Why are so many breastfeeding babies low on vitamin D?

Vitamin D, the “sunshine hormone,” is vital for bone health, and it might be important in other ways, too.

Recent studies suggest that newborns with poor vitamin D status suffer diminished immune function. Preliminary research has also linked vitamin D insufficiency with an increased risk of autoimmune disease, high blood pressure, and cancer. And as I’ve noted in a previous post, low levels of vitamin D may put kids at risk for early puberty.

So you want to make sure your baby is getting enough vitamin D. But is she? Based on the research I’ve seen, I wouldn’t bet on it. Especially if she is breastfed.

The trouble starts at birth. Studies of newborns in places as different as DenmarkIran, CaliforniaMassachusetts, and Southeastern China have reported that most babies were born with low levels of vitamin D.

In some cases, this meant that their vitamin D status — as measured by the prohormone “25[OH]D” in the blood — fell between 20 and 30 nanograms per milliliter (ng/mL), levels which are considered insufficient for optimal health, but not so low as to put babies at risk for bone diseases.

In other cases, however, these studies have reported more serious shortfalls. For instance, among babies born at an urban Massachusetts hospital, 58% had 25[OH]D levels less than 20 ng/mL, and 38% were “severely deficient,” with levels under 15 ng/mL. In the Chinese study, 91% of babies tested below 20 ng/mL.

Fast forward a few months, and it’s likely that many babies will have improved – if they’ve been getting vitamin-fortified baby formula. But exclusively breastfed babies tend to get stuck in the trouble zone. In a recent study of 4-month-old babies in New England, researchers concluded that “unsupplemented exclusively breastfed infants were at high risk of severe deficiency.”

Why? Babies get limited exposure to sunlight, and breast milk doesn’t have enough vitamin D in it. Not if the mother is herself insufficient, as many breastfeeding mothers are. And if you think your prenatal multivitamin is taking care of your needs, think again. Many such vitamins contain just 400 IU of vitamin D, an amount that may be inadequate for lactating women.

In the California study, 50% of new mothers who were taking 400 IU per day were nevertheless diagnosed with a vitamin D insufficiency. In another study, investigators monitoring vitamin D levels in both breastfeeding mothers and their infants reached this sobering conclusion:

“With limited sun exposure, an intake of 400 IU/day vitamin D(3) did not sustain circulating maternal 25(OH)D levels, and thus, supplied only extremely limited amounts of vitamin D to the nursing infant via breast milk.”

Happily, there is a simple solution: Get yourself and your baby tested.

Determining your blood levels of 25[OH]D is an important first step, because too much vitamin D is harmful. Once you’ve established the extent of your problem – assuming you have one – your physician can prescribe supplements. One option is for your baby to take these supplements himself. But you can also solve the problem by improving the vitamin D content of your milk. Recent research has shown that doctors can remedy vitamin D deficiency in nursing infants by supplementing mothers with temporary, therapeutic doses of vitamin D.

Given that so many women are themselves suffering from low levels of vitamin D, this approach seems like a no-brainer. But if you listen to the experiences of breastfeeding mothers–and read the published surveys–it’s astonishing how many families aren’t getting any sort of supplements at all.

Breastfeeding mothers: Did your doctor monitor your vitamin D status when you were pregnant? Has anybody suggested that you or your baby get tested now?

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6 thoughts on “Why are so many breastfeeding babies low on vitamin D?”

  1. I was told to give vitamin D for both of my kids. I just wish there was better choices, I told to use the enfimil brand which is(or was) sweetened and as dye in it.
    It is also tough to give drops to babies when they do not like what they are getting. My daughter hated it and would spit it out. When I went back to work and was pumping I would just mix it with a bottle and she would drink it but she was not a fan.
    We are so aware of the harmful effects of the sun we use sunblock which interferes with the absorption of vitamin D. We also live in VT where the sun is very weak in the winter, so even without sunblock the amount of Vitamin D you get is not very much.
    I worry some now as my kids drink raw milk so they do not even get vitamin D from their milk. I do give them vitamins but I wonder if it is enough.

  2. It’s not safe for babies to “get sun,” and as others have stated, virtually impossible anyway during winter months in certain climates (hello Midwestern USA!). Our doctor recommended vitamin D drops right from the get-go, it was very inexpensive and our newborn had no trouble swallowing a drop or two a day.

  3. If breast feeding is the super food for babies when why do we still have to supplemen with other vitamins? Don’t our bodies produce the nutrients our babies need? Breast feeding once was the sole sorce of food for babies since time began and now we are being told it’s not enough. Just like back in the 1950s “they” tried to tell mothers formula was better than breast milk.

  4. My daughtert’s pediatrician, who is also a lactation consultant, strongly supports breast feeding mothers taking vitamin D supplements. I tried giving my daughter vitamin D directly, and she hated it. And, “just getting more Sun” won’t work in middle to higher latitudes in winter.

  5. I live in Canada and I thought it was common practice for breast feeding babies to get vitamin d drops. Before I had my lo I bought the drops but didn’t need to use them when I had to formula feed.

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