The role of vitamin D in bone metabolism has been known for a long time.
In recent years, there has been growing interest in vitamin D and breast milk among health professionals and scientists. This is mainly due to increasing rates of rickets in developed countries. To read more about rickets see our article: What Is Rickets? 5 Critical Symptoms
More recently, it has been discovered that vitamin D might have many other functions in the human body – such as cell growth and immune function – and that vitamin D could play an important role in the prevention of many chronic diseases.
Because vitamin D is so important, it’s essential – particularly for breastfed infants – to get enough of it, from birth.
Here are 7 facts you need to know about the role of vitamin D and breast milk.
#1. Breast milk is not deficient in vitamin D
Much of the literature written about infant vitamin D deficiency comments on the vitamin D insufficiency of breast milk.
It is not a coincidence that breast milk is the way it is. Breastfeeding is the biologically normal way to feed infants and the components of breast milk are designed to meet a baby’s needs. You can read more here; Breastfeeding 39 Days.
It’s true that levels of vitamin D are very low in breast milk, but it’s not a fault of nature; there are physiological reasons for it.
Why does breast milk have very low levels of vitamin D?
#2. We are designed to get vitamin D from sun exposure
When looking more deeply into why breast milk has very little vitamin D, we discover we’re meant to get vitamin D from sun exposure rather than from our diet. If we get sufficient vitamin D from sun exposure, then there is no need for breast milk to have much of it at all.
However, in countries like Australia, there are high rates of skin cancer. For that reason, most of us have taken notice of the public health messages about being ‘sun-smart’. This, combined with our technologically driven lifestyles, means many of us get less exposure to UV rays than previous generations did. Although spending less time in the sun is important in reducing the risk of skin cancer, it also reduces our vitamin D intake and increases our risk of vitamin D deficiency.
Human milk cannot be expected to supply breast fed infants with their entire vitamin D needs, because human beings are meant to make vitamin D from sun exposure. However, because we have reduced sun exposure (due to lifestyle or to minimise skin cancer risk), those at risk of vitamin D deficiency require supplementation.
But how much exposure to the sun is required to avoid vitamin D deficiency?
#3. Safe sun exposure time for children is unknown
Regular sunshine can help prevent infant vitamin D deficiency, but the safe exposure time for children is unknown.
The benefits of of exposing children to UV rays need to be weighed up against the risks. If you take your baby out in the sun, limited exposure in the early morning or evening might be best. The length of time needed to get enough vitamin D has not been accurately quantified and will vary, according to the time of day and where you live.
Sun Smart Australia provides information to help you determine how much sun is enough. You can visit their website to find out more.
#4. Not all babies are at risk of vitamin D deficiency
Not all babies are at risk of vitamin D deficiency.
Breastfed infants who are particularly at risk are those who:
- Are dark-skinned
- Receive too little sunlight (e.g. by living at higher latitudes)
- Are breastfed by mothers with vitamin D deficiency.
During pregnancy, a fetus lays down a store of vitamin D. The baby then uses this store during the first few months of life. If a baby is born to a vitamin D deficient mother, the baby’s own vitamin D status will be deficient at birth.
Women are often tested early in pregnancy to assess whether maternal vitamin D supplementation is necessary.
Formula fed infants do not require a vitamin D supplement as infant formula contains adequate vitamin D.
#5. The ideal vitamin D level is unknown
There is controversy about how much vitamin D is required for a lactating woman and a breastfed baby.
The National Institute of Health suggests vitamin D sufficiency is a blood concentration of at least 50 nmol/L. The Endocrine Society suggests vitamin D sufficiency is a blood concentration of at least 75 nmol/L.
Many other countries around the world, as well as some professional societies, have different guidelines for adequate vitamin D recommendations.
These differences are the result of an incomplete understanding of the biology and clinical implications of vitamin D, different purposes for the guidelines (e.g. for public health in a healthy population or for clinical practice) and/or the use in a randomized controlled trial to establish recommendations.
#6. Different countries have different recommendations
Depending on where you live in the world, the recommendation regarding vitamin D supplementation varies.
In the United States, for example, the American Academy of Pediatrics recommends 400 IU per day of vitamin D for all breastfed babies, from birth.
In Australia, the recommendation to use vitamin D supplements of 400 IU is limited to ‘at risk’ breastfed babies, such as those born to dark-skinned or veiled women.
#7. Vitamin D supplementation in lactating mothers improves vitamin D levels in breastfed infants
Research into maternal versus infant vitamin D supplementation shows that supplementing breastfeeding mothers can improve their babies’ vitamin D levels without direct infant supplementation. You can read more in our BellyBelly article, Breastfeeding mothers with influenza.
Breastfeeding mothers who take vitamin D supplements of 6400 IU will have adequate vitamin D in their breast milk to satisfy their breastfed babies’ requirement.
This offers an alternative to giving vitamin D drops directly to the baby.