The COVID-19 pandemic has all of us concerned – and rightly so.  COVID-19 has a case-fatality rate estimated between 2-4% (compared to <1% for seasonal influenza) and as high as 20% in those over 80 years oldthose with comorbidities are especially vulnerable1,2. We must all practice adequate social distancing, proper hand hygiene and general caution interacting with our fellow humans, particularly children (who often show few or mild symptoms), the elderly and those with pre-existing health conditions. 

In the midst of the global conversation around these essential measures, the role of Lifestyle Medicine seems to have been mentioned infrequently, yet it is one of the most important areas we can focus on, for two reasons. First, there is evidence that a host of lifestyle factors can improve people’s overall health, specifically the function of our immune systems, cardiovascular systems, diabetes control and respiratory health. Hence, improvements in lifestyle factors may assist in preventing progression of infections to severe or critical disease. Second, the presence of COVID-19 does not mean the absence of the acute and chronic diseases that are already so prevalent in our society. The health system must still manage these disorders; but now it has far less resources to do so. Hence, the best thing we can all be doing is taking care of ourselves through optimised lifestyles, thereby reducing the burden on the healthcare system and allowing our limited resources to go where they are needed most. 

Cigarettes and alcohol 

Cigarette smoking has long been known to increase the risk of microbial infection. Smoking has a deleterious impact on our ability to fight infection, by disrupting the mucociliary escalator, immune cell function and weakening the epithelia in the lower airways, resulting in a greater likelihood of severe respiratory syndromes, and a slowed and less complete recovery. Indeed, the greatest known risk factor in the progression of COVID-19 is tobacco smoking: the risk of death is 14 times greater in those with a history of smoking compared to those without3. While quitting smoking is never an easy undertaking, there really is no better time than to quit than now. 

And while only 14% of Australians smoke, most of us consume alcohol on a regular basis. There is some evidence to suggest that moderate consumption of alcohol in healthy adults, in particular wine and beer, has little to no effect on the immune system, with some studies even showing beneficial effects4. Moderation, in the form of less than 2 standard drinks per day, is encouraged, and if you have any sign of flu-like symptoms, abstinence remains the safest option. 

Nutrition

The foods we consume on a daily basis have a profound impact on our health. Our daily nutrition is well-established as a leading risk factor in the development of obesity, cardiovascular disease and type 2 diabetes. The typical ‘Western diet’, awash in refined sugars, excess salt, white flour, processed meats, purified animal fats and food additives, contains low levels of dietary fibre, vitamins, minerals and antioxidants5; this diet promotes caloric excess and obesity, which impair immune function6. Eating in this way can impact immunity through a variety of mechanisms, including a reduced ability to respond to invading pathogens7, partially through having fewer and less potent white blood cells8,9. 

While obesity remains a great public health concern in Australia, diets low in whole foods can produce nutrient deficiencies. Deficiencies in micronutrients including essential amino acids, folic acid, vitamins A, B6, B12, C and E, copper, iron and selenium can impair virtually all immune functions, making us more susceptible to infectious agents10. Consumption of these micronutrients at or above currently recommended levels is thus essential for the optimised function of our immune systems11. Incorporating more fresh fruits, vegetables, nuts, seeds, whole grains and perhaps some lean fish and poultry, while minimising the intake of processed foods, remains sound dietary advice. Such diets also promote a healthy gut microbiome12, which can enhance our defence mechanisms against invading pathogens13While taking a deep dive into various dietary patterns and the claims around so-called ‘superfoods’ is beyond the scope of this article, we make a notable exception for the kiwifruit. It contains vitamin C, carotenoids, polyphenols and fibre, and has – in some intervention studies – been shown to reduce the incidence and severity of upper respiratory tract infections14. 

It is also worth noting the effect of diet on asthmatics, a population particularly at risk in the current moment. Asthmatics following a typical Western diet are at a higher risk of exacerbations – which can be triggered by viral infection – than those following a diet rich in fruit and vegetables.  In a three-month window, asthmatics who consumed 7 servings of fruits and vegetables a day had a 20% exacerbation rate, compared with 40% in those on a Western diet with just three servings of fruits and vegetables each day15.  Evidence from a randomised controlled trial suggests that these drastic improvements in exacerbation rates can be achieved after just fourteen days of increased fruit and vegetable consumption16. 

Finally, on a very interesting (and frightening) note, genetic studies using the coxsackievirus and influenza virus – two vastly different pathogens – have shown that virulence-enhancing mutations predictably occur when nutritionally compromised hosts are infected, particularly those with a deficiency in selenium and an excess in iron17. The benefits of eating well, then, extend beyond our individual responses and into the realm of the greater global community of humankind. 

