30 minutes of exercise a day is enough to strengthen immune system responses to viruses and infection
Viruses and bacteria surround us all the time. They live inside us, making what is known as our microbiome, and also circle around us like an unseen cloud wherever we go. Some of these germs are airborne, some stay on surfaces we touch, others live in the food we eat. This process is completely uncontrollable by us, as these organisms are so minuscule that safeguarding against them most often goes beyond our abilities (unless we are placed in a sterile lab wearing sterile protective gear).
As I’m writing this, COVID-19 pandemic is well under way. China has had their quarantine time and is slowly coming back to normal life, however, most of Europe, North America and some parts of Middle East and Asia remain on lockdown orders.
There is not much we can personally do in order to stop the virus getting to us. By some experts’ forecasts, about 80% of the world’s population will get it. The actual life of this strain may likely take up to 6-12 months to finally go through the world's population and subside in infecting large masses of people.
While we are all trying to implement the best hygiene and social distancing measures, it is important to know the difference between doing our best to minimise the risk of the virus getting to us and mitigating its effect on our body once we have it.
Controlling the virus is rather out of our scope, but controlling the host (our body) where it can land is quite achievable for most of us. And hence the difference to whether we will have mild symptoms or a full-blown illness is in our individual immune system’s response.
There are a number of factors that influence how well our immune system works, among them our genetic predisposition, diet, stress, smoking, sleep and physical activity.
Research into the relationship between exercise and immune system functioning has been going on since the beginning of last century. There are studies dating back to 1900s when scientists aimed to investigate the dose and duration of such factors as the intensity of exercise, rest, recovery and sleep during viral and bacterial infections.
A vast number of studies to-date show that exercise promotes re-circulation of key immune cells, making the body to activate an anti-inflammatory and antioxidant state through multiple mechanisms.
When we engage in moderate or intense exercise, we induce a temporary level of stress on the body, with acute inflammation in the tissues. In order to help cure this inflammation, the body increases a number of inflammation-related biomarkers, such as white blood cells, a variety of specific proteins and cytokines (these are substances that are secreted by the cells in the immune system to help other cells). While all these processes take place, the cells of the immune system must be able to grow and propagate in order to produce these specific substances. Such activation of the immune system is accompanied by high demands on oxygen and means that the immune cells must engage in metabolic reprogramming just to produce enough energy to fuel these demands. It is believed that the degree to which the immune cells are activated depends on the overall exercise workload.
One of the most prominent researchers in the field of exercise and immunity is David Nieman - Professor of Health and Exercise Science at Appalachian State University and Director of the Human Performance Labs, North Carolina Research Campus. Last year Nieman published a paper in the Journal of Health and Sport Science, where he and his colleagues reviewed research on the relationship between exercise and immunity from the beginning of last century to date.
According to Nieman, 30-60 minutes of moderate to vigorous exercise 5 times a week serves as the best protection for our immune system. Interestingly, having analysed data of people who regularly walk or run, he came to the conclusion that the type of the aerobic exercise doesn’t play a difference. Both walking and running under 60 minutes trigger enough anti-pathogen activity and a heightened level of immune defence substances (such as immunoglobulins, anti-inflammatory cytokines, neutrophils, T cells, etc.) to play a critical role in the immune defence activity.
"Each bout of moderate physical activity promotes improved but transient immunosurveillance and, when repeated on a regular basis, confers multiple health benefits including decreased illness incidence and dampened systemic inflammation", - says Nieman.
Furthermore, a number of randomised clinical studies, conducted between 8 weeks to 1 year, show that regular moderate exercise is preventative in both the occurrence as well as the severity of upper respiratory tract infections, URTIs. The duration of days with an URTI was 43% lower in people who engaged in aerobic exercise on average 5 or more days per week, compared with those who were predominantly sedentary.
The protective mechanisms of exercise are especially important for the elderly. Many elderly people have a weakened immune system due to two factors, the first is a decreasing number of T cells (which are produced in smaller quantities as we age due to the shrinking thymus gland) and the diet which often has deficiencies in macro and micro nutrients. As appetite declines with age, an elderly person doesn’t have as much hunger, thus often lacking key nutrients in the diet. But with regular exercise, in the long term, people can slow down the changes that happen to the immune system during the ageing process.
The evidence from both randomised clinical studies and epidemiologic studies strongly points to the role of exercise in strengthening the immune system. Regular moderate and intense exercise between 30-60 minutes long triggers a set of mechanisms in the immune system that protect against viral and infectious diseases, such as the flu and pneumonia.