Does breast milk contain enough vitamin D to prevent deficiency in breastfed babies?

Vitamin D is needed to build healthy bones and teeth in children, and is vital to prevent osteoporosis in adults.  It keeps you healthy in many others ways too: vitamin D helps prevent many cancers, hypertension, type diabetes 1, and is very important for good immune system.  Low vitamin D levels are connected with many autoimmune diseases like multiple sclerosis, Sjogren's Syndrome, rheumatoid arthritis, thyroiditis and Crohn's disease.

Breast milk tends to have very low levels of vitamin D, usually not enough to meet the needs of an exclusively breastfed baby.  American Academy of Pediatrics now recommends supplemental vitamin D for all breastfed babies.

The question that arises is how could breast milk be 'deficient' in vitamin D if it is supposed to be the perfect food for babies?  Is there a measuring error somewhere or what?

Some recent research is now shedding light on this question.  True, many many breastfed babies are deficient in vitamin D, and true, their mother's milk does not have enough.  But this seems not to be the fault of breast milk per se, but instead is caused by the mother not having sufficient levels of vitamin D.  In other words, moms are deficient too, and that is why breast milk has low levels of vitamin D!

Hollis and Wagner conducted a study where lactating mothers were supplemented with either 2,000 or 4,000 IU of vitamin D daily.  The idea was to see if that fixes the baby's vitamin D levels as normal.  In both groups, the vitamin D status of the infant improved greatly (as did the mother's).  In the 4000 IU/day group, the infants' D-vitamin levels normalized after 3 months of breastfeeding.[1]  Note that 4,000 IU a day is ten times the current (woeful) recommended intake for vitamin D (which is 400 IU for adults) by the Food and Nutrition Board!

In another, earlier study from Finland, researchers supplemented mothers with either 1,000 IU or 2,000 IU of vitamin D daily.  They found that 1,000 IU was NOT enough to make any significant changes in vitamin D content of breast milk, but 2,000 IU was sufficient so the infants had normal levels of vitamin D.[2]

There is other evidence too about the fact that normal adults actually need 3,000 - 4,000 IU of vitamin D daily.  Another recent study examined how much vitamin D normal healthy males actually use daily.  The answer was around 3000-5000 IU cholecalciferol (the natural form of vitamin D) per each day.  The study was conducted over winter months, and it seemed that those men got more than 80% of their winter vitamin D need from stores their body had made during the summer months when they were exposed to sunlight.[3]

The recommendation of 400 IU daily for adults is not based on how much of vitamin D you really need for optimal health, nor on the actual levels of vitamin D in bloodstream.  It has been based on the amount of vitamin D in one teaspoon of cod liver oil, as that kept children from getting rickets.[1]  But, up until recently, no one really knew how much adults or pregnant/breastfeeding moms would optimally need.

Vitamin D deficiency is getting to be more and more widespread as people are avoiding sunlight. Simple sun exposure is obviously a way for children to get vitamin D, and of course, you can help your baby to get vitamin D by letting her get some sun, just be extremely careful so she won't burn.  But it is nice to know from this recent study that breast milk can provide all vitamin D for the infant, say, during winter time, if the mother herself has sufficient stores of vitamin D.

Sources of vitamin D

The best source of vitamin D is sunlight, because your skin makes vitamin D from being exposed to the ultraviolet rays in sunlight.  You cannot overdose because if you stay in the sun long enough, the sunlight actually destroys any excess vitamin D made in the skin.  Sunscreen and glass windows will block that from happening, however.  Indeed, as people have started to fear sunlight because of skin cancer threat, deficiency of vitamin D has become extremely widespread in Australia, in United States, in Europe and other parts of the world - and this includes most pregnant and lactating mothers.

Most foods don't contain vitamin D in any great amounts.  You can get some vitamin D from cod liver oil, fish, and fortified dairy products.

If you can't get enough sun, then vitamin D supplements can be the answer. If you think you need to rely mostly on supplements, it is advisable to have a doctor test the level of vitamin D in your blood so you will not overdose.

How much vitamin D do you get from sunlight?

First, no matter what, do not burn yourself!  You need to start with small amounts and increase your sunlight exposure carefully till you have a base tan.  Some individuals don't tan well because of their skin type and they need to be extremely careful.  Fortunately, the maximum production of vitamin D in the skin occurs before skin would turn red/pink (which is a sign of slight burning).

With the whole body exposure (naked), adults can produce typically 20,000-30,000 IU of vitamin D in response to bright summer sunlight in a single sunbathing session.  For each 5 percent of body surface exposed, the skin can make about 100-200 IU.

The amount of time depends mainly on how white your skin is, and how intense the UV-B rays happen to be.  With totally white skin, 10-20 minutes would be enough - but before the skin turns pink.  Black skin has an in-built sunblock, so black individuals need 120 minutes for this kind of vitamin D production.  Varying levels of tanned/pigmented skin would need something between those amounts.

When the sun is at a low angle on the sky, the intensity of UV-B rays is greatly reduced.  That is why early morning, late afternoon, or winter sun can be too weak to provide optimum levels of vitamin D.  In much of the US, which is between 30 and 45 latitude, six months or more during each year have insufficient UV-B sunlight to produce optimal D levels.

Your body stores vitamin D.  So if you get enough sun exposure during the summer months, you may have enough for the winter too, but most people in United States would benefit from supplemental vitamin D during winter.

What about skin cancer and sunlight?

True, sun exposure is associated with higher skin cancer risk, and people who don't tan well are especially at risk and need to be very careful.  But the picture is not so simple as people are led to believe.  Consider these facts:

• melanoma, the deadliest and most dangerous form of skin cancer, is connected with intermittent, occasional, sun exposure;
• chronic or constant sun exposure actually reduces risk of melanoma;
• there is good evidence that having a right ratio of omega-6 fats versus omega-3 fats in person's diet is a factor in preventing melanoma;
• non-melanoma skin cancers are associated with accumulated sunlight exposure but are about 95% treatable;
• antioxidants applied topically and from diet/orally can greatly diminish the damage that UV light does to the skin;
• sunlight actually helps to prevent most other cancers, especially breast, prostate and colon cancers;
• Sunlight is useful in preventing/treating multiple sclerosis, depression, seasonal affected disorder, psoriasis and tuberculosis.

As with everything, there can be a healthy balance when it comes to sunbathing.

Sources & resources