41 Percent of U.S. Adults Deficient in Vitamin D: Vitamin D Supplements Can Fill in the Gaps

by Timothy R. April 18, 2014

41% of U.S. Adults Deficient in Vitamin D: Vitamin D Supplements Can Fill in the GapsThere is no doubt that we need adequate vitamin D to maintain good health, and for most people, getting enough might not be as simple as getting a little sun. Few natural food sources contain vitamin D, and for some people, supplementation is necessary to fill in gaps and support this vitamin’s important functions in the body.

Among the important roles that vitamin D plays in our body is calcium absorption. Sufficient vitamin D levels in the blood have been associated with prevention of osteoporosis for those at risk, such as older adults, post-menopausal women, those who take chronic steroids, and individuals who are unable to exercise.1 Experts are now researching the effects vitamin D may have in the body related to immune function, nerve function, and even cancer and cardiovascular disease.2

Vitamin D is a good example of a vitamin that may be very difficult for some people to obtain through diet alone in adequate amounts. The best natural food sources of vitamin D are liver, fatty fish, egg yolks, and mushrooms, but most people get the bulk of their vitamin D from fortified milk, orange juice, and breakfast cereals.1 Vitamin D is a unique vitamin in that it can also function as a hormone, which we produce when our skin is exposed to direct sunlight. If you live in a geographical area where most days are sunny, that method might be convenient, but many people do not have the opportunity to follow the recommendation of experts to sit in the sun for approximately five to 30 minutes a day—twice a week between 10 a.m. and 3 p.m.—for adequate vitamin D production. Unprotected sun exposure can also increase the risk of developing skin cancer, and many people have been advised to wear sunscreen daily by their physician or dermatologist.1 Sunscreen can limit the amount of vitamin D produced.

Vitamin DThe Required Daily Allowance (RDA) for vitamin D is based on age. Infants from birth up to one year of age should take in 400 international units (IUs) a day; people ages one to 70 should take in 600 IUs daily; and adults over 70 years old need 800 IUs each day. This value was developed based on minimal sun exposure in order to be appropriate for most people.1 The only way to tell if you have adequate serum levels of vitamin D in your blood is with a blood test. Blood serum levels of 25-Dihydroxyvitamin-D between 50 and 125 nanomoles-per-liter (nmol/L) are generally considered adequate without being excessive in healthy individuals.1

Vitamin DMany individuals are at increased risk of deficiency. Infants who are exclusively breastfed need supplements of 400 IUs of vitamin D daily, as human milk does not contain adequate vitamin D amounts. Aging often results in deficiency since older people may be eating less and have a decreased ability to make vitamin D from sunlight. People with darker skin naturally have higher levels of melanin, which reduces the skin’s ability to synthesize vitamin D. Many health conditions, such as Crohn’s disease, liver disease, bariatric surgery, cystic fibrosis, and celiac disease, can impair the absorption of fat—and as a fat-soluble compound, vitamin D relies on intestinal fat absorption to enter the bloodstream. New research is also suggesting that obese individuals may have lower average vitamin D levels in their blood, as fat tissue under the skin may impair production of vitamin D from the sun. Strict vegetarians who do not consume milk or other animal products may also be at risk of too-low vitamin D levels due to insufficient consumption of natural or fortified vitamin D-containing foods.1

Vitamin D has been proven to be essential to human health. Because of the large number of people who are deficient or at higher risk for becoming deficient, and the difficulty in obtaining sufficient amounts, vitamin D supplements are widely available in supermarkets, drugstores and pharmacies. People can find good supplement choices among the varieties of different forms of vitamin D available, from liquid drops and gummies to capsule forms.

These statements have not been evaluated by the Food and Drug Administration. Products listed are not intended to diagnose, treat, cure, or prevent any disease.

JodiAuthor: Jodi Schweiger RD, LD, CDE
Diabetes Program Coordinator, Hy-Vee

Jodi Schweiger RD, LD, CDE, received a Bachelor of Science degree from Iowa State University and completed a dietetic internship program at Iowa State University. Jodi is a Certified Diabetes Educator and a health coach. She is a current member of AADE and also is serving as President of Iowa American Association of Diabetes Educators. Jodi has 11 years of experience as a Hy-Vee dietitian and her specialties include diabetes, weight loss, hyperlipidemia, hypertension, basic nutrition counseling and corporate health and wellness.


  1. Vitamin D: Fact Sheet for Health Professionals. National Institutes of Health Office of Dietary Supplements Website. http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/. Reviewed 6/2011. Accessed 3/2014.
  2. Wang TJ, Pencina M, Booth S, et al. Vitamin D Deficiency and Risk of Cardiovascular Disease. J Am Heart Assoc. 2008; 117:503-522. doi: 10.1161/ CIRCULATIONAHA.107.706127.
  3. Forrest KY, Stuhldreher WL. Prevalence and correlates of vitamin D deficiency in US adults. Nutr Res. 2011; Jan;31(1):48-54. Doi: 10.1016/j.nutres.2010.12.001.

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