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United States Department of Agriculture

Agricultural Research Service

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A D-Lightful Vitamin
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Cindy Anderson, Ph.D.

It has long been known that vitamin D is necessary for strong bones and teeth, but its health benefits also include lower risks for heart disease, diabetes, rheumatoid arthritis and multiple sclerosis.  These effects involve its essential roles in calcium absorption, bone metabolism and the expression of many genes-and most people don't get enough of this important vitamin. 

Vitamin D is different from most other vitamins in that it can be made by the action of sunlight on the skin, hence, its name as the "sunshine vitamin". In order to make enough vitamin D, one must get sufficient sun exposure directly on the skin.  In North Dakota, this means the middle of the day and only in the summer months.  A study at the USDA Grand Forks Human Nutrition Center showed that, even in midsummer, the solar exposure is sufficient to produce significant amounts of vitamin D only between the hours of 10 am and 4 pm.  Even then, our indoor lifestyles, as well as the use of long sleeved clothing and sunscreens, effectively limit our capacity to make vitamin D.  Accordingly, people living north of Atlanta, Georgia show seasonal variations in their blood vitamin D levels, with the highest levels in the summer and lower levels through the rest of the year. The difference in vitamin D levels mean that most people don't have sufficient levels of vitamin D in their bodies they need throughout the year. So, no matter where people live, most need extra sources of vitamin D to assure adequate amounts to meet their daily needs.

Very few foods in nature contain vitamin D, but some are "fortified" with the vitamin. The amount of vitamin D that can be added in fortified American foods is regulated by the U.S. Food and Drug Administration. For example, milk actually contains very little vitamin D, but is usually supplemented with vitamin D3 for U.S. retail sales. In addition to milk, important sources of vitamin D include certain types of yogurt and fruit juices, fortified cereals and breakfast bars. In order to know how much vitamin D is in your food, read the nutritional label.  It will tell you how much vitamin D you are getting in that food.  Many people also choose over-the-counter dietary supplements containing vitamin D.

The biggest question most people have is, "How much vitamin D should I take?" Most people aged 1 to 70 years, are recommended to consume 600 international units (IU) of vitamin D per day. For people over 70 years, 800 IU per day is recommended that's because the ability to produce vitamin D in skin declines with age.  For infants in the first year of life, the recommendation is a daily intake of 400 IU. Intakes up to 4000 IU per day are regarded as safe for children and adults aged 9 to 70 years.

Vitamin D is especially important during pregnancy, as the mother must meet her own needs for vitamin D as well as those of her developing baby and the placenta which provides oxygen and other nutrients to the growing baby. Insufficient vitamin D impairs the development of the placenta and its blood vessels. That can present a nutritional challenge for the baby an increase the mother's risk of preeclampsia, a form of high blood pressure in pregnancy. Preeclampsia is a serious pregnancy related complication, which can cause babies to be born small and increase the risk of future development of high blood pressure in both the mother and child.

Adequate vitamin D also is especially important for breastfeeding mothers. The vitamin D content of breast milk reflects the vitamin D status of the mother. If a mother's breast milk has inadequate vitamin D she may not provide sufficient amounts to meet her infant's needs. Vitamin D is important to overall health and wellness no matter how old you are. Be sure to get enough, so you can get the benefits of this "D"-lightful vitamin.

You can learn more about vitamin D and other healthful components of foods at the website: Be sure to check out the free "Interactive Tools".

Last Modified: 8/13/2016
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