Vitamin D:  Why we need it and how we get it by Lakeshore Medical Breastfeeding Medicine Clinic


This is one of my favorite topics because there are so few times that I read research and I go "of course that's the answer.”  Too much of what research is about leads just to further questions, which is great- we should always be in pursuit of new knowledge.  But sometimes it’s nice just to have something “click” and feel like why on earth didn’t we think of this before? 


A few caveats before we start.  I am writing from Franklin, a lovely suburb of Milwaukee, Wisconsin in the United States.  Wisconsin is known for cows, cheese and great football.  In fact, Wisconsin’s Green Bay Packers famously play on “The Frozen Tundra.”  We don’t get a lot of useful sunshine where I am.  I got in a lovely discussion about the necessity of vitamin D supplementation with a reader when I realized that her words were spelled funny- like “coloured."  She was in New Zealand.  New Zealand is not known for its Frozen Tundra. So I’m writing primarily for those of you living north of Atlanta, the area most at risk for being deficient in Vitamin D.


My experience with vitamin D had been “it’s fat soluble, don’t take too much” and “strong bones and teeth.”  Then, the American Academy of Pediatrics recommended that breastfed infants receive supplementary vitamin D. Those recommendations have changed over time to include all children, regardless of mode of feeding, but at the time I was like “what?” and decided to ignore it.  How could anything be wrong with breastmilk and why just pick on the breastfed population?  As if we didn’t have enough obstacles to hurdle to get mothers to breastfeed- now we have this assertion that it’s deficient in vitamin D? Phooey.


Yes, I was wrong.  I did my homework, read the research, and there’s just too much of it to ignore now.  We are, in my part of the world, all likely to be insufficient in vitamin D. And for infants, the mode of feeding doesn't matter.  All children need at least 400 IU from the first few days of life onwards.  For a child feeding formula, that would take 34 ounces a day to get.  It isn't just a breastfed infant issue. (It didn’t hurt my acceptance of these recommendations, I admit, when  we found out that it was a population problem and not just one where we pick on breastmilk or infants.) 


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. There is more research about how important Vitamin D is to the immune system than about Vitamin C, zinc or echinacea.   Research tell us 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!


Of course, one size does not fit all. Talk to your doc about your circumstances, latitude and potential risk for vitamin D insufficiency, or consider getting your levels of 25 hydroxy vitamin D {25(OH) D} checked to help with a dose that’ll be good for you, and your kids.  And have fun watching as the new research keeps coming.


The sun has a purpose.  Who knew? 


 Jenny Thomas, MD, MPH, IBCLC, FAAP, FABM

interested in more?