Don’t Throw Away Your D’s
About a month ago, I read a news report about the Mt. Olive,NJ school district’s decision to eliminate the grade of “D” from student report cards this fall. Only A’s, B’s, C’s, and F’s would be used. The district superintendent was quoted as saying, “D’s are simply not useful in society. It’s a throwaway grade. No one wants to hire a D-anything, so why would we have D-students and give them credit for it?”
While this school district may have an arguable point about the “D” as a grade, there’s another “D” that shouldn’t be discarded by anyone.
Recent studies in several medical and nutritional journals have illuminated the importance of vitamin D for much more than the prevention of rickets, which is the extent of what most of us learned in high school biology or health class. Most of the research over the past decade has focused on the evidence supporting the relationship of adequate levels of vitamin D to bone health, immune function, and modulation of the inflammatory response. Moreover, deficiencies in vitamin D have been linked to an increased risk of chronic and autoimmune disorders including high blood pressure, rheumatoid and osteoarthritis, inflammatory bowel disease, depression, and even certain types of cancer.
Historically, there seemed to be little cause for concern since, as most of us have assumed, we obtain the bulk of our stores of vitamin D through exposure to sunlight, as well as from fortified foods. But now there is compelling evidence that indicates there is a virtual epidemic of vitamin D insufficiency among adults and children worldwide, especially in those who live in northern (above the 35° parallel – roughly the position of Washington, DC) latitudes. At those locales, the natural synthesis of vitamin D through exposure of the skin to sunlight is greatly compromised during the winter months, due to the low angle of the sun. The body’s ability to produce vitamin D in this manner is further reduced yearlong by smog, cloud cover and, perhaps most significantly, the conscious effort of many in recent years to limit exposure of the skin to sunlight.
This information, while being of concern to the general population, may not seem to have any special relevance to runners specifically,but a recent review of the subject in the journal Current Sports Medicine Reports [Vol.9, No. 4, 2010] brings to light some interesting assertions that should be of interest to all athletes.
According to the authors, a relatively little-known consequence of vitamin D insufficiency is a higher incidence of musculoskeletal pain and weakness. In support of this assertion,they cite a multitude of studies on the subject, including:
- A study at an inner-city clinic in Minnesota that found that 93% of individuals with persistent, non-specific muscle pain had blood concentrations of the vitamin D marker lower than accepted minimal levels.
- A study in south Asian women found that chronic pain was 3.5 times more common in those with vitamin D insufficiency.
- Vitamin D status was found to correlate with jump height, velocity, and power in young (12-14 years) girls.
- In patients with low back pain who initially had low vitamin D stores, a 3-month supplementation program resulted in clinically significant reductions in pain levels.
- A study of Finnish military recruits showed an increased risk of stress fractures when vitamin D levels fell below minimal requirements.
The authors of the article are quick to point out that none of the studies were specific to athletes and,importantly, none were randomized, controlled investigations. Additionally, they state that athletes may not require any more vitamin D than the general population, but nonetheless conclude that sports nutritionists and physicians should routinely assess vitamin D levels in athletes and make appropriate recommendations. They recommend that all athletes be screened annually (there is a simple blood test that your physician can order) for vitamin D levels, and sooner if there is a history of stress fracture, frequent illness, bone and joint injury, or muscle pain and weakness.
The “fix” for those whose levels are low is relatively simple and inexpensive (supplementation via capsules) and there is virtually no risk of overdose when taken as directed. In this case, an ounce of prevention may very well be worth much more than a pound of cure.