Over half of collegiate athletes trying out for the National Football League (NFL) surveyed (59%) displayed inadequate vitamin D levels with 10% identified as being deficient in the vitamin.
Findings in these players, who had a history of lower extremity muscle strain and core muscle injury, were described as “widespread” by the New-York based researchers.
“Our study revealed that 86% of players who missed competition because of strain injury had inadequate levels of vitamin D,” the researchers said.
“This could be related to physiologic changes that occur in muscle composition in deficient states.”
The findings are of notable concern given that the NFL is a contact sport in which the risk of injury is high. Taking a proactive approach to injury prevention, which includes maintaining optimal nutritional status, remains key to success in the sport.
Study draft
Using a cohort of 214 athletes from the 2015 NFL combine, the study collected serum vitamin D levels as well as age, race, body mass index, position and injury history specific to lower extremity muscle strain or core muscle injury.
Specially, serum 25-hydroxyvitamin D levels of less than 32 nanograms per millilitre (ng/mL) were defined as normal, 20-31 ng/mL as insufficient less than 20 ng/mL as deficient.
Lower extremity muscle strain or core muscle injury was present in 50% of athletes, which was associated with lower vitamin D levels.
Athletes with a positive injury history also showed significantly lower vitamin D levels as compared with uninjured athletes.
However, vitamin D groups showed no differences in age and body mass index.
“The majority of elite level athletes participating at the NFL combine had inadequate levels of vitamin D,” said the team, who are based at New York's Hospital for Special Surgery (HSS).
“Diminished vitamin D levels in this group were associated with a history of lower extremity strain or core muscle injury, which may potentially have career or performance-based implications if not addressed. “
What is the NFL Combine?
The NFL Scouting Combine occurs every February in which NFL coaches, general managers, and scouts are invited to a week-long event showcasing college football players’ performance in physical and mental tests.
Tests/evaluations include, bench press (225 lb repetitions), vertical and broad jump, sprints and position-specific drills.
Steelers and Giants
Vitamin D levels and their link to injury in professional athletes is not a new observation. Players competing in the NFL for the Pittsburgh Steelers have also been subject to a study in which 69% of team members had inadequate levels of vitamin D.
These levels were collected during preseason training camp or the preceding offseason period. Those with the lowest vitamin D levels more vulnerable to being released from the team.
This trend was also noted in a 2011 study that vitamin D levels of 89 professional football players from the New York Giants showing fluctuating levels of vitamin D.
Findings revealed 27 players (30.3%) had deficient total 25-hydroxy vitamin D levels (below 20 ng/mL), and 45 players (50.6%) had insufficient vitamin D levels (between 20 and 31.9 ng/mL). Only 17 players (19.1%) had values within normal limits (above 32 ng/mL).
The study, led by Dr Michael Shindle, an orthopaedic surgeon from Summit Medical Group, in New Jersey, also reported an association between vitamin D deficiency and an increased rate of muscle injury.
Vitamin D plays a number of roles in the body, including the maintenance of healthy calcium levels and subsequent bone health. Its role in professional sports has been investigated by sports nutritionists, who believe peak athletic performance can only be achieved when vitamin D levels are 30 - 50 ng/mL.
“Although our study did not address supplementation for athletes, we speculate that vitamin D supplementation could help prevent musculoskeletal injury in this group,” the HSS team said.
“Recommendations for vitamin D supplementation should also include routine laboratory surveillance to assess patient response and baseline levels.”
Source: Arthroscopy: The Journal of Arthroscopic & Related Surgery
Published online ahead of print: doi.org/10.1016/j.arthro.2017.10.005
“The Association of Vitamin D Status in Lower Extremity Muscle Strains and Core Muscle Injuries at the National Football League Combine.”
Authors: Brian Rebolledo et al.