A clinical review published in The Journal of the American Osteopathic Association concluded that nearly 1 billion people worldwide may have deficient or insufficient levels of vitamin D due to two specific factors: inadequate sun exposure related to sunscreen use and an increase in the prevalence of chronic disease.

The study also found that 95 percent of African-American adults may have vitamin D deficiency or insufficiency. Vitamin D variations among races are attributed to differences in skin pigmentation.

“People are spending less time outside and, when they do go out, they’re typically wearing sunscreen, which essentially nullifies the body’s ability to produce vitamin D,” says Dr. Kim Pfotenhauer, D.O., assistant professor at Touro University and a researcher on this study. “While we want people to protect themselves against skin cancer, there are healthy, moderate levels of unprotected sun exposure that can be very helpful in boosting vitamin D.”

Dr. Pfotenhauer also says that chronic diseases like type 2 diabetes and those related to malabsorption, including kidney disease, Crohn’s and celiac disease, greatly inhibit the body’s ability to metabolize vitamin D from food sources.

Fast Facts About Vitamin D

Considered a hormone rather than a vitamin, vitamin D is produced when skin is exposed to sunlight. Vitamin D receptors are found in virtually every cell in the human body. As a result, it plays a wide role in the body’s functions, including cell growth modulation, neuromuscular and immune function and inflammation reduction.

Symptoms for insufficient or deficient vitamin D include muscle weakness and bone fractures. People exhibiting these symptoms or who have chronic diseases known to decrease vitamin D, should have their levels checked and, if found to be low, discuss treatment options. However, universal screening is probably unnecessary or not prudent unless in the case of significant symptoms or chronic disease.

Currently, insufficient vitamin D is defined as between 21 and 30 ng/mL and vitamin D deficiency is considered below 20ng/mL by the Endocrine Society.

How Can You Increase Your Vitamin D Intake?

Here’s some good news you can offer clients who may be at risk of vitamin D deficiency: Increasing and maintaining healthy vitamin D levels can be as easy as spending five to 30 minutes in midday sun twice per week. The appropriate time depends on a person’s geographic location and skin pigmentation—lighter skin synthesizes more vitamin D than darker skin. It is important to forgo sunscreen during these sessions because SPF 15 or greater decreases vitamin D3 production by 99 percent.

“You don’t need to go sunbathing at the beach to get the benefits,” says Dr. Pfotenhauer. “A simple walk with arms and legs exposed is enough for most people.”

Vitamin D can, of course, be consumed through food, which is good news for those who have to stay out of the sun. Vitamin D3 occurs naturally in cod liver oil, fish oil and wild fish such as salmon, sardines, herring and cod. The vitamin D from these sources is metabolized by the same pathway as the D3 derived from sunlight, which is ideal. Vitamin D3 is also found in blood sausage, some organ meats, butter and eggs from pastured hens. Other food sources such as milk and breakfast cereals are fortified with vitamin D. Additionally, Dr. Pfotenhauer says that supplements can be a good option, as they are effective and pose few risks, provided they are taken as directed and a physician is consulted beforehand.

“Science has been trying to find a one-to-one correspondence between vitamin D levels and specific diseases,” explains Dr. Pfotenhauer. As a result, ongoing research studies are trying to determine whether vitamin D deficiency has a role in multiple sclerosis, autoimmune disorders, infections, respiratory disease, cardiometabolic disease, cancer and fracture risk.

Given vitamin D’s ubiquitous role in the body, however, it is clear that maintaining sufficient vitamin D is essential to overall health and well-being.