Acute bovine colostrum boosts neutrophil oxidative burst and salivary lysozyme after prolonged cycling

Prolonged and intense physical exercise is known to induce transient immune suppression, often referred to as the 'open window' phenomenon, which increases susceptibility to upper respiratory tract infections. Current strategies to mitigate this include adequate rest and nutrition, but specific interventions to bolster immune function during this critical period are sought. Bovine colostrum (BC), rich in immunoglobulins, growth factors, and antimicrobial peptides like lactoferrin and lysozyme, has emerged as a potential natural immunomodulator. Understanding how BC acutely impacts specific innate immune responses, such as neutrophil function and mucosal immunity, in the context of exercise stress could offer a valuable prophylactic strategy for athletes.

This double-blind, placebo-controlled crossover trial involved 16 healthy, recreationally active males. Participants completed two trials in a randomized, counterbalanced order, consuming either bovine colostrum or an isoenergetic placebo. The acute dosing regimen for bovine colostrum was 30g 1 hour pre-exercise, 5g immediately pre-exercise, and another 5g midway through a 2.5-hour cycling session at 15% Δ. Venous blood and unstimulated saliva samples were collected at baseline, 1 hour post-consumption (pre-exercise), immediately post-exercise, and 1 hour post-exercise. A mechanistic sub-study further investigated whether plasma from colostrum-consuming participants directly enhanced neutrophil function using fMLP-stimulated neutrophil oxidative burst assays.

Compared to placebo, bovine colostrum supplementation led to a significantly greater fMLP-stimulated blood neutrophil oxidative burst, showing approximately a 15% difference across timepoints (trial, p < 0.05). This indicates an enhanced capacity of neutrophils to produce reactive oxygen species, a key component of innate immunity. The mechanistic sub-study corroborated this, demonstrating that fMLP-stimulated neutrophil oxidative burst was enhanced when whole blood was pre-incubated with plasma obtained 1 hour after colostrum consumption, suggesting bioavailable components or metabolites are responsible. Furthermore, there was a greater salivary lysozyme concentration observed immediately post-exercise in the bovine colostrum trial (trial × time interaction, p < 0.05), indicating improved mucosal immunity.

Bacterial-stimulated blood neutrophil elastase release was also significantly higher 1 hour post-exercise in the bovine colostrum group (trial × time interaction, p < 0.05), pointing to enhanced antimicrobial enzyme activity. However, no significant effects were observed for leukocyte trafficking, PMA-stimulated neutrophil oxidative burst (a different activation pathway), salivary secretory immunoglobulin A, or salivary lactoferrin, suggesting specific rather than broad immune modulation.