Oral spray wintertime vitamin D₃ supplementation has no impact on inflammation in Gaelic footballers

Abstract

Vitamin D inadequacy [total 25(OH)D <50 nmol/L] is widespread in athletes. The biologically active metabolite, 1,25-dihydroxyvitamin D, may be involved in regulating inflammation although in vitro findings have not been consistently replicated in human intervention trials. This study, conducted at a latitude of 55°N, aimed to assess inflammatory biomarkers in Gaelic footballers before and after a wintertime vitamin D intervention. Samples from a 12-week double-blind, randomized, placebo-controlled trial, in which 42 Gaelic footballers received 3000 IU (75 μg) vitamin D daily or placebo via oral spray solutions, were analysed for a range of inflammatory biomarkers. Cytokines (interleukin-8 and tumor necrosis factor-α), cathelicidin and high sensitivity C-reactive protein were quantified by multiplex assay, enzyme-linked immunosorbent assay and clinical biochemistry, respectively. White blood cell, lymphocyte, and neutrophil concentrations were determined by full blood profile. Data on total 25-hydroxyvitamin D, measured by LC-MS/MS, were available from the previous study. Vitamin D supplementation significantly increased mean total 25-hydroxyvitamin D concentrations from 47 to 84 nmol/L (P = 0.006); yet this had no effect on white blood cell count (P = 0.699), lymphocyte (P = 0.694), neutrophil (P = 0.594), interleukin-8 (P = 0.334), tumor necrosis factor-α (P = 0.587), cathelicidin (P = 0.745) or high sensitivity C-reactive protein concentration (P = 0.621) compared to placebo. 12-weeks vitamin D supplementation did not impact the immune profile of Gaelic footballers. This is likely because biomarkers were within their respective normal range or at a concentration similar to that of the general population at baseline. Future studies are encouraged to use inflammation as their primary outcome measure and recruit athletes at risk of compromised immunity.

Effects of vitamin D supplementation on muscle function and recovery after exercise‐induced muscle damage: A systematic review

“…One study was added from the reference lists of selected articles, and the final number of studies in this systematic review was 11. 43,44,[47][48][49][50][51][52][53][54][55] A summary of the search process is depicted in Figure 1.…”

“…Seven studies were conducted with men, 43,47,48,50,52,53,55 three with women 47,51,54 and one with men and women. 44 The mean age of the participants ranged from 15.90 ± 0.29 years to 42.40 ± 7.59 years. Five studies evaluated the effects of vitamin D supplementation on sedentary to moderately active people, [47][48][49]53,55 five studies on highly active people 43,44,50,52,54 and one did not mention the participants' fitness level.…”

“…30 Nonetheless, not all research studies carrying out a vitamin D supplementation have observed significant reductions in inflammatory markers after exercise. 43,44 Due to the contradictory results observed of the effects of vitamin D supplementation on muscle function and recovery after exercise and because we have not found any review on this subject, this systematic review aims to summarise the effects of vitamin D supplementation on muscle damage and recovery after EIMD in humans.…”

Influence of exercise and vitamin D on the immune system against Covid-19: an integrative review of current literature

“…On the other hand, in a supplementation protocol of 3,000 IU vitamin D for 12 weeks in a population of soccer athletes during the winter, studies [ 59 ] did not observe effects on the participants' immune profile. A possible cause would be that the immunological components evaluated were already, at the beginning of the study, at their normal or similar intervals to the general population.…”

“…It also plays a direct role through VDR-RXR (Vitamin D and Retinoid X Receptors, respectively) signaling, which then promotes the production of LL-37, an endogenous antimicrobial cathelicidin that acts by destabilizing the membrane of bacteria and fungi that invade the body [40,45,55,56]. In the case of viruses, vitamin D acts more directly by compromising the protein envelope and preventing the entry of genetic material into cells [57][58][59]. Allied to this, vitamin D is also responsible for suppressing the production of pro-inflammatory cytokines, such as IL-2, IL-6 and IL-17 [55,60,61].…”