KUMC researchers show how vitamin D may ease muscle pain

September 29, 2011

By KUMC News

Peter Smith, PhD, and Sarah Tague, PhD

More than half of all adults in the United States may suffer from back and other types of musculoskeletal pain, a problem estimated to cost the economy in excess of $50 billion annually. Studies have shown that people with back and other types of musculoskeletal pain are likely to be deficient in vitamin D, and that in many cases vitamin D supplements can reverse that pain. Now a new study by scientists at the University of Kansas Medical Center, featured in this week's Journal of Neuroscience, may explain exactly how vitamin D helps ease muscle pain.

KU Medical Center researchers found that when laboratory rodents didn't get enough vitamin D, they appeared to be more sensitive to pressure applied to their calf muscles than rats on a normal diet. "We were excited to find that vitamin D-deficient rodents mimicked human muscle pain so closely," says Sarah Tague, PhD, a postdoctoral fellow in the Institute for Neurological Disorders and Department of Molecular and Integrative Physiology, and the lead author on the paper.

The researchers wanted to know how vitamin D deficiency leads to muscle pain. Examining the rodent muscle tissue, they found that rats with low vitamin D had a higher number of pain-sensing nerve fibers. "Pain is an important early warning sign. It tells us when we are in danger of doing physical damage to ourselves," says Peter G. Smith, PhD, the senior investigator on the study and director of KU Medical Center's Institute for Neurological Disorders. "Our body tissues are equipped with special pain-sensing nerves we call nociceptors. These nerves are our guardians, protecting us from injury. When we use our muscles to the point where they may become damaged, our nociceptors warn us to change our behavior by providing a painful signal. However, if those nerves become too sensitive, we end up experiencing chronic pain."

Tague and Smith counted the number of nociceptor nerves in the rodents' muscles and found that within a month of being on a vitamin D-deficient diet, these nerves had doubled. "That is a remarkably rapid change," Tague says. "Some rats that didn't get enough vitamin D showed signs of muscle sensitivity as early as two weeks after starting the deficient diet."

Vitamin D has been the focus of much media attention in recent years. Other than its ability to prevent bone deterioration, its benefits have remained controversial, particularly in light of a recent report by the Institute of Medicine that questioned the benefits of supplements. "Much of the controversy surrounding vitamin D is due to the difficulty in identifying the biological underpinnings of what has been largely anecdotal evidence by patients extolling the virtues of supplements," Smith says. "A significant aspect of our study is that it provides strong biological evidence as to why vitamin D supplements may be effective."

Vitamin D supplements are safe and inexpensive, making them ideal for preventing and treating chronic muscle pain. "We hope our findings lead to a greater clinical acceptance of Vitamin D as a therapy for muscle pain," Smith says.

Smith and Tague's work was supported by the National Institute of Child Health and Human Development, National Center for Complementary and Alternative Medicine, the National Institute on Aging and the Kansas Intellectual and Developmental Disabilities Research Center.

Last modified: Oct 21, 2011