Vitamin D has increasingly become part of the blood work accompanying a physical at the doctor’s office. This may be for good reason, as many people are falling short on this important vitamin.
Vitamin D is a fat soluble vitamin that is essential for proper functioning of many organ systems. It has two forms in fortified foods and supplements called vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Besides food and supplements, vitamin D can be produced in our skin by exposure to ultraviolent sunlight. With our ever-increasing use of sunscreens and avoidance of the sun’s harmful rays, certain populations of people may be deficient in this vitamin if not taking steps to get adequate amounts in food and supplements.
The classical diseases associated with vitamin D deficiency are Rickets and Osteomalacia. Rickets is a disease of childhood characterized by a failure of bone to mineralize properly resulting in soft bones and skeletal deformities. In adults, osteomalacia causes bones to weaken and symptoms of bone pain and muscle weakness often accompany, but may also be subtle in early stages.
Obtaining appropriate intakes of Vitamin D can be difficult to achieve, especially for non-milk drinkers. Vitamin D is found in limited foods naturally, so most Vitamin D in Americans’ diets is provided by fortified foods. The U.S. milk supply has voluntarily fortified milk. Other products that may be fortified include cereal, yogurt, and orange juice. Some foods with naturally occurring Vitamin D include cod liver oil, salmon, trout, egg yolk, liver, sardines, canned tuna, and cheese.
People who limit their exposure to the sun, women who wear head coverings and robes, or those who spend limited amounts of time outside are at risk.
So, who is at risk? Breastfeeding infants receive the best nutrition available from nursing, but their vitamin D requirements cannot usually be met by human milk alone. The American Academy of Pediatrics recommends that exclusively and partially fed breastfed infants be supplemented with 400 IU of vitamin D daily until weaned and consume >= 1000 mL/day of fortified infant formula or cow’s milk. People who limit their exposure to the sun, women who wear head coverings and robes, or those who spend limited amounts of time outside are at risk. People with darker skin due to the larger amounts of melanin reduce the ability to produce vitamin D from sunlight. The elderly cannot synthesize vitamin D as efficiently as in their younger years, and they are also more likely to spend less time outdoors. Those who have undergone gastric bypass surgery will also be at risk for vitamin D deficiency secondary to malabsorption since part of the small intestine where vitamin D is absorbed has been bypassed.
What other long-term health risks are associated with low levels of vitamin D? Osteoporosis is more often associated with lack of calcium, but insufficient vitamin D reduces calcium absorption. Having adequate levels of this vitamin along with calcium may reduce the risk of osteoporosis. There is some evidence that certain types of cancer such as colo-rectal, prostate and breast cancers may be influenced by deficiencies, but more research is needed. Vitamin D deficiency has also gained interest in those involved in cardiovascular disease research. Evidence is limited, but growing, linking it to several cardiovascular risk factors including stroke, heart attack, and peripheral artery disease.
So, how much vitamin D do we need a day? The Recommended Dietary Allowance (RDA) is the average daily level of intake sufficient to meet the nutrient requirements of nearly all healthy people. Both males and females from 0-12 months should get 400 IU per day, 1- 70years old 600 IU per day, and over 70 years should get 800 IU per day.
The next time you are in for your annual physical, it may not be a bad idea to ask your doctor if they think it is appropriate to check your vitamin D level. In the meantime, make sure you are getting enough dairy, especially from skim milk, and consider a multi-vitamin and/or a calcium supplement with vitamin D. A registered dietitian can help you too!
About the Expert: Jennifer Paschaloudis, MS, RD.