How to Know if You're Deficient in Vitamin D

David Juan, MD

Vitamin D is one of the most important nutrients to ensure you get enough of every day. While there are many essential nutrients (all available as natural supplements), few have the disease-preventing power of vitamin D. It is important to know if you are getting enough vitamin D. For that, you must know two main things. The first is who is at greatest risk for a deficiency. The second consists of the signs and symptoms of being deficient.

The blood level of 25 hydroxyvitamin D determines if you are vitamin-D sufficient, insufficient or deficient. Here's how it breaks down:
-- Below 20 ng/mL = deficient
-- 20-32 ng/mL = insufficient
-- 32-100 ng/mL = sufficient

Since the main roles of vitamin D in your body are to absorb calcium and help control neuromuscular functions, the optimal levels need to be around 87 ng/mL for these vital functions to occur. A recent survey shows that vitamin-D insufficiency in the U.S. was on the rise from 1988 to 2004. During this period, the prevalence of having levels under 10 ng/mL (vitamin-D deficient) rose two to six percent. Those who were vitamin-D sufficient, meanwhile, dropped from 45% to 23%. In a UK study, more than 50% of the adult population was found to have vitamin-D insufficiency and 16% to have deficiency.

Those are big percentages. Who is at the greatest risk of vitamin-D deficiency or insufficiency? The major risk factors include the following:
-- Inadequate exposure to the sun
-- Having dark-colored skin
-- Aging with decreased ability to make vitamin D from the skin and kidney
-- Inadequate intake of vitamin-D-rich foods
-- Being obese
-- Infants who are breast-fed exclusively
-- Being pregnant, as more vitamin D is needed for health of mother and fetus
-- Fat malabsorption syndromes such as cystic fibrosis and cholestatic liver disease
-- Inflammatory bowel disease such as Crohn's disease with impaired vitamin-D absorption
-- Drugs that impair vitamin D metabolism or absorption
-- Overuse of sunscreen covering every part of exposed skin.

For adults, here are the signs of being vitamin-D deficient or insufficient. Read them carefully and, if you have any doubts, see your doctor.
-- Pain (foot, thigh, pelvis, hip, rib)
-- Muscle weakness
-- Muscle aches in limbs and back
-- Low bone density or other bone-related issues (suggesting poor calcium absorption)

Source:
1. Ginde, A.A., et al., "Demographic Differences and Trends of Vitamin D Insufficiency in the US Population, 1988- 2004," Archives of Internal. Medicine, 2009; 169: 626-32.
2. Hypponen, E., et al., "Hypovitaminosis D in British adults at age 45: nationwide cohort study of dietary and lifestyle predictors," American Jounal of Clinical Nutrition, 2007; 85: 860-8.

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