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Why is vitamin D so critical for good health?

Nutritionist, WebMD Medical Expert
University of Maryland

The National Institutes of Health set the recommended daily allowance (RDA) of vitamin D at 600 IU for people over age 18 and 800 IU for people over age 70, as did the Institute of Medicine (IOM) in 2010. Frankly, many doctors and scientists feel that the recommendations are too low. 

Vitamin D is one of the fat-soluble vitamins (e.g. A, D, E, K). Make sure to eat some fat-containing food (e.g. nuts, low-fat dairy) for optimal absorption. There are two main forms of the vitamin: D2 (ergocalciferol) and D3 (cholecalciferol). Catching ultraviolet B rays will increase your D3 levels. Fatty fish, mushrooms, eggs and meat are rich in D, as well as foods specifically fortified with D. Vitamin D is essential for the proper absorption of calcium and phosphate. That’s why vitamin D is so critical for bone health.

What you may not know is that recent research has also shown that adequate vitamin D levels are necessary for optimal immune, brain, nerve, and muscular function and control of genes that can influence our tendency toward certain diseases. Research in these areas is still evolving.

How does someone become vitamin D-deficient? Remember the age-old recommendation to get your 15 minutes of daily sunshine? Well, as it turns out, that may not be enough. A study of young Hawaiian skateboarders and surfers found that over 50% of them had vitamin D levels lower than average. Slathering on sunscreen could be an issue in blocking adequate absorption. What was really interesting was that the vitamin D levels of these tropical sun-bathing folks were compared to levels among Wisconsin residents who were taking vitamin D supplements. Guess who had better levels? Yep, it was the pale-skinned Midwesterners. Apparently, outdoor training and recreation wasn’t cutting it for maintaining adequate vitamin D levels. 

What should your vitamin D level be? Here’s the rub. The IOM panel recommends 20 ng/mL as a sufficient level, while some vitamin D advocates, including the Endocrine Society and the International Osteoporosis Foundation, note that 30 ng/mL is necessary for optimal bone health. Can you have too much? Evidence suggests that levels above 50 ng/mL may pose an increased cancer risk. But that’s not the problem for most of the population. Not having enough D on board is the critical issue.

The good news is that emerging information about vitamin D’s potential has prompted excellent new research studies. For instance, the National Institutes of Health has initiated a study to include 20,000 men and women over age 60 to study whether 2,000 IU of vitamin D, omega-3 fatty acids from fish oil, or placebo will lower the risk of heart disease. Stay tuned!

Meanwhile, what should you do?

   1. Get your vitamin D level checked. This is especially important for those people who are getting little sun, are at risk for osteoporosis, may have inadequate dietary intake, and are either taking no vitamin supplements or are taking them sporadically. It’s just good to get a baseline. Knowledge is power.

   2. Discuss your vitamin D status and supplements with your medical team. Because there is controversy surrounding the IOM report regarding what is a normal D level and supplement intake, you need to talk with your medical professional about your individual situation. Your gender, age, level of physical activity, nutrition intake, bone status, osteoporosis risk, and sun exposure are all factors that must be considered. Then add to this your D level and you can have a comprehensive discussion about next steps to optimize your D status.

   3. Add up your daily D. Just for grins, whip out your supplements and add up how much D you’re actually consuming. Multivitamins contain D at varying levels, while calcium supplements are usually fortified with D. Check out how much D you’re consuming from foods sources, including fortified dairy and cereals. This will help you monitor your total intake. And it will be helpful to share this information with your medical team when you’re deciding how much D you need on a daily basis.

   4. Soak up a few rays. Even though we now know that 15 minutes in the sun is probably not enough to bump your D levels sky high, it’s still good to get outdoors to reap whatever benefit you can from the sun, as well as enjoy your external environment while staying physically active. Just remember to smooth on that sunscreen after 15 minutes of exposure or you’ll never hear the end of it from your dermatologist.

   5. Eat D-licious foods. You saw the laundry list of natural food sources for vitamin D. If you eat salmon, try to get the wild (not farmed) type, as it has fewer contaminants. I’m increasing my egg consumption and integrating more mushrooms into my daily salads and side dishes.

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