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United States Department of Agriculture

Agricultural Research Service

Vitamin D: What is enough?
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By Cindy Anderson

It seems that news about the health benefits of vitamin D is reported daily. Studies are reporting that vitamin D reduces the risk of heart disease, diabetes, rheumatoid arthritis, multiple sclerosis and osteoporosis, to name just a few.

So what is the problem? It seems that many of us just don’t have enough vitamin D in our systems, putting us at risk for a wide variety of health problems.

If vitamin D is so important, why is it so hard to get enough? Our main sources of vitamin D are supplemented foods and sunshine, which is why vitamin D is also known as the “sunshine vitamin”. When the skin is exposed to the sun, our bodies are able to produce vitamin D, which then travels to the sites in the body where it can be used.

For those of us who live in the northern latitudes, we know all too well that there is just not enough sunshine throughout the year. In the winter, even when we do have a chance to let our skin see the light of day, the rays of the sun aren’t strong enough to be very effective in making vitamin D. In the summer, our concerns about skin cancer have led to less sun exposure and more sunscreen use, also limiting our ability to produce vitamin D.

In order to get enough vitamin D in our diets, we need to eat foods that have been supplemented with vitamin D as there are few foods that naturally contain this important vitamin. Choosing foods fortified with vitamin D is becoming much easier as the number of supplemented foods available seems to increase along with our knowledge of the health benefits of vitamin D.

Important sources of vitamin D include milk, certain types of yogurt and juice, fortified cereals and breakfast bars. It is important to read the nutritional labels on food products to be sure there is vitamin D added.

But even with the increased availability of vitamin D-containing foods, many people living in the northern Plains are likely to have insufficient levels of vitamin D in their bodies. This leads us to the question of “how much is enough vitamin D?”

The current recommendation of the U.S. Food and Nutrition Board is for most people to consume 400 international units of vitamin D daily. Recently, this has been questioned, as many experts believe that a much higher amount is needed to get the greatest health protective effects.

Certain groups of people may need even more vitamin D than others, including pregnant women. Vitamin D is especially important during pregnancy, as the mother must meet her own needs for vitamin D and those of her developing baby. Also, the placenta (the organ that provides oxygen and nutrients to the growing baby) needs vitamin D for its own development. If there is not enough vitamin D for the correct development of the placenta and its blood vessels, this can present a nutritional challenge for the baby. It also can present a risk to the mother, as improper blood vessel development can lead to a condition called pre-eclampsia, a form of hypertension in pregnancy. Pre-eclampsia is a serious pregnancy complication, which can cause babies to be born small. Pre-eclampsia also is linked to future development of hypertension in mothers and their children later in life.

Many studies have shown that insufficient levels of vitamin D increases the risk of pre-eclampsia and future cardiovascular disease, though little is known about vitamin D status and the risk of pre-eclampsia in women living in the northern Plains. Because vitamin D levels can change depending on the season, it is important to determine the effects of different levels of vitamin D at different times during pregnancy.

UND and health care partners are conducting a study at the Grand Forks Human Nutrition Research Center that will determine vitamin D status in pregnant women and the link with markers of placental blood vessel development and health risks.


Last Modified: 12/8/2008
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