BODY WORK: How Running Can Boost Your Immune System

Running has some amazing benefits in terms of resistance to infection and certain cancers. People who run, or exercise aerobically, at a moderate level experience fewer days of sickness from the common cold and other upper respiratory tract infections (URTI). What’s more, less competitive runners following lower-key exercise regimens have enhanced immune reactions to infection. Many studies indicate that exercising at a medium intensity level reduces our risk of infection over the long term. How does this happen?

– Light or moderate running boosts our body’s natural immune system by circulating protective cells through the body faster, to attack and eliminate bacteria, viruses and fungi.

– Another theory holds that the increase in body temperature when we run may inhibit the growth of bacteria, thus reducing its foothold in the body.

– Some exercise scientists believe that regular running helps rid the lungs of airborne bacteria and viruses that cause URTI, while others say exercise causes the loss of carcinogens through increased sweat and urine loss.

– Active people also experience lower rates of colon cancer and breast cancer. Researchers think moderate exercise boosts the body’s immune system, attacking malignancies that have viral origin.

Don’t overdo it

Overtraining can suppress normal immune function, so it’s important to get the right balance of frequency, intensity and duration of running or general fitness workouts. Overtrained runners at all levels have been shown to experience impaired immune systems, to the extent that they suffer from a higher number of upper respiratory tract infections (URTI) than untrained people.

URTI is also elevated following competitive endurance races such as marathons. And it appears that the longer the endurance event, the harder the athlete’s immune system is hit. According to research, there’s an “open window” of altered immunity, lasting from three to 72 hours after you run hard and for longer than 90 minutes. In this time, infectious microbes, viruses and bacteria may overcome your body’s natural defences, depending on your natural state of immunity at the time.

If you train hard but within your limits, your URTI risk is typically unaltered, but there is a relationship between how much and how hard you exercise and your chances of getting an infection. Exercise scientists have proposed a J-shaped curve theory to explain this interrelationship between exercise and infection. This curve shows that as you extend yourself into protracted, higher intensity training, your chances of contracting infection rises almost exponentially, compared to a person training at a moderate level.

Drinking carbohydrate solutions during and after endurance exercise boosts the immune system. Taking in about one litre of sports drink per hour has been shown to lower blood cortisol and epinephrine levels, reduce adverse changes in blood immune cells and lower anti-inflammatory cytokine levels.

Tips for a strong immune system:

– Use carbohydrate drinks before, during and after running events or during very heavy exercise sessions. The recommended dosage is 30 to 60 grams of carbohydrate during exercise. This will lower the impact of the stress hormones on your immune system.

– Eat a well-balanced diet to keep vitamin and mineral levels in the body at optimal levels. Important vitamins and minerals that have the greatest impact on immune function are: vitamins A, E, B6, B12, folate, essential fatty acids, the amino acids glutamine, arginine, and L-carnitine. No research has conclusively shown that ingesting these in supplement form reduces URTI, but taking them in safe amounts will not do any harm, either.

– Avoid large crowds of people for 1-2 weeks after you finish a marathon or ultramarathon. You’re more susceptible to URTI during this time.

– Wash your hands with warm soapy water and minimize hand-to-eye and hand-to-nose contact, especially during cold and flu season.

– Do not exercise in a group setting if you have URTI, to avoid spreading it to others.

– Get adequate sleep on a regular schedule. Sleep disruption has been linked to lowered immunity.

– Keep your life stressors to a minimum, as high stress levels have been linked to URTI.

What to do if you contract a URTI?

– Mild to moderate running when sick with URTI does not appear to be harmful. But with symptoms of fever, extreme tiredness, muscle aches and swollen lymph glands, wait 2-4 weeks before resuming your running program.

– Avoid prolonged, exhaustive exercise during all stages of the common cold, regardless of symptoms.

Roy Stevenson teaches exercise science at Seattle University in Washington State and has coached hundreds of competitive and recreational runners.