Re: [OT] Pre-pregnant? I think I'm gonna pre-puke


"John F. Eldredge" <john@xxxxxxxxxxxxxx> wrote in message
news:5h0s72d9fc5cibti4fph3r1una0i2pjc4f@xxxxxxxxxx
On Sun, 28 May 2006 22:14:49 -0500, "Howard C. Berkowitz"
<hcb@xxxxxxxxxxxx> wrote:


RDAs and MDAs are "nutritional" values for the amount needed to perform
normal bodily functions. There is another category, called
"pharmacologic"
dose, at which the vitamin is being used for a different effect. For
example, niacin is an essential B vitamin. In very large doses, however,
it
can have excellent effects on blood lipids (cholesterol and associated
substances).

At pharmacologic doses, even water-soluble vitamins, such as the B
complex,
can have unexpected toxicity. Frequently, taking a pharmacologic dose of
niacin causes an intense hot flash that some people can't tolerate (I
found
it pleasant0. I was unable to continue the dose, because I had a rare
skin
reaction called acanthosis nigricans -- areas of skin would turn brown to
black, get leathery, and crack and bleed. Stopping the niacin therapy
made
this go away--but while I was taking it, it did wonderful things for
cholesterol. Doses this large also can affect the liver.

It's not wise to take megadoses of vitamins without having laboratory
monitoring -- we _think_ several vitamins have no toxic level, but we
don't
know. There are truly strange things, as in the B vitamin pyridoxine can
cause nerve inflammation both at inadequate and very large doses.


My cardiologist told me that large doses of niacin could help my
cholesterol readings, but would also make it difficult for me to
control my blood sugar (I am diabetic), so he would be reluctant to
prescribe it without approval from my endocrinologist.

That's reasonable. People should think of large (i.e., pharmacologic) doses
of vitamins as drugs, with all the potential interactions and side effects.
I become concerned when I hear megadoses of vitamins assumed to be harmless
as "food supplements".

In general, the water-soluble vitamins (B, C, K) are nontoxic, with
exceptions such as niacin and pyridoxine. Fat-soluble vitamins, such as A,
D, and E are much more likely to be toxic, although E is probably safe in
most cases. Polar bears, for example, concentrate so much A in their livers
that the liver is poisonous to humans.


.

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