Exercise immunity and susceptibility to infection a shaped relationship

How to boost your immune system - Harvard Health

exercise immunity and susceptibility to infection a shaped relationship

Exercise and risk of upper respiratory tract infection (URTI). ○ The J-shaped Curve. ○ The General Population: regular moderate exercise. is an S-shaped relationship between exercise load and risk of infections. To become state-of-the-art physique, including an immune system able to withstand. Exercise, Immunity, and Susceptibility to Infection: A J-Shaped Relationship? Shephard, Roy J.; Shek, Pang N. Physician and Sportsmedicine, v27 n6 p .

At present, only a few small longitudinal and cross-sectional studies most comparing athletes and nonathletes are available.

exercise immunity and susceptibility to infection a shaped relationship

Cross-sectional comparisons of human endurance athletes and nonathletes for NK cell activity, neutrophil function phagocytosis and oxidative burstand lymphocyte proliferative response T-cell function have provided interesting but somewhat inconsistent data. NK Cell Activity Cross-Sectional Studies The majority of cross-sectional studies support the finding of enhanced NK cell activity in athletes when compared with nonathletes, in both younger and older groups Nieman et al.

In one study, NK cell activity was 57 percent higher in experienced marathon runners compared with sedentary controls Nieman et al.

Not all studies, however, support the finding of a higher NK cell activity in athletes versus nonathletes Nieman et al. Prospective Studies Several prospective studies utilizing moderate endurance training regimens over 8 to 15 weeks have reported no significant elevation in NK cell activity relative to sedentary controls Baslund et al.

Together, these data imply that endurance exercise may have to be engaged in for a prolonged time period i. Neutrophil Function The cross-sectional data on neutrophil function are in contrast to those for NK cell activity both components of the innate immune system.

Instead, during periods of high-intensity training, neutrophil function has been reported to be suppressed in athletes.

This is especially apparent in the studies by Hack and coworkers and Baj coworkerswhere neutrophil function in athletes was similar to controls during periods of low training workloads but significantly suppressed during the summer months of intensive training.

Pyne and coworkersreported that elite swimmers undertaking intensive training had a significantly lower neutrophil oxidative activity at rest than did age- and sex-matched sedentary individuals and that function was further suppressed during periods of strenuous training prior to national-level competition. Because neutrophils are considered the body's best phagocyte, suppression of neutrophil function during periods of heavy training is probably a significant factor explaining the increased URTI risk among athletes.

These data may be the most important evidence to date linking risk of respiratory infection with athletic endeavor. Repeated cycles of heavy exertion may thus put the athletes at increased risk of URTI.

T-Cell Function Data on the mitogen-induced lymphocyte proliferative response generally a measure of T-cell function to athletic endeavor are less clear than for NK cells and neutrophils, but the data usually support no significant difference between athletes and nonathletes Nieman et al.

Interleukin IL -2 generation, however, was suppressed in the athletes versus controls during intensive training. These data contrast with that of Tvede and coworkers who found no difference between athletes and nonathletes during both low or high training periods.

Exercise, immunity, and susceptibility to infection: a j-shaped relationship?

Data from Japan also support enhanced T-cell function among trained elderly men versus untrained controls Shinkai et al. These data are interesting because T-cell function tends to diminish with age see section on " Exercise, Aging, and Immunity ". Other Measures of Immunity Other components of immunity have been less well studied among human athletes and nonathletes. Tomasi and coworkers reported that resting salivary IgA levels were lower in elite cross-country skiers than in age-matched controls, but this was not confirmed in a follow-up study of elite cyclists Mackinnon et al.

As reviewed by Mackinnon and Hooperthe secretory immune system of the mucosal tissues of the upper respiratory tract is considered the first barrier to colonization by pathogens, with IgA the major effector of host defense.

Secretory IgA inhibits attachment and replication of pathogens, preventing their entry into the body. Although several studies have shown that salivary IgA concentration decreases after a single bout of intense endurance exercise, further research is needed to determine the overall chronic effect. Practical Applications for Exercise Prescription These data support the concept that the innate immune system responds differentially to the chronic stress of intensive exercise, with NK cell activity tending to be enhanced while neutrophil function is suppressed especially during periods of heavy training.

The adaptive immune system, 3 in general, seems to be largely unaffected except perhaps in the highly trained elderly individualsalthough the research data at present are mixed. Further research is needed with larger groups of athletes to allow a more definitive comparison. Thus any positive effects on immunosurveillance and host protection that come with moderate exercise training are probably related to changes that occur during each exercise bout.

For athletes, periods of heavy training have been associated with suppression of neutrophil function. Neutrophils are an important component of 3 That part of the immune system that responds in a manner that is 1 highly specific for a particular pathogen and 2 increased in intensity with each successive encounter with that pathogen.

Athletes should be made aware of this potential problem and urged to avoid overtraining see " Practical Guidelines for Military Recruits and Athletes ". Exercise and Upper Respiratory Tract Infections Among elite athletes and their coaches, a common perception is that heavy exertion lowers resistance and is a predisposing factor to URTI.

There is also a common, contrasting belief among many individuals that regular exercise confers resistance against infection. For example, a survey of masters athletes ranging in age from 40 to 81 years showed that 76 percent perceived themselves to be less vulnerable to viral illnesses than their sedentary peers Shephard et al. Understanding the relationship between exercise and infection has potential implications for public health.

One important question is whether dietary supplements may help older people maintain a healthier immune system. Older people should discuss this question with a physician who is well versed in geriatric nutrition, because while some dietary supplementation may be beneficial for older people, even small changes can have serious repercussions in this age group. Diet and your immune system Like any fighting force, the immune system army marches on its stomach.

