According to studies, vitamin D deficiency is a widespread phenomenon worldwide. It affects 42% of adults in the US. Optimal vitamin D levels contribute to normal blood calcium levels, the maintenance of normal bones, and the maintenance of normal muscle function. And a deficiency can not only be the case in older people. Professional athletes can also be affected.
Studies of vitamin D levels in National Football League (NFL) players showed that 69% to 80% of players had inadequate levels. These findings suggest implications for athletic performance and risk of injury. In fact, a previous study correlated low vitamin D levels with higher injury rates in NFL athletes.
A recent study published in 2017 (1) aimed to determine the association between serum vitamin D levels and the prevalence of muscle strains and core muscle injuries in elite-level college athletes at the annual NFL Scouting Combine. A normal vitamin D level has been determined to be equal to or greater than 32 ng/mL. A value of 20-31 ng/mL was considered inadequate, while a value below 20 ng/mL was considered a deficiency. The classification of injuries included lower extremity muscle strains, which were defined as adductor/groin, hamstrings, hip flexors, or quadriceps strains, and lower abdominal muscle injuries, which were diagnosed as trunk muscle injuries.
A total of 214 NFL combine athletes were included in the study. Of these, 126 players (59%) had low serum vitamin D (less than 32 ng/mL), including 22 athletes (10%) with high vitamin D deficiency (less than 20 ng/mL).
There were differences in parentage and injury history. Athletes who had frequently injured themselves in the past had significantly lower mean serum vitamin D levels than uninjured athletes. Of 13 players who missed at least one game due to a lower extremity strain or core muscle injury, 86% had inadequate vitamin D levels. Afro-American/Black athletes had significantly lower vitamin D levels compared to white athletes.
The researchers estimated that players with inadequate vitamin D levels were 1.86 times more likely to have a lower extremity strain or core muscle injury than players with adequate vitamin D levels. Additionally, players with inadequate vitamin D levels are 3.61 times more likely to suffer a hamstring strain than players with normal vitamin D levels.
The main finding of the study is that players with an injury history of lower extremity strains or core muscle injuries had significantly lower average vitamin D levels than the uninjured players and that inadequate vitamin D levels are common among NFL combine athletes.
Optimal vitamin D levels are controversial and there is no golden standard. The researchers refer to literature that defines an optimal level of between 30 and 50 ng/mL and point out that an increase in performance can occur from a vitamin D level of 30 ng/mL. Although this study did not consider supplementation for athletes, the researchers speculate that optimal vitamin D levels may help prevent muscular injury.
Good luck with vitamin D!
Source: 1. https://www.ncbi.nlm.nih.gov/pubmed/29275983
Image: A strain.