But does not having enough vitamin D cause pain ? That's not yet clear. But here's what you need to know about vitamin D and chronic pain .

Many Americans are running low on vitamin D. A study published in the Archives of Internal Medicine in 2009 showed that vitamin D levels have plummeted among all U.S. ages, races, and ethnic groups over the past two decades.

Over the past 10 years, several researchers have found an association between extremely low vitamin D levels and chronic, general pain that doesn’t respond to treatment.

Not getting enough vitamin D in your system may be linked to chronic pain .

Boosting Vitamin D, Easing Pain

Greg Plotnikoff, MD, senior consultant with the Allina Center for Health Care Innovations in Minnesota, still remembers the woman in her 40s who told him that he was the 30th doctor she’d seen.

“Twelve of them had told her she was crazy,” says Plotnikoff, formerly an associate professor of internal medicine and pediatrics at the University of Minnesota Medical School. “She had weakness, achiness, fatigue -- three pages worth of symptoms. Doctors had offered her antidepressants and seizure medications and all kinds of things that didn’t work. I checked her vitamin D levels -- and they came back barely measurable.”

After six months on an aggressive, high-dose prescription vitamin D replacement, the woman could cross off every symptom on her three-page list. “I knew I wasn’t crazy!” Plotnikoff says she told him.

That's just one woman. Her case doesn't mean vitamin D will erase pain for everyone.

However, Plotnikoff published a study in 2003 on 150 people in Minneapolis who came to a community health clinic complaining of chronic pain. Virtually all of them -- 93% -- had extremely low vitamin D levels.

Vitamin D blood levels of 30-40 ng/mL are considered ideal. The average level in Plotnikoff’s study was about 12, and some people had vitamin D levels so low they were undetectable.

“The group with the lowest levels of vitamin D were white women of childbearing age,” Plotnikoff says. “Most of them were dismissed by their doctors as depressed or whiners. They attributed their pain to an inability to manage stress. But after we replenished their vitamin D, these people said, ‘Woo hoo! I’ve got my life back!’”

Plotnikoff notes that vitamin D is a hormone. "Every tissue in our bodies has [vitamin] D receptors, including all bones, muscles, immune cells, and brain cells," he says.

And in March 2009, researchers at the Mayo Clinic published a study showing that patients with inadequate vitamin D levels who were taking narcotic pain drugs required nearly twice as much medication to control their pain as did patients with adequate D levels