Vitamin D plays a key role in maintaining health and function of skeletal muscle but can it be used to aid recovery after exercise?
Vitamin D plays a role in numerous processes and pathways throughout the body one of which is the modulation of inflammation. It is through this modulation that vitamin D affects muscle function by stimulating protein synthesis and cellular growth and therefore muscle recovery.
A meta-analysis by Tomlinson et al explored the role of vitamin D on muscle strength and they found supplementation resulted in a positive outcome on strength in the upper and lower limbs.
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Even though we know that vitamin D plays a role in muscular strength and in the inflammatory process only a few studies have demonstrated an improvement in muscular recovery. Therefore this systematic review published in nutrients aimed to analyse if the evidence supports a role for vitamin D in muscular recovery.
This systematic review with meta-analysis was carried out according to the PRISMA guidance but wasn’t pre-registered on PROSPERO. PubMed, MEDLINE, WoS, Google Scholar and Scopus were the databases used for the search.
The search involved a combination of MeSH and free-text terms and is as follows:
(“Vitamin D” [All Fields] OR “calciferol” [All Fields]) AND (“Muscle Damage” [All Fields] OR “Creatine kinase” [All Fields] OR “CK” [All Fields] OR “Lactate” [All Fields] OR “LDH” [All Fields]“ OR “Mb” [All Fields]“)
To be included in the review articles had to meet the following criteria:
- the presence of an experimental group supplemented with vitamin D before or during the exercise compared with an identical placebo group
- assess the effects of vitamin D on exercise tests or in competition
- randomised designs published in non-English languages
- contain information regarding vitamin D dosage and timing
Articles were excluded if studies were not performed in athletes and if no placebo or control group was used. Risk of bias was assessed without using a formalised tool. Instead selection, performance and detection bias was evaluated.
Standardised mean difference was used to quantify changes in variables related to muscle damage calculated using Hedges’s g and inverse of variance to calculate overall effect and 95% CI. Random effects model using the DerSimonian and Laird method was used for the variable amount of vitamin D required in each study.
In total six studies involving, 198 participants, were included within the review with five being blinded-RCTs. Dosage of vitamin D ranged from 600 – 300,00 IU/ day either in tablet or submit injection form for between 3 and 12 weeks. Participant age ranged from 20-40 years of age and the most commonly used form of exercise used to assess recovery was eccentric exercise. Overall there was a lack of consistent protocols used.
Overall vitamin D produced no significant effects on creatine kinase levels post exercise (SMD -0.10 95% CI -0.70 to 0.51 p= 0.77225). No significant difference in effect of lactate dehydrogenase levels either (SMD, −0.06; 95% CI, −0.69, to 0.58 p = 0.7987). There was also no significant effect of vitamin D supplementation on circulating myoglobin levels either (SMD, 0.08; 95% CI, −1.08, to 1.24 p = 0.8779).
It’s no doubt that vitamin D affects muscle function and structure as we know that vitamin D deficiency causes muscle weakness. We also know that in some studies vitamin D supplementation improves some aspects of performance and prevent injuries in sports people. However the results of this systematic review does not demonstrate that vitamin D improves recovery post-exercise.