea (oily Skin with crusts and scales)
around the Eyes, nose and mouth. There was also a lowering
of white blood cell count and a loss of ability to convert
tryptophan to nicotinic acid. A type of Anaemia was also noted.
REQUIREMENTS
Upper safe level for daily
supplementation = 200mg
Recommended Daily Allowance
= 2mg
Individuals with high intakes
of protein will need more vitamin B6 in the diet.
SUPPLEMENTAL USES
The Pill and HRT:
Many women on the contraceptive pill find vitamin B6 is a
useful supplement to take as it can help alleviate the Depression
sometimes associated with taking this medication (1).
Drinkers and Smokers:
People who smoke or drink large quantities of alcohol would
benefit from a supplement of vitamin B6 as these activities
deplete the nutrient (2).
PMS:
Supplemental vitamin B6 can also be useful in the treatment
of Pre-menstrual syndrome (3) and is used by many women for
this purpose. Studies in this area have conflicting results,
but 50-200 mg daily does seem to be generally of benefit.
Sickness:
Vitamin B6 has been used for the prevention and treatment
of nausea and Vomiting due to morning sickness (4) irradiation,
drug therapy, anaesthesia and travel sickness, but a good
response is not always seen.
SAFETY
2-7g vitamin B6 daily may
bring about the development of sensory neuropathy (numbness
and tingling of nerves in the extremities). Such symptoms
have also been reported in women taking as low as 50mg daily,
but these reports have since largely been discredited. All
cases of peripheral neuropathy disappeared within six months
on withdrawal of the vitamin.
INTERACTIONS AND CONTRA-INDICATIONS
Levadopa:
Vitamin B6 is not compatible with this medication for Parkinson’s
disease.
Phenytoin and Phenobarbitone:
These anticonvulsant medicines should not be used in conjunction
with vitamin B6.
It is usually recognised
that B vitamins are best taken together for most general purposes.
However, there is no detriment in taking vitamin B6 singly
for a specific reason.
FOOD SOURCES
Food (mg/100g)
Wheatgerm 0.95
Bananas 0.51
Turkey 0.44
Chicken 0.29
Fish, white 0.29
Brussels sprouts 0.28
Beef, stewing steak 0.27
Potatoes 0.25
Baked beans 0.12
Bread, wholemeal 0.12
Peas, frozen 0.10
Bread, white 0.07
Oranges 0.06
Milk 0.06
The main sources of vitamin
B6 in the diet are potatoes and other vegetables, milk and
meat.
REFERENCES
1. Villegas Salas E. et
al, Effect of vitamin B6 on the side effects of a low-dose
combined oral contraceptive. Contraception, ,55;4:245-248,
1997.
2, Fonda ML, Vitamin B6 metabolism and binding to proteins
in the blood of alcoholic and nonalcoholic men. Alcohol Clin
Exp Res,17;6:1171-1178, 1993.
3. Campbell EM et al, Premenstrual symptoms in general practice
patients. Prevalence and treatment. J Reprod Med,42;10:637-646,
1997.
4. Erick M, Vitamin B-6 and Ginger in morning sickness. J
Am Diet Assoc, 95;4:416, 1995.
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