Exercise

Moderate exercise training, such as 30 minutes of elevated heart rate, five times per week, has been shown to increase immunity and reduce both the incidence and number of symptoms days in upper respiratory tract infections. While the greatest effect is seen after 3 months of near-daily moderate exercise, an enhanced circulation of a variety of immune cells occurs during each individual exercise session and can persist for up to 3 hours post-exercise18. Encouragingly, those who are currently sedentary, and the elderly in particular, stand to gain the greatest benefits in immune function, as sedentary behaviour is associated with immunosenescence and increased infection risk in ageing individuals19. 

Since most gyms, pools and other popular exercise facilities are either a) closed, or b) petri dishes for the spread of coronavirus, the COVID-19 pandemic represents an excellent opportunity to partake in outdoor physical activity, where effective social distancing can still be practiced. With 30% of Australian adults currently deficient in vitamin D, getting some sunlight, exercise and escaping your work-from-home setup will enhance vitamin D production, which is associated with a decreased risk of respiratory infections20. Vitamin D has been shown to stimulate monocyte proliferation and the production of antimicrobial peptides, which enhance the elimination of invading viruses21. Importantly, vitamin D levels have been inversely associated with clinical markers of asthma, as well as severity and exacerbations22,23. 

Better yet, if you are able to escape the city for a few hours, this may also have a positive benefit on your immune system. A series of studies performed in Japan investigated the effect of Shinrinyokuor ‘forest-bathing’, where healthy male and female volunteers visited the forest for several days. Following the trip, immune assays were performed, revealing increased natural killer cell activity and numbers, which persisted for up to 30 days24. Though studies on the effect of shorter duration nature exposure on immune function have not been performed, given the well-established benefits of nature exposure for mental health25,26, essential in times of social isolation, it stands to reason that there is – at bare minimum – no harm in exposing oneself to natural landscapes, particularly if there are immune-boosting effects. Note that, at the time of writing, camping sites and most holiday destinations have now been closed, so exposing oneself to the natural world for more than a few hours is, at present, not possible. 

Sleep

If one takes the time to exercise and expose themselves to plenty of daylight, it is almost a certainty that their quality of sleep will improve. At present, over a third of Australian adults are getting inadequate sleep27, which could be impairing our immune system’s ability to recover and fight off infections. Sleep is well-known to bolster the immune response; most immune cells’ response to an immune challenge peak during the night28. Similarly, poor sleep quality and duration impair our ability to respond to both viral and bacterial infections29. 

Stress (reduction)

Stress seems to be synonymous with modern life. And for most of us, stress levels have been rising linearly with the cases of COVID-19 (evident by the dwindling supplies of canned vegetables, pasta and toilet paper in supermarket aisles). Stress, via the action of various hormones (e.g. cortisol), is detrimental to the functioning of the immune system, affecting natural killer cell activity, lymphocyte efficacy and proliferation and antibody production30. Overall, stress has been shown to increase susceptibility to, and severity of, infection31, with the risk of upper respiratory viral infection increasing with increased cortisol levels32. 

Also rising with the curve of coronavirus is social media use, which has exploded since COVID-19 entered our collective consciousness33. We know that increased social media use is correlated with increased anxiety and stress34,35, which do our immune systems no good. Though keeping up to date with the latest coronavirus updates is important, keeping interaction with social media within reasonable limits will be beneficial to both your mental and physical health. 

With rising stress levels being detrimental to immune function, taking action to reduce our stress levels is essential. Consider taking some time away from it all and incorporating meditation a part of your daily routine. Evidence supports meditation for improved mental health36, and some evidence exists that it may create positive changes in immunity37. While the evidence that meditation enhances immunity is not conclusive, the negative side effects of meditation are non-existent for the general population, and many people find that it creates more time than it takes. 

Social support

Finally, while it may be difficult to catch up with friends and family when practicing social distancing, staying connected is important for maintaining mental and physical health. Social connection provides an immune-boosting benefit, with a meta-analysis of 81 studies finding a strong link between social support and improved immune function38. Improved social connection has been associated with a greater antibody response following influenza vaccination39,40 and experimental data shows that individuals with more diverse social networks were less likely to develop symptoms following inoculation with a common cold rhinovirus41. 

While building a strong social network is not a task one can accomplish in a short period of time (especially now), it underlines the importance of maintaining contact with friends and family, be it via phone call or video chat, during this period of social distancing. 

For many of us, the COVID-19 pandemic has pushed us into unprecedented times. As individuals within the global community, we can each make a substantial contribution to steer the outcome of this disease in a more positive direction. Government policies, good hygiene and social distancing will slow the transmission of disease from person to person. Looking after ourselves, by making small, positive changes to our lifestyles, can strengthen our immune systems and result in a shorter, less severe bout of illness, should any of us be infected. Individually and together, we can slow the spread of COVID-19, reduce the burden on the healthcare system and emerge from this pandemic stronger, wiser and more united than before. This is crucial for the health and longevity of ourselves and our societies, and so we are better prepared for the next one.  

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This article has been re-published with permission from its original authors, Mark Blencowe and ASLM President, Dr Sam Manger. It was originally published on The GP Show

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