Medicinal Herbs and ADHD


Effects of Exercise Training on Immune Function and Implications for Nutrition Support

David C. Nieman, DrPH, FACSM | 2020

 Ask An Expert

We can start off with just a little bit about your background.

Dr. Nieman: I’m a biology professor and direct the Human Performance Laboratory here at the North Carolina Research Campus in Kannapolis, NC. My research area is nutrition, exercise, and how it affects the immune system. We use modern techniques like proteomics, metabolomics, and lipidomics to study the whole body system response to the nutritional or exercise intervention.

I’ve done a lot of work in the area of exercise, nutrition, and how both affect infection rates, mainly with the common cold because it is widespread. We showed that illness days are reduced by 45 percent if people walk briskly for 30 to 45 minutes on most days of the week during the winter or fall season when rhinoviruses, coronaviruses, and other upper respiratory tract infection viruses are circulating. Laboratory studies showed that moderate activity stimulates the immune system to do its job better. In other words, the immune system actually needs physical activity to do its job properly.

On the other hand, people can push exercise too far into a stress zone. For example, after running a competitive marathon race, there tends to be post-race downturn in immune function. This is transient and lasts about a day or so, but during this “open window” the immune system is not functioning properly. As a result, respiratory infection rates rise, especially during the one to two week period after a marathon race. We showed that after the Los Angeles marathon, which is in March every year, the odds of getting sick were six times higher in those who ran the race versus those who did not. The relationship between exercise and illness can be depicted in a “J curve,” with illness risk below normal with moderate activity but above normal after heavy exertion. Given these research findings, I recommend the avoidance of heavy exercise training if exposure to infection is high.

What is the main driving force behind the increased activity and improving the immune system? What does exercise do to cause the immune system to operate better?

Dr. Nieman: During a 30 to 45 minute bout of brisk walking, for example, muscular activity recruits immune cells from peripheral lymphoid tissues. When sitting, 98 percent of the immune cells are in the spleen, lymph nodes, and similar sites, similar to Marines in their home bases. With moderate physical activity, important types of immune cells are recruited into the bloodstream, just like Marines getting out of their bases. The immune cells circulate throughout the body, detecting and destroying viruses and bacteria, and then return back to the lymphoid tissue bases. With prolonged and intense exercise, immune cells are recruited into the circulation in high numbers but at a very high level of activation due to the physiological stress, muscle damage, inflammation, and oxidative stress. This is just like the Marines being out too long, running too hard, and pushing too much, leading to exhaustion and dysfunction. In general, moderate activity improves the circulation of immune cells that detect and destroy viruses and bacteria. But push the exercise too far into an overtraining stress zone, and immune dysfunction can occur.

Is this a novel type of research that’s showing this or has this been around and people just ignore it?

Dr. Nieman: The earliest studies date all the way back into the 1800s but the scientific area of exercise immunology really started with the HIV epidemic in the early- to mid-80s. That epidemic stimulated a lot of research on the linkage between exercise and immune function. We started the International Society of Exercise and Immunology (ISEI), and we meet every two years to review the latest research.

When you talk to most doctors and they diagnose you with the flu, they’ll tell you go home – rest – and it’ll get better. But that sounds like it’s opposite of what really you should be doing.

Dr. Nieman: There are two issues here: prevention and treatment. Regular exercise is great at helping people lower their odds of getting sick with infectious agents. But once you are sick, exercise is not recommended for treatment. you can’t use exercise to treat the common cold or the flu. In fact, we tell people you should totally rest until the symptoms go away. Or we have what we call the neck rule. If the symptoms are neck up, like just a runny, stuffy nose, you can probably go for a walk and that’s fine, but nothing severe.

When you have systemic illness, your whole body feels achy, and you have a fever. So the virus is throughout the body, not just neck up like the common cold. With the flu or similar systemic illnesses, complete rest is recommended. Animal studies indicate that if animals are forced to exercise hard when infected, mortality rates are higher, and the duration and severity of symptoms are worse. We can’t conduct these studies with human participants, but we feel the results are very applicable and that people should just rest if they are sick with something like the flu.

You also talked about the impact of diet on the immune system, so maybe you can mention a little bit about that.

Dr. Nieman: Some people, like warfighters and athletes, have to train hard, and we have investigated nutritional support strategies to help maintain immune function. Our data support negative immune changes after heavy exercise can be countered by ingesting a cup of blueberries each day or using carbohydrates like bananas or sports drinks during prolonged exercise. The immune cells have to have glucose to function properly, just like other cells in the body. If the athlete drains their body of carbohydrate with heavy exercise, they put the immune system in a red flag mode. This is because it’s like starvation, and the cells can’t do their job without fuel.

