Dr. Russell Greenfield: Experts believe that up to half of Americans, including children are low in vitamin D. Vitamin D helps maintain strong bones, but it also regulates over 200 genes with actions throughout the entire body. Vitamin D may help protect against high blood pressure, multiple sclerosis, diabetes and heart disease.

Adequate vitamin D levels may also help protect against certain forms of cancer including colon cancer, perhaps even breast and prostate cancer.

So what does this mean for you? It likely means that you could benefit from supplemental vitamin D, along the lines of at least a thousand IU or International Units per day. But the best way to know for sure is a visit to your doctor, to get a blood test for what's called a 25-hydroxy vitamin D level. People with dark skin, those who stay endorsed particularly the elderly, those living in colder climates, and overweight individuals are especially at risk for low vitamin D levels.

Breastfed babies are also at risk, so moms need to be sure they have adequate vitamin D levels too. Exposing the skin to sunlight for a 15-20 minutes a day, produces enough vitamin D for some people to be well. In addition, concerns about skin cancer are very real.

So after getting your few minutes in the sun, be sure to head back in doors to apply sunscreen and cover up well before going outside again.

Some foods provide vitamin D, most notably oily fish such as wild salmon, unless you are eating oily fish everyday however, the amounts found in foods are not sufficient alone to maintain healthy vitamin D levels.

Now Vitamin D supplements typically come in two forms, Vitamin D2 and cholecalciferol, vitamin D3. Recent data suggest that two forms may be equivalent. I continue however to recommend D3 until we know more.

Bottom-line, vitamin D is important to our health, always however, speak with your doctor first about any vitamin or supplement to be sure it is safe for you.