On Fri, 20 Apr 2007 09:30:29 -0600 in alt.support.diet.low-carb, "Pat"
<[email hidden]> wrote,
Quoted message said:
The product, made by Schiff, is called Melatonin Plus. It contains 3 mg of
melatonin, 25 mg of L-Theanine, and 10 mg of Vitamin B6 as pyridoxine
hydrochloride. He was taking a table a day, at bedtime.
That clarifies things, thanks. I misread your initial post.
I would guess that amount of B6 should be harmless to most people under
ordinary circumstances, so I cannot blame Schiff too much. Maybe he has
some unusual trouble metabolizing B6. Good luck.
For comparison, the following is quoted from
Nutritional Biochemistry of the Vitamins SECOND EDITION
DAVID A. BENDER
Cambridge Press, 2003 www.cambridge.org/9780521803885
9.6.4 Toxicity of Vitamin B6
Animal studies have shown that vitamin B6 is neurotoxic, causing
peripheral neuropathy, with ataxia, muscle weakness, and loss of balance
in dogs given 200 mg of pyridoxine per kg of body weight for 40 to 75
days, and the development of a swaying gait and ataxia within 9 days at
a dose of 300 mg per kg body weight (Phillips et al., 1978; Krinke et
al., 1980). At the lower dose of 50 mg per kg of bodyweight, there are
no clinical signs of toxicity, but histologically there is loss of
myelin in dorsal nerve roots. At higher doses, there is widespread
neuronal damage, with loss of myelin and degeneration of sensory fibers
in peripheral nerves, the dorsal columns of the spinal cord, and the
descending tract of the trigeminal nerve. The clinical signs of toxicity
after 200 to 300mg of vitamin B6 per kg of body weight regress within 3
months after withdrawal of these massive doses, but sensory nerve
conduction velocity, which decreases during the development of the
neuropathy, does not recover fully (Schaeppi and Krinke, 1982).
In 1983, sensory neuropathy was reported in seven patients who had
been taking between 2,000 to 7,000 mg of pyridoxine/day for several
months (Schaumburg et al., 1983). On withdrawal of the vitamin
supplements, there was considerable recovery of neuronal function,
although there was residual nerve damage in some patients.
There has been one report of the development, within 2 years, of sensory
neuropathy in an infant with vitamin B6-dependent seizures treated with
2,000 mg per day, but over the following 16 years, the neuropathy did
not progress (McLachlan and Brown, 1995). However, most reports of
patients with vitamin B6 dependency diseases (Section 9.4.3) do not
mention sensory neuropathy. One study has reported electrophysiological
and neurological examination of 17 homocystinuric patients who had been
treated with 200 to 500mg of vitamin B6 per day for 10 to 24 years;
there was no evidence of neuropathy (Mpofu et al., 1991).
None of the studies in which there has been objective neurological
examination has shown any evidence of sensory nerve damage at intakes of
vitamin B6 below 200mg per day. Most have shown adverse effects only at
considerably higher levels of intake.
Studies with cells in culture show a cytotoxic effect of vitamin B6.
This may be from the formation of cytotoxic products when the vitamin is
subjected to ultraviolet irradiation and may not be relevant in vivo
(Maeda et al., 2000).
9.6.4.1 Upper Levels of Vitamin B6 Intake
Although there is no doubt that vitamin B6 is neurotoxic in gross
excess, there is considerable controversy over the way in which
toxicological data have been translated into limits on the amounts that
may be sold freely as nutritional supplements. This appears to have been
achieved by the application of standard toxicology safety margins, and
taking as the upper safe limit of intake 1% of the no adverse effect
level. Whereas this is appropriate for setting limits on additives and
contaminants, it can be argued that it is not appropriate as a basis for
setting limits on a nutrient; for many nutrients, an upper limit of
intake established in this way would be below the average requirement to
prevent deficiency.
There is little evidence that intakes of up 200 to 500 mg of vitamin B6
per day for prolonged periods are associated with any adverse effects.
The U.S. Food and Nutrition Board set a tolerable upper level for adults
of 100 mg per day (Institute of Medicine, 1998); the European Union
(Scientific Committee on Food, 2000) set 25 mg per day
Referenced above:
Schaumburg H, Kaplan J, Windebank A, Vick N, Rasmus S, Pleasure D, and
Brown MJ (1983) Sensory neuropathy from pyridoxine abuse. A new
megavitamin syndrome. New England Journal of Medicine 309, 445–8.
McLachlan RS and Brown WF (1995) Pyridoxine dependent epilepsy with
iatrogenic sensory neuronopathy. Canadian Journal of Neurological
Science 22, 50–1.
Mpofu C, Alani SM, Whitehouse C,Fowler B,and Wraith JE (1991) No sensory
neuropathy during pyridoxine treatment in homocystinuria. Archives of
Disease in Childhood 66, 1081–2.
Institute of Medicine (1998) Dietary Reference Values for Thiamin,
Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid,
Biotin and Choline. Washington, DC: National Academy Press.