So we recommend that athletes and warfighters ingest carbohydrate before, during, and after they exercise. They shouldn’t exercise hard using water alone. We also recommend eating lots of fruits, especially berries that are rich in polyphenols. Polyphenols provide color in fruits, like the purple color in blueberries, the red color in pomegranates, and the orange color in oranges. These polyphenols are processed into molecules in the body that help regulate the immune system and maintain proper function. We weren’t really designed to really run marathons—definitely not a healthy pursuit. But for those who must exercise hard, ingest carbohydrates and polyphenols, and this nutrition support will help take the edge off the negative immune consequences.

And what about for the average person who’s not doing intensive exercise – what is the impact of exercise on them?

Dr. Nieman: Physical activities like regular brisk walking are very healthy and help the immune system do its job better. Our studies show that the number of illness days during the winter and fall are reduced 40 to 50 percent. At the same time, if you eat a lot of polyphenol-rich fruit like blueberries, additional support is provided to the immune system. We showed that people from the community eating three or more servings per day of fruit had a reduction in the number of days sick with the common cold.

So a good strategy is to exercise moderately for 30 to 60 minutes each day while eating lots of fruit and keeping mental stress under control. Our community study with 1000 people showed that this lifestyle approach greatly reduced the risk for getting sick with respiratory infections.

And do you think that those types of people who are in those situations also are impacted from other health conditions besides just things like colds and flu, but other things might be a problem for them or do you not have enough information to indicate that?

Dr. Nieman: We know that lean, fit individuals who eat a lot of fruit have less heart disease, diabetes, obesity, and many types of cancer. At the same time, cognitive function is improved and the odds of Alzheimer’s disease and senility is reduced. So a good lifestyle reduces the odds for common chronic diseases while at the same time supporting good immune function and reducing the risk for infectious illness. So there are both short term and long term benefits here.

Is there any difference between eating fruit that is organic versus non-organic?

Dr. Nieman: Most studies show very minor differences. What matters is eating lots of fruits and vegetables rich in polyphenols and fiber. Every indication is that the polyphenol content of produce in typical stores is very similar to what is found with organic fruits and vegetables. The pesticide residue on fruits and vegetables is too low to have a measurable impact on human health. People are overly worried about pesticide residue and the nutrient quality of the fruits and vegetables found in the store. This leads to low fruit and vegetable intake despite all of the research showing that five to nine servings per day is consistent with decreased disease risk and a longer life.

How does this relate to products that help support this in a patient’s diet or immune support?

Dr. Nieman: The average American only eats one serving of fruit and one serving of vegetable a day. That’s the national average despite recommendations for eating 5 to 9 servings a day. Despite all the public health efforts to get people to eat more fruits and vegetables during the last several decades, people have been resistant to changing their diets. They’re more open to consuming whole food extracts that contain many of these healthy polyphenols but do not have the dietary fiber found in the original fruit and vegetables.

Do you find that people can start taking the supplement and feel better and then realize that, hey, maybe I could do this in my diet?

Dr. Nieman: Our research with polyphenol supplements indicate they work just fine in supporting good immune function during physiological stress. We’ve used all kinds of extracts including those from green tea, blueberries and bilberries, and other plant sources.

When you talk to practitioners about this, what’s the key point that you want them to understand?

Dr. Nieman: Exercise is like medicine, and people will feel the benefits, both short and long term if they set aside 30 to 60 minutes a day. They can break it up, spread it out throughout the day. In fact, we’ve shown that nothing is more powerful than something like brisk walking on most days of the week. Exercise is the most important of all lifestyle habits for supporting immune function and stimulating immune cells to circulate throughout the body. Immune support can be further enhanced by getting high levels of polyphenols from fruits and vegetables and whole food extracts.

Do you know of any programs where corporations are actually pushing fruit for breaks rather than coffee breaks to help people consume more or is that too novel?

Dr. Nieman: There is much room here for innovation. For example, at soccer matches for children, fruit bowls could be supplied instead of sugar drinks and cookies. I think the kids would go for it, and hopefully public health action can be stimulated to this end. This will take education, legislation, and pro-active parents. We did this with cigarette smoking, and hopefully exercise and diet improvement can be the next target.

David C. Nieman, DrPH, FACSM, is a professor in the Department of Biology, College of Arts and Sciences, at Appalachian State University, and director of the Human Performance Lab at the North Carolina Research Campus (NCRC) in Kannapolis, NC. Dr. Nieman is a pioneer in the research area of exercise and nutrition immunology, and helped establish that 1) regular moderate exercise lowers upper respiratory tract infection rates while improving immunosurveillance, 2) heavy exertion increases infection rates while causing transient changes in immune function, and 3) that carbohydrate and flavonoid ingestion by athletes attenuates exercise-induced inflammation. Dr. Nieman’s current work is centered on investigating unique nutritional products as countermeasures to exercise- and obesity-induced immune dysfunction, inflammation, illness, and oxidative stress using a multi-omics approach.

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