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Arm Yourself with Knowledge against Cold and Flu!
Regular Exercise Boosts Your Immune System

Nobuhiko Eda
Assistant Professor, Faculty of Sport Sciences, Waseda University

Cancer is the leading cause of death among senior citizens in Japan followed by heart disease. Do you know what comes next? The answer is pneumonia (Figure 1). Senior citizens are susceptible to both aspiration pneumonia, caused by inhaling foreign substances, and hospital-acquired pneumonia, which develops after being infected by a cold or flu virus. Since both types tend to get worse, prevention is critical. Needless to say, cold and flu infection is something you definitely want to avoid even if you are not old. Although it is well known that wearing a mask, washing your hands frequently, gargling frequently, and keeping indoor humidity at an appropriate level are helpful, it is still impossible to completely prevent viruses from entering your body.

1. Cause of death in Japan (prepared by the author based on government references1)

Archenemy of Colds and Flu: Immunoglobulin (Ig)

The immune system is our last resort. This article focuses on the adaptive immune system, which plays an important role in preventing cold and flu infection. The adaptive immune system has five types of antibodies, called immunoglobulin (IgM, IgD, IgG, IgE, and IgA). When a pathogen such as a germ or virus enters your body, antibodies bind to the germ or virus to prevent membrane penetration, bind to a virus or toxin to suppress its activity (neutralization), or bind to a pathogen to be engulfed by white blood cells such as macrophages (opsonization2). It has been reported that, among the various types of immunoglobulins, a low level of immunoglobulin A (SIgA) in saliva makes individuals more susceptible to colds and flu (Figure 2).

Figure 2. Functions of immunoglobulin A inside the mouth

Regular Moderate Exercise Increases Immunoglobulin

Recent studies have shown that moderate exercise can increase immunoglobulin levels. For example, 45-minutes of low-intensity walking five times a week for 15 weeks resulted in increased levels of IgG, IgA, and IgM in the blood3. Another study reported that 12 months of rowing exercise increased the blood IgD level4. Also, our study group has reported that, when elderly participants who did not exercise on a regular basis engaged in light strength training and moderate aerobic exercises twice a week, the SIgA level in their saliva increased (Figure 3).

Figure 3. Level of SIgA in saliva with continued exercise (based on reference5 data)

Increased Daily Activity Can Also Boost the Immune System

In a study of the relationship between daily physical activity level of older people (average age 70) and the SIgA level in their saliva, those who maintained a moderate level of physical activity (7,000 steps per day) showed a higher SIgA level in their saliva than those who had a lower level of physical activity (3,000 steps per day)6. This means that engaging in an adequate amount of walking on a daily basis can help people maintain a stronger immune system. It is nice to know that an easy activity like walking can help seniors and others who do not exercise regularly.

Does Exercise Impact the Effectiveness of Vaccines?

Do you get a flu vaccine every year? Daily physical activity level has been reported to influence the level of immune response to a vaccine. In a study of 56 middle-aged and elderly participants (62 or older), those who did high-intensity exercises for 20 minutes or more at least three times a week had higher blood IgG and IgM antibody levels in response to a flu vaccine than those who did low to mild intensity exercise7. Therefore, daily physical activity at relatively high intensity improves the effectiveness of vaccines, making individuals less susceptible to the flu virus. Exercising kills two birds with one stone: It not only boosts the immune system but also improves the effectiveness of vaccines.

Do Exercise and Sweating Help Recover From a Cold Faster?

This is a common belief, but is it true? When you have a cold, it is not the virus that raises the body temperature. It is the immune cells. Using a substance called cytokine, they order the brain to raise the body temperature. Cold viruses are said to reproduce best between 33 and 35℃ and stop multiplying at 37℃ or higher. The body temperature increases as a self defense response. Having said that, is exercise that raises the body temperature good for a cold?

Some studies have reported that low-intensity exercise temporarily boosts the immune system. In one study, after a 45-minute walking exercise, participants’ blood IgG, IgA, and IgM levels temporarily increased8. Also, our studies found increased levels of SIgA9 and defensin10, an antimicrobial peptide, immediately after 90 minutes of yoga (Figure 4). Since increased body temperature suppresses virus growth and low-intensity exercise such as walking and yoga temporarily boosts the immune system, it is possible that exercising can help individuals get over a cold faster. In fact, in America many people try to get over a cold by going for a light jog or walking once the initial symptoms appear.

