No firm evidence exists to support or refute the role of hydration in the treatment of the common cold, but current expert opinion highly recommends keeping properly hydrated to prevent and treat the common cold.
Dehydration leads to an increase in cortisol levels, which suppresses the immune system.
Dehydration is suggested to be one of the possible mechanisms leading to immune dysfunction in marathon runners.
Dehydration has been found to decrease salivary rate and Salivary immunoglobulin A, which is one of the first lines of defense of the immune function on foreign bacteria.
Endurance athletes such as marathon runners, triathletes, ultra marathon runners training have been noted to be at a particularly high risk of upper respiratory tract infection due to intense training; it is important for these athletes to stay properly hydrated during training to avoid infection.
Key Learning: Maintaining appropriate hydration during exercise keeps the immune system functioning properly and can help prevent the risk of upper respiratory tract infections.
Read the Korey Stringer Institute (KSI) study on "Immune Fuction: Basic Considerations of Exercise and Hydration."