Nutrition, exercise and the immune system

Strenuous exercise, especially if prolonged or intense, causes a temporary depression in various aspects of immune function that can last between three and twenty-four hours, depending on the intensity and duration of the exercise and what parameter of immune function is analyzed.
Therefore, exercise can be considered as a factor that burdens the immune system and can cause immunosuppression, similar to other stress factors (surgery, traumatic injury, acute myocardial infarction).

During this post-exercise window period in which immune system function is suppressed, viruses and bacteria are more likely to enter the body and therefore increase the risk of infection. In fact, exercise-induced immune system disturbances are associated with an increased risk of upper respiratory tract infection (URIs), especially during intense training periods and one to two weeks after endurance events
Various nutritional factors have been evaluated for their potential effects on reducing the immune response, oxidative stress, and exercise-induced inflammation. However, most are not effective, with the exception of some polyphenolic supplements (a group of chemicals found in fruits and vegetables) such as quercetin, β-glucans, etc.
Athletes with rigorous training regimens and especially endurance athletes are interested in maintaining a strong immune system. This can be achieved by using carbohydrate-based beverages and mixtures of bioactive substances (eg polyphenols) that aim to reduce the risk of infection, alleviate oxidative stress and inflammation caused by exercise. Likewise, this strategy can be combined with others that help maintain optimal immunity and health, such as following a healthy diet, avoiding overtraining, sleeping well, avoiding rapid weight loss, etc.