The Importance of Vitamin D

Vitamin D plays an important part in maintaining general health. It helps the body build strong bones by aiding calcium absorption, boosts the immune system and helps the body regulate moods. Lack of this vitamin is part of the reason many people experience "the blues" this time of year and can result in stunted bone growth and malformation in children (rickets), and osteomalacia  if prolonged. Lack of vitamin D also contributes to a lower immune system, causing you to get sick more frequently, especially during the winter. 

People who live in Northern Climates or regions where sunlight is shorter during one half of the year are particularly prone to Vitamin D deficiency. Others, such as people with inflammatory bowel syndromes, dark skin, a vegan or ovo-vegetarian diet,  breastfed infants and people who have undergone gastric bypass surgery are also at higher risk. 

Vitamin D is obtained in two ways. The first, best way to get it is with direct sunlight each day. You don't have to get the sun all at once either, so if time or weather conditions are an issue, try being outdoors in small increments. Alternatively, sit in front of a sunny window while working or watching TV. Sun Lamps are becoming popular. The light in these mimic natural sunlight and do provide some Vitamin D. For people living in Norther Climates, winter sunlight is not strong enough to produce Vitamin D that can be absorbed by the skin.The only other way to get this important vitamin is through some foods or vitamin supplements. Unfortunately, foods that contain Vitamin D are extremely limited. Salmon, Tuna, cod liver oil and egg yolks are the best sources. Other foods such as milk, yogurt, some cheeses and orange juice contain vitamin D that has been added artificially. A few mushrooms may contain Vitamin D as well. 

Vitamin D supplements are available and come in two forms: Vitamin D2 and Vitamin D3. Though they are manufactured somewhat differently, the only difference between them is that at higher doses, Vitamin D2 is somewhat less potent. The recommended daily allowances for Vitamin D intake are : Children less than 1 year: 400 IU.  Persons over one year old: 600 IU. There has been some speculation that 600 IU are not sufficient, especially for people living in Northern climates. For those folks, 2,000 IU  is the recommendation in the winter in addition to daily sunshine in the summer months. 

If you're not sure whether you're getting enough Vitamin D, there is a blood test available to check your levels. It's called the  25-hydroxy vitamin D blood test. It's a good idea to ask your doctor for this simple test periodically, especially if you are at risk for vitamin D deficiency. Levels between 20 and 50 nanograms/millileter are considered adequate while levels below 12 ng/ml indicates deficiency.

Whenever possible, spend time, especially with your children, outdoors. Remember that too much time in the sun can cause burns and potentially lead to certain types of skin cancer, so moderate your time wisely.

Until next time, 

Be well!

Sources: 

1. Holick MF. Vitamin D. In: Shils ME, Shike M, Ross AC, Caballero B, Cousins RJ, eds. Modern Nutrition in Health and Disease, 10th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.
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3. National Institute of Standards and Technology. NIST releases vitamin D standard reference material, 2009.
4. Holick MF. Vitamin D: the underappreciated D-lightful hormone that is important for skeletal and cellular health. Curr Opin Endocrinol Diabetes 2002;9:87-98.
5. Webb AR, Kline L, Holick MF. Influence of season and latitude on the cutaneous synthesis of vitamin D3: Exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. J Clin Endocrinol Metab 1988;67:373-8. [PubMed abstract]
6. Vieth R, Bischoff-Ferrari H, Boucher BJ, Dawson-Hughes B, Garland CF, Heaney RP, et al. The urgent need to recommend an intake of vitamin D that is effective. Am J Clin Nutr 2007;85:649-50. [PubMed abstract]
7. National Institutes of Health Osteoporosis and Related Bone Diseases National Research Center.Osteoporosis overview. October 2010.
8. Vitamin D Council. Vitamin D and Depression: A patient friendly summary. www.vitamindcouncil.org/health-conditions/depression/,2012.