63) and may even motivate you to eat healthfully (67), both of which help keep your immune system young and strong.While strength training, balance, and flexibility exercises are critical for slowing down the aging process and keeping you young and healthy, studies show that aerobic exercise offers the most immune-boosting effects. Exercise can help shore up your immune system in the short term and over the long haul, providing extra protection against infection and disease as your body’s natural defenses begin to decline. For instance, immediately after a group of women completed a thirty-minute walking workout, researchers noted that several measures of their immune function improved, including increased counts of germ-fighting white blood cells and natural killer cells and reduced markers of inflammation, according to a 2005 study in Medicine and Science in Sports and Exercise.
Several studies have shown that working out regularly provides ongoing support for the immune system as well, including a 2005 study in the journal Neuroendocrinology Letters that found consistent, moderate exercise increases levels of immunoglobulins, antibodies in your blood that fight off illness. And other research indicates that exercise increases the effectiveness of vaccines, which is increasingly important as you get older, since an aging immune system is less responsive to vaccination. Previously sedentary older adults who exercised regularly after they received a flu shot showed a significant increase in vaccine-related protection against the flu as much as twenty-four weeks later, according to a 2009 study in the Journal of the American Geriatrics Society. Not only that, but they also slept better and, when they did get sick, had less severe respiratory tract infections than nonexercisers throughout the entire cold and flu season.
Research shows that thirty to forty-five minutes of moderate exercise on most days of the week will strengthen your immune defenses. A 2006 study in the American Journal of Medicine found that women who did forty-five minutes of moderate-intensity exercise five days per week for a year had increasingly improved immunity, to the point that by the end of the study they were three times less likely to catch a cold than those assigned to forty-five minutes of once-weekly stretching sessions.
The calories you burn through aerobic exercise also help you stave off obesity, which reduces immunity by aging the thymus system and slowing its production of T cells, a type of white blood cell. In addition, regular exercise helps you sleep better (63) and may even motivate you to eat healthfully (67), both of which help keep your immune system young and strong.
Adding high-intensity intervals to your exercise routine can help you increase speed and endurance and burn more calories in less time (94). However, research shows that this and other intense or prolonged exercise, such as training for a race, can actually suppress your immune system. For example, a 2008 review of studies in the Clinical Journal of Sports Medicine noted that particularly strenuous exercise may diminish activity of natural killer cells. A 2007 study in the European Journal of Applied Physiology found that high-intensity sessions can decrease neutrophils, a kind of white blood cell, and raise levels of interleukin-6, a marker of inflammation. You’ll see the most dramatic decline in immunity when exercise is continuous, prolonged, of moderate to high intensity, and performed without eating or drinking, noted U.K. researchers in a 2006 study.
But that doesn’t mean you should avoid high-intensity training if you enjoy it, experts say. Eating healthfully (including plenty of protein and carbohydrates), plus maintaining other immune-supporting habits such as getting enough sleep and managing stress go a long way to keeping you healthy and infection-free. If you exercise for more than ninety minutes, be sure to consume carbohydrates (such as a sports drink) during your workout to counteract the rise in stress hormones and minimize immune system suppression, suggests a 2008 study in Nutrition Reviews. The researchers also note that supplementing with antioxidants such as quercetin (a plant compound found in tea, fruits, and vegetables) and curcumin (a component of the curry spice turmeric) might help counteract the stress of strenuous exercise and restore white blood cell function. A small study reported immunity improvements in endurance cyclists taking 1,000 milligrams of quercetin supplements daily for three weeks before and during long bouts of exercise. More research is needed to determine the best postexercise dose of curcumin, though regular dietary intake may be enough—even small amounts show antioxidant action and other benefits (26).