Healthy immune system warriors need good, regular nourishment. Scientists have long recognized that people who live in poverty and are malnourished are more vulnerable to infectious diseases. Whether the increased rate of disease is caused by malnutrition's effect on the immune system, however, is not certain.

There are still relatively few studies of the effects of nutrition on the immune system of humans, and even fewer studies that tie the effects of nutrition directly to the development versus the treatment of diseases. There is some evidence that various micronutrient deficiencies — for example, deficiencies of zinc, selenium, iron, copper, folic acid, and vitamins A, B6, C, and E — alter immune responses in animals, as measured in the test tube. However, the impact of these immune system changes on the health of animals is less clear, and the effect of similar deficiencies on the human immune response has yet to be assessed.

So what can you do? If you suspect your diet is not providing you with all your micronutrient needs — maybe, for instance, you don't like vegetables — taking a daily multivitamin and mineral supplement may bring other health benefits, beyond any possibly beneficial effects on the immune system. Taking megadoses of a single vitamin does not. More is not necessarily better. Improve immunity with herbs and supplements?

Walk into a store, and you will find bottles of pills and herbal preparations that claim to "support immunity" or otherwise boost the health of your immune system. Although some preparations have been found to alter some components of immune function, thus far there is no evidence that they actually bolster immunity to the point where you are better protected against infection and disease.

Demonstrating whether an herb — or any substance, for that matter — can enhance immunity is, as yet, a highly complicated matter. Scientists don't know, for example, whether an herb that seems to raise the levels of antibodies in the blood is actually doing anything beneficial for overall immunity.

Stress and immune function Modern medicine has come to appreciate the closely linked relationship of mind and body. A wide variety of maladies, including stomach upset, hives, and even heart disease, are linked to the effects of emotional stress. Despite the challenges, scientists are actively studying the relationship between stress and immune function. For one thing, stress is difficult to define.

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What may appear to be a stressful situation for one person is not for another. When people are exposed to situations they regard as stressful, it is difficult for them to measure how much stress they feel, and difficult for the scientist to know if a person's subjective impression of the amount of stress is accurate. The scientist can only measure things that may reflect stress, such as the number of times the heart beats each minute, but such measures also may reflect other factors.

Most scientists studying the relationship of stress and immune function, however, do not study a sudden, short-lived stressor; rather, they try to study more constant and frequent stressors known as chronic stress, such as that caused by relationships with family, friends, and co-workers, or sustained challenges to perform well at one's work. Some scientists are investigating whether ongoing stress takes a toll on the immune system. But it is hard to perform what scientists call "controlled experiments" in human beings.

In a controlled experiment, the scientist can change one and only one factor, such as the amount of a particular chemical, and then measure the effect of that change on some other measurable phenomenon, such as the amount of antibodies produced by a particular type of immune system cell when it is exposed to the chemical.

In a living animal, and especially in a human being, that kind of control is just not possible, since there are so many other things happening to the animal or person at the time that measurements are being taken. Despite these inevitable difficulties in measuring the relationship of stress to immunity, scientists are making progress.

Get your copy of Vitamins and Minerals About half of all Americans routinely take dietary supplements. The most common ones are multivitamin and multimineral supplements. This report explains the evidence behind the benefits and safety profiles of various vitamins and minerals. It also includes the recommended minimum and maximum amounts you should consume, as well as good food sources of each.

exercise immunity and susceptibility to infection a shaped relationship

Does being cold give you a weak immune system? Almost every mother has said it: So far, researchers who are studying this question think that normal exposure to moderate cold doesn't increase your susceptibility to infection. Most health experts agree that the reason winter is "cold and flu season" is not that people are cold, but that they spend more time indoors, in closer contact with other people who can pass on their germs.

But researchers remain interested in this question in different populations. Some experiments with mice suggest that cold exposure might reduce the ability to cope with infection. But what about humans? Scientists have dunked people in cold water and made others sit nude in subfreezing temperatures.

They've studied people who lived in Antarctica and those on expeditions in the Canadian Rockies. The results have been mixed.

Exercise and Immunity - FUTURELIFE®

For example, researchers documented an increase in upper respiratory infections in competitive cross-country skiers who exercise vigorously in the cold, but whether these infections are due to the cold or other factors — such as the intense exercise or the dryness of the air — is not known.

A group of Canadian researchers that has reviewed hundreds of medical studies on the subject and conducted some of its own research concludes that there's no need to worry about moderate cold exposure — it has no detrimental effect on the human immune system. Should you bundle up when it's cold outside? The answer is "yes" if you're uncomfortable, or if you're going to be outdoors for an extended period where such problems as frostbite and hypothermia are a risk.

But don't worry about immunity. Good or bad for immunity? Regular exercise is one of the pillars of healthy living. It improves cardiovascular health, lowers blood pressure, helps control body weight, and protects against a variety of diseases. But does it help to boost your immune system naturally and keep it healthy? Just like a healthy diet, exercise can contribute to general good health and therefore to a healthy immune system.

It may contribute even more directly by promoting good circulation, which allows the cells and substances of the immune system to move through the body freely and do their job efficiently. Some scientists are trying to take the next step to determine whether exercise directly affects a person's susceptibility to infection.

For example, some researchers are looking at whether extreme amounts of intensive exercise can cause athletes to get sick more often or somehow impairs their immune function. To do this sort of research, exercise scientists typically ask athletes to exercise intensively; the scientists test their blood and urine before and after the exercise to detect any changes in immune system components. While some changes have been recorded, immunologists do not yet know what these changes mean in terms of human immune response.

But these subjects are elite athletes undergoing intense physical exertion. What about moderate exercise for average people?