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Are You Getting Enough Vitamin D?
Known as the “sunshine vitamin,” vitamin D is produced in the body in response to the skin being exposed to sunlight. Considering the sun rises every day, most people must get plenty of vitamin D, right? Wrong. The Vitamin D Council says that approximately 1 billion people worldwide—nearly 15 percent of the world’s population—are vitamin D deficient or insufficient.
Vitamin D is important for a variety of functions in the body. Most noted is its role in bone health. Without adequate vitamin D, you only absorb a small amount of the calcium you consume. This can have negative, long-lasting effects on bone mineral density as you age, which in turn can increase your risk for stress fractures and other bone injuries. In addition, vitamin D plays a role in immune function, can reduce inflammation and might help decrease your risk for certain diseases like heart disease, hypertension, arthritis and certain cancers.
Emerging research also supports that vitamin D plays a role in athletic performance. Low vitamin D status may directly impair muscle strength and performance in athletes; however, more evidence is needed to understand the exact mechanisms.
What Leads To Deficiencies
Your exposure to sunlight is limited. If you run early in the morning or late in the evening, you might be at risk for vitamin D deficiency due to not being in the sun at the peak of the day. If you live above 37 degrees N latitude, little to no vitamin D can be produced by the skin in the winter months due to the sun’s position (the 37th parallel crosses through the middle of California, just north of the Texas panhandle and south of Virginia). In addition, those who wear clothing that covers most of their skin or put sunscreen on first thing in the morning might also be at risk.
You have dark skin. The pigment melanin reduces the skin’s ability to make vitamin D in response to exposure to sunlight. Thus, more time in the sunlight is required to activate vitamin D.
You have a high body fat percentage. Body fat takes up and stores newly synthesized vitamin D. People with a body mass index (BMI) greater than 30 often have lower blood levels of vitamin D.
Your liver or kidneys cannot convert vitamin D to the active form. As people age, their kidneys are less able to convert vitamin D to its active form. Therefore, individuals over 70 years old have increased needs.
You don’t consume vitamin D–rich foods. Vitamin D is only naturally occurring in a handful of foods such as fatty fish and their oils, beef liver and egg yolks. Cow’s milk is fortified with vitamin D, and certain brands of yogurt, cereals and orange juices are also fortified.
So, how do you know if you are deficient? The most accurate way to measure your vitamin D status is the 25-hydroxy vitamin D blood test. This can be requested at your doctor’s office.
The Institute of Medicine says that individuals ages 1 to 70 should consume 600 IU or 15 mcg of vitamin D per day. After age 70, the recommendation increases to 800 IU or 20 mcg (see chart).
How To Get Enough Vitamin D
Get some rays. Obtaining five to 30 minutes of sunlight a few days a week between 10 a.m. and 3 p.m. with your arms, legs and back exposed can help activate vitamin D in the body.
Consume vitamin D–rich foods. Adding cow’s milk, fatty fish, fish oil and other vitamin D–fortified foods to your diet on a regular basis can support your vitamin D needs.
Consider a supplement. Without enough sun exposure, regular consumption of vitamin D foods is not enough to maintain sufficient vitamin D status. So, if you are unable to be in the sun, you should talk to your doctor about taking a vitamin D supplement.
How To Tell If You’re Vitamin D Deficient
Amy Goodson, M.S., R.D., C.S.S.D., is a registered dietitian and consultant in the Dallas-Fort Worth area.