Aside from the health-supportive ingredients and nutrients covered in prior posts, there are a few lifestyle choices that can also keep our immune systems functioning optimally and reduce the germs in our homes as we shelter in place, and a few that might be inadvertently sabotaging your efforts.
Exercise: enough, not too much
It might seem hard right now with all the restrictions in place, but getting enough physical activity is important for keeping the immune system functioning well (1). The relatively new field of ‘exercise immunology’ studies the ways in which activity keeps our immune systems strong (or not), finding that engaging in moderate exercise temporarily improves its defensive activity and decreases systemic inflammation. The old saying “everything in moderation” applies here: moderate intensity exercise for less than 60 minutes produces favorable changes, but more intense exercise for prolonged periods actually has the opposite effect, resulting in a temporary suppression of the immune system and increased inflammation. So, while it is a good idea to get out for a walk every day (30-45 mins is ideal), now is not the time to be running personal marathons!
Super-fit endurance runners actually have a higher risk of upper respiratory tract infections (URTIs), particularly if they aren’t getting enough sleep or are dealing with other stresses: while moderate exercise reduces susceptibility to URTIs by half, heavy exertion increases risk by up to six times. The right nutrition can counteract some of the inflammatory effects of prolonged exercise: getting enough carbohydrates during endurance activities (30-60 grams per hour) helps, and if these carbs are in the form of food (e.g. bananas, raisins, dates) rather than hydration beverages (e.g. Gatorade), they also deliver polyphenols and other plant compounds which may have further anti-inflammatory effects (2).
The Great Outdoors
Even if you are inactive, being outside in nature (or even inside with a good view) can reduce stress and improve overall health. A thorough review of the literature recently concluded that exposure to green space significantly reduces blood pressure, heart rate and cortisol levels (3), suggesting that adding greenery to urban neighborhoods could improve the health of those communities. As for how nature has such a positive effect on health, it looks like there are multiple mechanisms at play: plants give off antimicrobial compounds called phytoncides (essential oils) which reduce blood pressure and improve immune function, and the air in mountainous and wooded areas, as well as near moving water, contains higher levels of negative air ions that have been shown to reduce depression. Natural environments also contain microbes shown to improve human immune function and boost serotonin levels (4), and all of the sensory information (sounds, sights and scents) can also calm our nervous systems, activating the parasympathetic mode (the opposite of ‘fight or flight’).
Being in wooded areas specifically can stimulate immune cell activity (5). The Japanese have long-enjoyed the benefits of ‘forest bathing’ (AKA shinrin-yoku); their research shows that spending quality time in the woods increases the immune system’s level of natural killer cells (6) as well as reducing blood pressure and other inflammatory markers. The key to forest bathing is to take a peaceful, mindful walk in the woods and soak up the environment with all of your senses (rather than going for a vigorous hike, listening to music, or chatting with friends en route).
Fresh Air & Sunshine
When you are inside the house (which, let’s face it, is probably most of the time right now), you can still enjoy some of the benefits of nature. Opening up the windows allows some of nature’s sounds, sights and scents in, as well as inviting in fresh air. The World Health Organization and the US government recommend keeping windows open to reduce infection risk, based on studies showing the rate of air exchange to be better than air conditioning units (7, 8).
During the last major pandemic, the flu of 1918, emergency tents were used as wards due to the overflow of patients from hospitals. It soon became apparent that the open-air patients recovered quicker, and hospitals adopted the practice of keeping windows open to create a constant cross breeze for indoor patients (9). This strategy has also been employed for tuberculosis patients, with similar success. We are fortunate that the current pandemic has hit at this time of year - we can open our windows and enjoy moderate temperatures as well the signature sights and sounds of spring.
In the last article we discussed the role of vitamin D in keeping our immune systems strong, and the role of regular daylight in melatonin production; on top of this, sunlight has disinfectant properties. In developing countries it can be used to disinfect water: placing dirty water in a clear bottle for six hours in the sun (or for two cloudy days) neutralizes pathogens lurking in the water, making it safe to drink and reducing diarrheal disease (10).
Looking at potential pathogens in the home environment, a recent study found that sunlight reduces the bacteria in dust: rooms with sunlight had half the bacteria in dust samples compared with dark rooms, and this was true even if the windows were closed (filtering out most of the UV light) (11). What was really interesting about this study was that rooms with sunlight exposure had different microbial compositions too, with more ‘outside’ microbes than human microbes, compared with dark rooms. So, keep the shades open even if the windows aren’t open, to reduce the likelihood of germs proliferating in your house. Plus, plenty of light during the day will support your circadian rhythms, making it easier to get a good night’s sleep.
Sleep: quantity and quality
Good quality sleep is important for optimal immune function. While we’re sleeping the effectiveness of immune cells called T cells is enhanced (12), and the body produces and releases more cytokines (proteins that have a regulatory effect on the immune response) (13). These and other immunological factors impact the body’s ability to fight off any infections that might come our way.
Consistently getting less sleep than we need each night (at least 7-8 hours for adults) suppresses our immune function, and, according the CDC, more than 1/3 of us are falling short of that minimum on a regular basis (14). This chronic sleep deprivation puts us at higher risk of catching colds: in one study, those who slept for <7 hours per night for a two-week period were three times as likely to get a cold than those who slept for >8 hours, and those who had lower quality sleep (even if they got enough hours total) were also five times as likely to get sick compared with those who slept soundly (15).
Getting better quality shut-eye may require cleaning up your evening habits, something called ‘sleep hygiene’ (16). Things like eating too close to bedtime, drinking caffeine, drinking alcohol, and looking at electronic devices in the evening hours can all make it harder to fall asleep and stay asleep. Getting enough daylight during the day and minimizing bright lights (particularly blue light from screens) at night will support melatonin production and promote healthy sleep cycles.
