We cannot deny the importance of vitamin D. It's clearly an important part of
the immune system, for short term and long term issues. We found that children
with higher vitamin D amounts are less likely to be hospitalized for RSV. There
is an association of low vitamin D levels with lupus, MS, Rheumatoid arthritis,
diabetes (one and two), colon, breast and prostate cancer, cardiovascular
disease, hypertension, and preterm labor. It probably explains the seasonal
variation in influenza. There is probably a link between vitamin D and obesity.
I can go on, but it's hard to keep up.
We thought that vitamin D didn’t cross into breastmilk and if it did, it was in
low amounts. Of course if mom is insufficient, so is her milk. Vitamin D crosses
just fine when moms have sufficient amounts of vitamin D. One of the first
studies I saw (at a presentation, given by the author) about supplementing
mother/ infant breastfeeding dyads was out of the Medical University of South
Carolina. I was struck by how many of the mothers they enrolled were
insufficient in vitamin D. Now I get it- we’re not a sunshine-y state here
in Wisconsin. But South Carolina? As a good friend explained: “we like
our air conditioning.” That’s it then, isn’t it? We have gone from being
outside to being inside. Our lifestyle has changed.
And what about this “it’s a fat soluble vitamin- don’t take too much” caveat
that was drilled into me throughout medical school? Well, problem one:
it’s not a vitamin, it a hormone. Two: while it may be fat soluble, it’s
regulated like a hormone and it takes a ton of it to become dangerous. The
reports of vitamin D toxicity involve doses in the hundreds of thousands of
international units (IU) over weeks or months.
The best source of vitamin D is the sun. When you get increasing amounts
of vitamin D activated by the absorption of ultraviolet radiation from the sun,
things like sunscreen, and increased melanin pigment (a tan!) make it harder to
absorb. People with naturally darker skin therefore need more vitamin D. And
vitamin D is hard to get from food.
To summarize: Vitamin D is important. It comes from the sun. When there
is little sun, we need to supplement.
The disagreement is not whether we need it. We disagree on the dose since, as
research is done, the dose is constantly changing.
From the Endocrine Society:
- Infants and children ages 0-1 year require at least 400 IU/day (IU=25 ng)
of vitamin D and children 1 year and older require at least 600 IU/day to
maximize bone health. To raise the blood level of vitamin D consistently
above 30 ng/ml may require at least 1,000 IU/day of vitamin D;
- Adults aged 19-50 years require at least 600 IU/day of vitamin D to
maximize bone health and muscle function and at least 1,500-2,000 IU/day of
vitamin D may be needed to maintain blood level of vitamin D above 30 ng/ml;
- Adults aged 50-70 years and adults older than 70 years require at least
600 IU/day and 800 IU/day respectively of vitamin D. At least 1,500-2,000
IU/day of vitamin D may be needed to maintain blood level of vitamin D above
30 ng/ml; and
- Pregnant and lactating women require at least 600 IU/day of vitamin D
and at least 1,500 IU/day of vitamin D may be needed to maintain blood level
of vitamin D above 30 ng/ml.
Drs. Wagner, Taylor and Hollis, the ones doing many of the studies in lactating
and pregnant women, they recommend 25-50 IU per kilogram of body weight for
children 2-12 years. For those weighing more than 50 kg (110 pounds) then
2000-4000 IU is recommended. For pregnant women, they recommend 4000 IU.
For lactating women, they suggest 6400 IU a day.
And if it's sunny, and the right time of year, at the right latitude, go
outside and let Mother Nature take care of things, within reason. We don't need
sunburn- we just need a little sun. In my part of the world, that works about 3
months out of the year. And that may be generous. But boy, do we love it when
we can enjoy it!