Is moderate exercise good or bad for your immune system?
Moderate exercise (sessions up to 45 minutes) is good for your immune system and is associated with fewer infections. Only prolonged heavy exertion or weeks of overtraining is counterproductive, so that is where the boundary lies.
Moderate exercise, meaning sessions of roughly up to 45 minutes, benefits your immune system. Several studies show that people who are regularly moderately active get fewer infections than people who barely move. This effect has been demonstrated most clearly in older adults and people with a chronic condition. Moderate exercise also has an anti-inflammatory effect: it influences signalling molecules in the blood that keep the immune response on track. That appears to be an important mechanism behind the broader health benefits of physical activity.
Intense, prolonged exertion reverses this picture. More than an hour and a half of high-intensity exercise temporarily suppresses several immune cells (such as white blood cells and lymphocytes). That dip lasts from three to twenty-four hours after the exertion. For occasional long training sessions this is not a major problem for most healthy people, but in elite athletes who train too hard for weeks on end the immune problems can persist. Respiratory infections are even one of the most frequently cited reasons for missed training days among this group.
Whether heavy exercise in itself raises the risk of infection is less certain. Sleep deprivation, stress, travel and nutritional deficiencies go hand in hand with the exercise itself during intensive training programmes. Disentangling those factors from the effect of exercise alone is difficult, and the debate on this point has not yet been settled.
In addition, several smaller studies suggest that even a single session of moderate exercise can improve the response to a vaccination in vulnerable groups. This evidence is still limited, but it fits the broader picture that moderate activity gives the immune system a boost.
Based on three sources (PMID 17303714, 32139352, 26477922), a combination of review articles and observational studies. No large randomised trials; causality for the infection outcome is associative, while for the immune effects it is probably causal.
Does too little sleep weaken your immune system?
Yes, too little sleep demonstrably weakens your immune system and increases the risk of infections and chronic inflammatory conditions. Seven to nine hours of sleep is the most commonly cited guideline, and vaccinations also work better when you are well rested.
Does your immune system really weaken as you get older?
Your immune system demonstrably weakens with age, but vaccinations remain worthwhile and a good diet can limit further decline.
How do I strengthen my weakening immune system?
You can partly support your immune system by correcting measured deficiencies in vitamins and minerals and by making use of vaccines specifically tailored for older adults. More far-reaching options such as experimental inhibitors are not yet safe enough for daily use outside of studies.
Does regular exercise help against that creeping chronic inflammation?
Regular, moderate exercise demonstrably lowers inflammatory markers such as CRP and IL-6; training too intensely can reverse that effect, so moderate exercise three to five times per week is the best-supported choice.
What does alcohol do to your immune system?
Chronic excessive alcohol use weakens your immune system on multiple fronts simultaneously and increases the risk of serious infections. Light to moderate drinking appears less harmful, but offers no demonstrable benefit for your immune system.
Does exercise help your immune system as you age?
Regular, moderate exercise helps your immune system by reducing smouldering inflammation. Suddenly training very hard without a gradual build-up can actually temporarily lower your immune defences.