Low vitamin D levels are an unintended consquence of spending more time inside and covered up to reduce the risk of skin cancer.
Vitamin D is often called the “sunshine vitamin,” because sunlight exposure to skin is the best and only natural source for humans to get it. It's known to be essential for bone health, but research shows it's also crucial for fighting all kinds of illness and disease.
"If you're low on vitamin D, your immune system does not function as well or you're more susceptible to infections,” said Dr. Richard Honaker, a family practice physician. “There's a greater incidence of heart attacks and strokes in people that are vitamin D-deficient versus people who are OK on their vitamin D levels.”
The Cooper Clinic in Dallas routinely tests for vitamin D levels during routine physical exams and sees lots of patients who unknowingly have a deficiency.
“We're finding that when we measure thousands of patients, the vast majority of them are low,” said Todd Whitthorne, the president and chief operating officer of Cooper Concepts Inc., a division of The Cooper Aerobics Center in Dallas.
Honaker said he sees the same trend.
"It's sort of epidemic, so to speak,” he said. “It's not really a disease, like the epidemic that you spread, it's epidemic (in that) everybody seems to be low."
Whitthorne said because people are getting less vitamin D because many spend so much time indoors.
“If we go outside, we're taught to wear sunscreen because we want to lower the risk of skin cancer -- which makes sense -- but a sunscreen of SPF 15 or greater blocks 99 percent of the synthesis of vitamin D," he said.
Cathy Wood discovered she had low levels during a routine physical at the Cooper Clinic and had to start taking prescription-strength supplements.
"I drink a lot of milk, and I thought my vitamin D levels would be fine,” she said.
Wood said she also eats a lot of fish and gets out in the sun, but found that wasn’t enough.
Few foods are fortified with or naturally contain vitamin D, so sunshine and supplements are key. How much a person needs depends on a variety of factors, including health, weight, sunscreen usage and skin color.
Darker-skinned people are more at risk. The American Medical Association says nearly all non-Hispanic blacks and most Mexican-Americans have insufficient vitamin D levels.
Low vitamin D levels are linked to chronic pain, fatigue, depression, osteopororis and more.
“And there are a lot of people who just hurt," Honaker said. “When you give them vitamin D, they have more energy, they have less joint aches and pains and they just generally feel more rigorous.”
Wood said she feels healthier since starting vitamin D supplements, which also help her body absorb calcium.
"In the last two years, I have not had one cold, and I really attribute it to the vitamin D,” she said.
Doctors say the current recommended daily doses of vitamin D are inadequate, and that just about everyone should be get more of it in one form or another.
"I would recommend that every patient, every person in America, get their vitamin D checked, because so many people are low and the ramifications of having low vitamin D are so severe," Honaker said.
Many health groups recommend adults take 1,000 to 2,000 units of vitamin D daily -- five to 10 times the old recommendation. Doctors expect federal guidelines to be revised in the coming years.