Vitamin D Fact Sheet
Written by Editor   
Tuesday, August 05, 2014 12:36 PM

Imagine there were a nutrient that could protect your bones, brain and heart, and maybe even help you live longer. It's 100 percent free, and all you have to do to get it is go outside. Well, that nutrient exists -- it's vitamin D, which is created by our cells when our skin is exposed to sunlight. But despite these facts, many Americans aren't getting as much of the "sunshine vitamin" as they should. Here's what you need to know about vitamin D, and how inadequate levels can affect your health.

Vitamin D helps the body absorb calcium, which is vital for forming and maintaining strong bones and teeth. Research has also shown that vitamin D acts similarly to a hormone in the body and may play a role in regulating blood pressure, weight and mood. One recent study even suggests that having adequate levels can protect against early fatalities from conditions like cancer and heart disease.  When adults don't get enough vitamin D, they can suffer from osteomalacia (a softening of the bones), osteoporosis, bone pain or muscle weakness.

Vitamin D is also a key component in brain development, and a deficiency may contribute to low energy or depressive symptoms.

The body can make its own vitamin D, but only when skin is exposed to sunlight. For most people, spending just five to 30 minutes outside twice a week is enough for the body to synthesize healthy levels of vitamin D. 

Although most of our vitamin D comes from the sun, we can also get a substantial amount from food. Fatty fish and eggs contain vitamin D naturally, and many juices, dairy products and cereals are fortified with the vitamin, as well.  It's probably not possible to get the full, recommended amount of vitamin D -- 600 IU for adults up to age 70 -- from dietary sources alone.

A recent review published in the American College of Sports Medicine's Health & Fitness Journal concluded that people who are deficient in vitamin D may have compromised fitness levels. Studies have found, for example, that athletes could jump higher or sprint faster after they took supplements for several weeks or months.  But more is not always better, if you already have healthy levels of vitamin D, taking a supplement probably won't have an impact on your strength, speed or athleticism.

Extreme vitamin D deficiency -- defined as less than 12 nanograms of vitamin D per milliliter of blood -- is rare in the United States, but people who follow a strict vegan diet or have dairy allergies are at risk since they are not eating foods (like fish, eggs and milk) with naturally occurring or added vitamin D. Age and weight also play a factor in deficiency "As we get older and our kidneys become weaker, they may not be able to convert enough vitamin D into the active form that our bodies can use." Obesity can also lead to a deficiency, he adds, as the nutrient is leached out of the blood by body fat.

While most of us aren't dangerously low on vitamin D, we don't all have ideal levels, either. Current guidelines recommend that adults have at least 20 nanograms of vitamin D per milliliter of blood, says White, although 30 is an even better number for optimal bone and muscle health. Most Americans get close to meeting this guideline, but about two-thirds of us fall slightly short -- especially in the winter when we're not outside regularly.