Figure 4. Effect of yoga exercise on the levels of SIgA and defensin (based on reference data 9,10)

Note, however, that there is not sufficient scientific grounds to support this theory because making cold patients engage in exercise for research is risky and unethical. Furthermore, high-intensity exercise is known to decrease the immune system. It is quite possible that heat dissipation by sweating and exhaustion due to exercising when infected with a virus may aggravate cold symptoms. For this reason, instead of exercising after catching a cold, I believe the best we can do is to engage in mild regular exercise and maintain a high immune system level.

References

^ 1) Ministry of Health, Labour and Welfare "Vital Statistics". 2014.
^ 2) Eda, N. and Akama, T. "Undo to meneki – 5) Menekiguroburin" ["Exercise and immune system - 5) Immunoglobulin"]. Chapter 16. Nyu Undo Seirigaku (II) [New Sport Physiology (II)]. Miharu Miyamura (Ed.) Tokyo. Medical Book Publication Department, Shinko Trading Company. pp. 399-408, 2015.
^ 3) Nehlsen-Cannarella, S.L. et al. “The effects of moderate exercise training on immune response”. Medicine & Science in Sports & Exercise 23: 64-70, 1991.
^ 4) Petibois, C. et al. “The biological and metabolic adaptations to 12 months training in elite rowers”. International Journal of Sports Medicine. 24: 36-42, 2003.
^ 5) Akama, T. et al. "Yonju-ni kagetsukan no undo keizoku ni yoru chu-konennsha no daeki bunpitsugata imyunoguroburin A no henka" ["Change of salivary secretory IgA by 42 months exercise training in elderly persons"]. Sport Science Research. 2: 122-127, 2005.
^ 6) Shimizu, K. et al. “Effect of free-living daily physical activity on salivary secretory IgA in elderly”. Medicine & Science in Sports & Exercise. 39: 593-598, 2007.
^ 7) Kohut, M.L. et al. “Exercise and psychosocial factors modulate immunity to influenza vaccine in elderly individuals”. Journals of Gerontology A: Biological Sciences and Medical Sciences. 57: 557-562, 2002.
^ 8) Nieman, D.C. et al. “The effects of acute and chronic exercise of immunoglobulins”. Sports Medicine. 11: 183-201, 1991.
^ 9) Eda, N. et al. “A study on yoga stretching for improving salivary immune function and mental stress in middle-aged and older adults”. Journal of Sports Science and Medicine. (submitted)
^ 10) Eda, N. et al. “Effects of yoga exercise on salivary beta-defensin 2”. European Journal of Applied Physiology. 113: 2621-2627, 2013.

Nobuhiko Eda
Assistant Professor, Faculty of Sport Sciences, Waseda University

[Profile]
Born December 25, 1985, Ushiku City, Ibaraki, Japan

[Education]
2013 Ph.D (Sport Sciences), Waseda University
2010 Master of Sport Sciences, Waseda University
2008 Bachelor of Science, School of Sport Sciences, Waseda University

[Career]
2015-present Assistant Professor, Faculty of Sport Sciences, Waseda University
2013-2015 Assistant, Faculty of Sport Sciences, Waseda University
2012-present Instructor, Physical Education, Tokyo City University
2010-present Yoga instructor, Tsukuba City Council of Social Welfare

[Publications and research achievements]
1. Eda, N, et al. "Koukyodo jikyuusei undo ga hifu no butsuriteki baria ni oyobosu eikyo" ["Effects of high-intensity endurance exercise on the epidermal physical barrier"]. Sport Science Research. 9: 319-329, 2012.
2. Eda, N. et al. “Effects of high-intensity endurance exercise on epidermal barriers against microbial invasion”. Journal of Sports Science and Medicine. 12(1): 44-51, 2013.
3. Eda, N. et al. “Altered secretory immunoglobulin A on skin surface after intensive exercise”. Journal of Strength and Conditioning Research. 27(9): 2581-2587, 2013.
4. Eda, N. et al. “Effects of yoga exercise on salivary beta-defensin 2”. European Journal of Applied Physiology. 113: 2621-2627, 2013.
5. Eda, N. “Yoga has beneficial effects on patients with chronic diseases and improves immune functions”. Journal of Clinical Research & Bioethics. 5(5), 197: 1-3, 2014.
6. Eda, N. et al. “A study of bacterial growth on the skin surface after a basketball game”. Clinical Case Reports and Reviews. 1(11): 279-282, 2015.
7. Eda, N. and Akama, T. "Undo to meneki – 5) Imyunoguroburin" ["Exercise and immune system - 5) Immunoglobulin"]. Chapter 16. Nu Undo Seirigaku (II) [New Sport Physiology (II)]. Miharu Miyamura (Ed.) Tokyo. Medical Book Publication Department, Shinko Trading Company. pp. 399-408, 2015.