The effects of bovine colostrum supplementation on in vivo immunity following prolonged exercise: a randomised controlled trial

Background Bovine colostrum (COL) has been advocated as a nutritional countermeasure to exercise-induced immune dysfunction but there is a lack of research with clinically relevant in vivo measures. Aim To investigate the effects of COL supplementation on in vivo immunity following prolonged exercise using experimental contact hypersensitivity (CHS) with the novel antigen Diphenylcyclopropenone (DPCP). Methods In a double-blind design, 31 men were randomly assigned to COL (20 g/day) or placebo (PLA) for 58 days. Participants ran for 2 h at 60% maximal aerobic capacity on day 28 and received a primary DPCP exposure (sensitisation) 20 min after. On day 56, participants received a low dose-series DPCP challenge to elicit recall of in vivo immune-specific memory (quantified by skinfold thickness 24 h and 48 h later). Analysis of the dose response curves allowed determination of the minimum dose required to elicit a positive response (i.e. sensitivity). Results There was no difference in summed skinfold thickness responses between COL and PLA at 24 h (p = 0.124) and 48 h (p = 0.405). However, sensitivity of in vivo immune responsiveness was greater with COL at 24 h (p < 0.001) and 48 h (p = 0.023) with doses ~2-fold greater required to elicit a positive response in PLA. Conclusions COL blunts the prolonged exercise-induced decrease in clinically relevant in vivo immune responsiveness to a novel antigen, which may be a mechanism for reduced illness reports observed in previous studies. These findings also suggest that CHS sensitivity is highly relevant to host defence.