More than half of college football athletes participating in the NFL Scouting Combine had inadequate levels of vitamin D, leaving them more susceptible to muscle injuries, according to a study at Hospital for Special Surgery.
Vitamin D has been shown to play a role in muscle function and strength. While most prior studies have focused on older adults as a group most likely to experience the harmful effects of inadequate vitamin D, little research has examined the impact on muscle injury and function in high performance athletes.
The researchers set out to determine if there was a relationship between serum vitamin D levels and lower extremity muscle strains and core muscle injury, or "sports hernia," in college football players.
The study included 214 college athletes, average age 22, who took part in the 2015 NFL combine, where coaches, general managers and scouts evaluate top college football players hoping to make it into the big leagues.
Baseline data was collected, including age, body mass index (BMI), injury history, and whether they had missed any games due to a lower extremity muscle strain or core muscle injury.
Their vitamin D levels were measured by a blood test. Levels were defined as normal (32 ng/mL), insufficient (20 -- 31 ng/mL), and deficient (< 20 ng/mL).
Low vitamin D found in almost two-thirds of athletes
NFL combine athletes at greatest risk for lower extremity muscle strain or core muscle injury had lower levels of vitamin D.
A total of 126 players (59%) were found to have an abnormal serum vitamin D level, including 22 athletes (10%) with a severe deficiency.
Researchers found a significantly higher prevalence of lower extremity muscle strain and core muscle injury in those who had low vitamin D levels. Fourteen study participants reported missing at least one game due to a strain injury, and 86% of those players were found to have inadequate vitamin D levels.
Awareness of the potential for vitamin D inadequacy could lead to early recognition of the problem in certain athletes. This could allow for supplementation to bring levels up to normal and potentially prevent future injury, the researchers stated.
While the findings are significant for high performing athletes, there may be a message for the general population as well. Adequate vitamin D is essential for musculoskeletal structure, function and strength.
How to get vitamin D
Sometimes called the "sunshine vitamin," vitamin D is produced by the skin when exposed to sunlight. Sun avoidance and the use of sunscreen may in part account for low vitamin D levels in the population.
Daily-recommended vitamin D intakes (RDAs), updated in 2011, are 400 international units (IU) for infants, 600 IU for children aged one to adults aged 70, and 800 IU for older adults. Some people, however, may need more vitamin D to maintain a sufficient blood level. The safe upper limit is 4000 IU per day.
Foods that provide vitamin D naturally, which are few and far between, include salmon (447 IU per 3 ounces) and tuna (154 IU per 3 ounces). Eggs (41 IU per yolk) and cheese (14 IU per 2 ounces of cheddar) provide a little. Fluid milk, many non-dairy beverages and some brands of orange juice are fortified with vitamin D (100 IU per one cup).
If you drink two or more servings (1 cup each) of milk or vitamin D fortified non-dairy milk, a 400 IU supplement of vitamin D may suffice.
If you don’t drink cow’s milk or fortified non-dairy beverages, I recommend a 1000 IU vitamin D supplement year round. Most multivitamins contain 400 IU of vitamin D but some manufacturers have started adding 1000 IU. Single supplements of vitamin D typically come in 400 and 1000 IU doses.
Source: Hospital for Special Surgery
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