Vitamin D, or calciferol, is a fat-soluble vitamin with a very well understood role in bone health. Over the last several years it’s role in immune function, cell growth, neuromuscular function and reduction of inflammation has prompted more routine testing of vitamin D levels.
Currently, there is intense interest in the role Vitamin D plays in pregnancy. A recent review article explored hundreds of studies on Vitamin D and pregnancy outcomes, and a number of important correlations are evident. It is clear that mother’s vitamin D status is associated with pregnancy outcomes and vitamin D supplements improve both the mother’s and the newborn’s vitamin D status.
Researchers are currently exploring the role that vitamin D plays in placental implantation, development of blood vessels, immune function, inflammatory response and blood sugar control in pregnancy. There is good evidence that low vitamin D levels in the mother may contribute to the following conditions in pregnancy:
- Preeclampsia (high blood pressure and other serious complications)
- Gestational diabetes
- Preterm birth
- Poor fetal growth
- Post partum depression
Vitamin D deficiency is common during pregnancy and varies by ethnicity and geographic location. One of the important sources of vitamin D is production in the body by the action of sunlight on the skin. Ultraviolet B energy converts 7-dehydrocholestrol to vitamin D3. This process is less efficient in darker pigmented skin, with use of sunscreen and in areas of minimal sunlight.
There are no established standards for optimal vitamin D levels in pregnant women, but many of the studies found correlations for poor outcomes with levels of 25-hydroxyvitamin D below 75 nmole/liter which is equivalent to about 30ng/ml. Most U.S. laboratories establish the normal range for 25(OH)D between 30 and 74 ng/ml.
So how can women of childbearing age optimize vitamin D levels before and during pregnancy? Foods that are rich in vitamin D include the fatty fishes such as salmon, trout, mackerel, tuna and eel. These are extra bonus foods because they are also high in the heart healthy omega-3 oils. Mushrooms that are grown in UV light have the ability to produce vitamin D3 just like the human body, “Doles” portabellos are an example of such a mushroom. Milk, some orange juice and many cereals are fortified with vitamin D3, but remember they are also high in sugar. Egg yolks, which are now considered healthy, are an excellent source of vitamin D. Beef liver and cod liver oil (yuck) are also good sources of vitamin D. Finally, vitamin D3 supplements are readily available and well tolerated.
Routine measurement of vitamin D levels in pregnancy is not currently the standard of practice. But given the many potential adverse outcomes that may be associated with deficiency of this vitamin, and the ease with which the deficiency can be corrected- perhaps it should be.