Alcohol might help you fall asleep faster and it can feel like you’re sleeping more deeply, but it actually disrupts sleep patterns resulting in less REM time, which is the most restorative phase of sleep (17). Too many drinks can also suppress breathing, causing snoring and sleep apnea, which isn’t what you want if you’ve got a respiratory tract infection. Aside from its effect on sleep, drinking too much alcohol also has inhibitory effects on the immune system, increasing susceptibility to pneumonia and other acute respiratory syndromes (18). The occasional drink isn’t likely to cause any major problems, but moderation is key.
Regular alcohol consumption can sometimes be a coping mechanism for chronic stress, another lifestyle factor that can negatively impact our immune function (19). Simply put, stress is experienced when circumstances are beyond our abilities to cope with them; the body responds by mobilizing additional resources (e.g. cortisol) to help us meet the demands of the situation. Short term stress responses are necessary and appropriate, but chronic stress causes excessive inflammation in our bodies and decreases infection-fighting white blood cells (lymphocytes), leaving us vulnerable to infection (20) .
To reduce stress levels, try deep breathing or meditation - even 10 minutes a day can be beneficial for stress reduction, and a recent review found that mindfulness meditation may also improve immune function (21,22). Try sitting quietly and focusing on your breath; choosing a phrase to repeat to yourself can keep your mind off distracting thoughts. There are also various apps available now offering free guided meditations, for anxiety, general relaxation, and sleep, among others.
Even though we are socially isolating to reduce the spread of COVID-19, staying social (from a safe distance) can benefit our immune health. The National Institute on Aging cites social interaction as a contributor to stronger immune function in the elderly, with lower levels of IL-6 (an inflammatory cytokine) observed in those with stronger social ties (23). Spending quality time with friends and loved ones is good for our overall health too - we are a social species, and we do best when we are in community. Video chatting with friends and family can help to keep us connected.
The final thing to remember is the importance of self-care. Whatever situation you now find yourself in - whether juggling a job and homeschooling with a houseful of kids, or alone and possibly unemployed - do something every day that refuels you, so that you can continue putting your best foot forward, for as long as it takes for this to pass. Some of the things on this list can be considered self-care, but it’s going to be different for everyone: take a bath, lock yourself away for half an hour with a good book, give yourself a pedicure, write a letter or a poem, start an art project, take a break from social media, sing, dance, plan a post-COVID vacation, say no to something or say yes to something - anything that will make you feel recharged and relaxed amongst all the chaos. Self-care may seem like self indulgence, but it isn’t, it’s self preservation!
1) Nieman & Wentz (2019). Journal of Sport and Health Science. Volume 8, Issue 3, Pages 201-217. https://doi.org/10.1016/j.jshs.2018.09.009
2) Nieman (2000). Med Sci Sports Exerc, 32 (Suppl. 7) pp. S406-S411
3) Twohig-Bennett & Jones (2018). Environmental Research. Volume 166, Pages 628-637. https://doi.org/10.1016/j.envres.2018.06.030
4) Kuo (2015). Front. Psychol., 25 August 2015 | https://doi.org/10.3389/fpsyg.2015.01093
5) Li (2010). Environmental health and preventive medicine, 15(1), 9–17. https://doi.org/10.1007/s12199-008-0068-3
6) Li, Morimoto, Nakadai, Inagaki, Katsumata et al. (2007). Int J Immunopathol Pharmacol. 20(2 Suppl 2):3-8.
9) Hobday & Cason (2009). The open-air treatment of pandemic influenza. American journal of public health, 99 Suppl 2(Suppl 2), S236–S242. https://doi.org/10.2105/AJPH.2008.134627
10) CDC. https://www.cdc.gov/safewater/solardisinfection.html
11) Fahimipour, Hartmann, Siemens, et al. (2018). Daylight exposure modulates bacterial communities associated with household dust. Microbiome 6,175 https://doi.org/10.1186/s40168-018-0559-4
12) Dimitrov, Lange, Gouttefangeas, Jensen, Szczepanski, Lehnnolz, Soekadar, Rammensee, Born & Besedovsky (2019). J Exp Med 216 (3): 517–526. doi: https://doi.org/10.1084/jem.20181169
13) Besedovsky, Lange & Born (2012). Pflugers Archiv : European journal of physiology, 463(1), 121–137. https://doi.org/10.1007/s00424-011-1044-0
15) Cohen, Doyle, Alper, Janicki-Deverts & Turner (2009). Sleep habits and susceptibility to the common cold. Archives of internal medicine, 169(1), 62–67. https://doi.org/10.1001/archinternmed.2008.505
18) Sarkar, Jung & Wang (2015). Alcohol Research : Current Reviews, 37(2), 153–155.
22) Black & Slavich (2016). Mindfulness meditation and the immune system: a systematic review of randomized controlled trials. Annals of the New York Academy of Sciences, 1373(1), 13–24. https://doi.org/10.1111/nyas.12998
23) Friedman, Hayney, Love, Singer, Burton & Ryff (2007). Plasma interleukin-6 and soluble IL-6 receptors are associated with psychological well-being in aging women. Health Psychology, 26(3), 305–313. https://doi.org/10.1037/0278-622.214.171.1245
Hi, I'm Amy. I'm a nutritionist in the DC area, working with clients of all ages: from prenatal and pediatric, through to post-menopausal and geriatric. I'm all about straightforward, evidence-based health & wellness advice - because life in the modern world is complicated enough!