A breastfeeding mom who takes vitamin D supplements will pass along the benefits to her infant. (For Spectrum Health Beat)

If mom gets enough vitamin D during pregnancy, it’s helpful to baby.

We’ve long known this.

Vitamin D affects calcium absorption, cell growth, immunity and cell metabolism. It also crosses the placenta, which means mom’s intake level can make a difference to baby.

But to be perfectly honest, there are conflicting recommendations when it comes to pinning down a proper daily intake of vitamin D. And there is currently no universal recommendation on how much of this vitamin you need when pregnant.

Right off the bat, I’d encourage you to discuss your vitamin D level with your OB provider.

The Vitamin D Council recommends 4,000 to 6,000 IU daily, but the Endocrine Society recommends 1,500 to 2,000 IU per day. The Food and Nutrition Board sets it at just 600 IU.

A study by researchers in South Carolina found that a pregnant woman would need 4,000 IU of vitamin D each day to ensure her baby has enough at birth. Interestingly, the study also found that mothers who take 4,000 IU of vitamin D may experience fewer birth complications.

Another study found that a liter of breast milk from a mom who took 6,400 IU of vitamin D daily contained, on average, about 800 IUs of vitamin D. In moms who took 400 IU, a liter of breast milk contained about 50 IUs of the vitamin.

Clearly, mom can help baby if she supplements with vitamin D.

The ‘D’ test

Do you know your level of vitamin D? If not, you should ask to have it tested. It’s called a 25-hydroxy D test.

You should also seek to learn more about what your provider recommends for pregnancy, as far as supplementation and proper vitamin D levels.

Vitamin D is a fat-soluble vitamin, which means it is possible to ingest too much of it. It’s stored in fat. Water-soluble vitamins, on the other hand, are simply excreted if you take too much. (Vitamin C is an example of a water-soluble vitamin.)

Being overweight, spending a lot of time indoors, having dark skin and living in places where you don’t get a lot of sun in the winter predisposes you to a lower vitamin D level.

This is partly why you’ll see so many variations on the recommended daily intake of vitamin D. Where one person’s skin tone and lifestyle may create a need for more of the vitamin, another person’s attributes will call for less supplementation of the vitamin.

The American Academy of Pediatrics recommends children take 400 IU a day of vitamin D beginning in the first few days of life and continuing throughout child. This applies even during breastfeeding.

Why the recommendation into later childhood? Children are exposed to less sunlight these days, which can lead to the development of rickets, a softening of the bones.

Rickets had been nearly wiped out in the 19th century, so it’s not something people think children can develop in modern society.

But they can.

A 2014 study in England noted a fourfold increase of rickets since 2004. Another reason for the increase in rickets is that children aren’t playing outside quite as much—they spend more time inside with video games and technology.

One last note: If you’re wondering how to give vitamin D to your baby, it comes in a liquid form that can be spoon-fed.

Just keep in mind that the FDA has advised caution in administering the dosage—you absolutely must use a dropper of the proper size to provide the correct amount of vitamin D. And make sure to talk with your pediatrician first.