Vitamin A and pregnancy.
Should you be concerned?
Hi. I'm Dr. Chris Masterjohn of
chrismasterjohnphd.com. And this is
Chris Masterjohn Lite, where the name of the game is
"Details? Shmeetails. Just tell me what works!"
And today we're going to talk about
vitamin A and pregnancy. In the last few episodes, I've
been talking about vitamin A toxicity,
but there are concerns that too much
vitamin A in pregnancy, even at levels
that are not toxic to the mother, could
cause birth defects in the baby. This is
based on several things. First of all, we
know from animal experiments that both
vitamin A deficiency and vitamin A
toxicity will cause birth defects. Second,
there was a study published in 1995 that
looked at what do women consume now for vitamin A,
and then looked at in the future what
happens to the risk of birth defects.
That's called a prospective study
because they looked at the vitamin A first
and looked at the outcome later. And that
showed that women who consume more than
10,000 IU a day in the first eight weeks
of pregnancy had an increased risk of
birth defects. There were a number of
other studies published that showed that
much higher vitamin A intakes had no
effect or were even associated with
lower risk of birth defects, but they
were all retrospective, which means that
after the birth defects were determined,
then they asked the mothers how much
vitamin A did they eat leading into their
pregnancy. And those are considered
to have a greater risk of bias and to be
less accurate because it's -- there's more --
you're more likely to be biased or to
not remember correctly what you ate before
than to know what you're eating now
and to correctly report what you're eating now.
The 1995 paper got a lot of
criticism because there were a lot of
things that seemed to be off about the
paper. And I actually did a write-up of
this that I'll link to in the description of this episode.
It was a sidebar in an article that I wrote
called "Vitamins for Fetal Development."
So, I'll refer you to that article if you
would like more information about the
controversy. Suffice it to say that there
really isn't very good data about
whether we should be concerned about
vitamin A intakes around 10,000 IU
leading into the first eight weeks of
pregnancy, but there's also not that
great reason to get more than that if
there are no signs and symptoms of
vitamin A deficiency in the mother.
So, the way that I look at this is, you
should cap, if you are of
childbearing age and planning to get
pregnant in the next year, you should cap your
vitamin A intake at 10,000 IU per day
and keep it below that, unless you have a very
good justification for doing otherwise.
And the reason is simple.
If you look at traditional diets, there are
some outliers where there are some
traditional diets where the vitamin A
intakes were higher than that. For
example, the Greenland Inuit. There was
one report of them consuming around 50-
or 60,000 IU per day, but overwhelmingly
across the board traditional diets
didn't go anywhere near that high. If you
think about eating liver once or twice a
week, and eating three eggs a day, and
eating three servings of high-quality
dairy every day, which are going to be
your major sources of retinol, the animal
form of vitamin A, you're not going to go
over 10,000 IU per day. And if you look
at the traditional use of cod liver oil,
you had some cases where
traditionally people used it in
tablespoon amounts when they were sick,
but they never did so for more than a
few days, and then you had other cases
where cod liver oil spread across the
world becoming very popular in medicine
using it in amounts of one or two
teaspoons a day for a period of weeks or
months, but not using it even in those
doses for an extended period of years.
The ability to take a vitamin A
supplement providing 10, 20, 30, 40, 50
thousand IU of vitamin A per day is
relatively speaking in human history a
very new thing, and it doesn't have a
great track record to speak of whether
it's safe or not to take during
pregnancy. So, the way that I look at it
is for a woman of childbearing age who
has a plan at some point in the next
year to become pregnant and doesn't
have any signs or symptoms of vitamin A,
of vitamin A deficiency, then limit the
vitamin A intake primarily to foods
rather than supplements. A supplement of
liver capsules or cod liver oil I think
is fine, but just keep the total under 10,000 IU per day.
For someone who has signs and
symptoms of vitamin A deficiency who has
blood work justifying a concern about
vitamin A deficiency, then I think it's
okay to go higher, but use the minimal
effective dose to resolve those and try
not to go higher than you need. Not
because I'm convinced that doing so will
cause birth defects, but because why take
the risk when there's no theoretical
benefit to come with it.
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All right, I hope you found this useful.
Signing off, this is Chris Masterjohn
of chrismasterjohnphd.com. This has been
Chris Masterjohn Lite.
And I will see you in the next episode.