Exercise can boost our immune system by so much that we can reduce the number of symptom

days by 25 to 50 percent.

Imagine if there was some drug that could do that, it would rake in billions, whereas

exercise is free and tends to only

have good side effects. It doesn't even take much of a workout to get results. Studies find

that if you let kids run around for just six minutes, the levels of immune cells circulating

their blood can increase by 50% as they pour from the bone marrow and redeploy

throughout the body.

Even moderate exercise can also boost IGA production, protective antibodies that coat

all of our moist membranes.

Compared to a sedentary control group, those who performed aerobic exercises for 30 minutes,

three times a week, for 12 weeks,

had a 50% increase in levels of IGA in their saliva and reported significantly fewer flu-related

symptoms.

Salivary IGA levels are associated with lower overall mortality risk over time, particularly

cancer mortality, perhaps as a proxy for immune

function more generally, and you can boost those levels with exercise.

Exercise may also boost the activity of natural killer cells, or immune soldiers

that focus on eliminating both tumor cells and virus-infected cells. Here are five different types of cancer growing in a petri dish,

mostly leukemia and lymphomas, draw blood from people

and drip on some of their natural killer cells into the dish,

and they start killing off the cancer cells.

...