Ever wonder why your doctor or physical therapist might tell you that 20 minutes of sunlight is good? Or why so many individuals are placed on a vitamin D supplement during the winter in upstate NY?
Well, the body uses sunlight to produce this (not technically a vitamin) vitamin. I say “not technically” a vitamin because to be classified as a vitamin, the human body must not produce it. The only natural food sources of vitamin D are fish and egg yolks, which is why many other common foods are fortified with this vitamin. Despite this, many people may be at risk for deficiency.
Some reasons for this deficiency include diet, obesity, low consumption levels of vitamin D over time, lack of sun exposure, dark skin, and GI tract diseases preventing absorption. Also, the kidneys’ ability to convert vitamin D to its active form decreases over time.
It works like this: Sunlight (or ultraviolet B, UVB) turns a chemical in your skin into vitamin D3, which is then carried to your liver and your kidneys, where it is transformed into active vitamin D. Vitamin D’s best-known role is to keep bones healthy by increasing the intestinal absorption of calcium. Without enough vitamin D, the body can only absorb 10 to 15 percent of dietary calcium, but 30 to 40 percent absorption is the rule when vitamin reserves are normal. This is why getting enough vitamin D is especially important for women, because they have a much higher incidence of osteoporosis in later adulthood.
But men, don’t think you are safe! Vitamin D deficiencies were rare when most men rolled up their sleeves to work in sunny fields. But as work shifted from farms to offices, this reality changed. Because pigmentation can reduce vitamin D production in the skin by over 90 percent, nonwhite populations are at particular risk. Deficiencies are also common in patients with intestinal disorders that limit absorption of fat and those with kidney or liver diseases that reduce the conversion of vitamin D to its active form, calcitriol.
In addition, for both men and women, this popular vitamin has receptors that are present in many other organs — from the prostate to the heart, blood vessels, muscles, and endocrine glands. And current research suggests that good things happen when vitamin D binds to these receptors. The main requirement is to have enough vitamin D — but many Americans don’t.
As summer winds down and you begin to have less opportunity to get your daily dose of sunlight, it may be beneficial to have your vitamin D levels tested to ensure you aren’t at risk for vitamin D deficiency.
For more information, including tips for getting adequate vitamin D, please contact us at firstname.lastname@example.org.