*Note, this blog has been updated as of 10/2021 to include new research findings.
In light of the COVID-19 pandemic, there is a lot of interest in immune function and what, if anything, we can do to strengthen our immune system. Given how susceptible we all feel to this virus, it’s natural and productive to investigate how we can proactively strengthen our immune system.
There is no evidence that exercising, taking any supplements or herbs, or dietary changes will prevent you from getting the corona virus.
However, these all have been studied regarding their effectiveness in improving your immune system and how it can reduce the severity of symptoms from infection. Recently, a few studies have investigated the association between exercise and COVID-19.
Accordingly, I’d like to share what I’ve found that answers the following questions:
1. Does exercise improve your immune function?
2. What should you do when you are sick?
3. Does your diet improve your immune system?
4. Do supplements improve your immune system?
I’ll start with a quick summary. Excellent evidence suggests that exercise has a strong direct and indirect impact on improving your immunity. Proper nutrition is associated with improved immune function, but how is not clear. Some supplements may improve your immune system.
Let’s delve into that a little for more specifics that you can act on.
Does exercise improve your immune function?
There are so many benefits of exercise to not only address function and appearance, but also prevent or treat/manage non-communicable diseases. These are the diseases you can’t catch, but they cause millions of deaths and cost billions such as: heart disease, diabetes, cancer, depression, and musculoskeletal disease (arthritis).
But rarely do we talk about exercise in terms of treating communicable disease or infectious diseases. So it’s important that we investigate exercise’s role in facilitating a healthy immune system.
Years ago, I reported on the findings of an excellent review on the effects of exercise and immune function. (Rossi et al. Strength and Conditioning Journal, Dec 2010).The conclusion was that those who exercise regularly have significantly reduced incidence of sickness compared to those who do not. Mechanisms were proposed by which this occurs, yielding the conclusion that the effect of exercise was not solely due to a correlation of the fact that exercisers are generally healthier (less comorbidities, better nutrition, better sleep, etc).
However, it was suggested that the type of exercise mattered. In fact, if the exercise was moderate to high intensity, high frequency, and high volume, then your immune function was actually decreased in the short term, making you temporarily more susceptible to illness. This would impact an endurance athlete for example who trains 90 minutes 6 days a week, such as someone training for a triathlon. Some research indicated that this temporary immune system suppression could be counteracted by consuming a carbohydrate and protein drink before, during, and after exercise.
While most people don’t need to worry about this, as their workout duration and frequency are usually far lower than this, it would be concerning if you are an endurance athlete or someone who really likes that type of training.
More resent research calls into question whether high frequency, prolonged exercise actually does decrease the immune system function (Campbel, JP, and Turner, JE Front Immunol. 2018). They took a deep dive into the research regarding exercise and the immune system and addressed whether longer duration or higher intensity exercise suppressed the immune system.
Their review of the evidence yields some interesting conclusions:
1. High intensity/frequency/duration exercise does not suppress the immune system. It seems researchers citing otherwise misinterpreted salivary levels of IgA (an antibody that plays a critical role in immune function) as a signal of decreased immune function, which it does not. Also, prior research misinterpreted the decrease in lymphocyte numbers and function for 1-2 hours post exercise as an indication of immune suppression. Instead, what is really happening is that these immune cells are mobilized to the peripheral tissues “resulting in a heightened state of immune surveillance and immune regulation, as opposed to immune suppression.” So it seems that endurance folks don’t need to be so worried about immune suppression and exercise.
2. They reaffirm that frequent exercise heightens immune functioning, and that frequent exercisers have better responses to bacterial and viral antigens following bouts of exercise.
3. They provide evidence that regular exercise may limit or delay the aging of the immune system. This is critical for older adults, who as we all are now more aware, have a less effective immune system.
This means that endurance athletes don’t need to worry that their activity will make them more vulnerable to infections. Frequent exercisers can add a stronger immune system to the list of benefits of being active. And if you want to keep your immune system functioning well as you age, you should definitely exercise more.
A meta-analysis and systematic review gives us some more insights on the effects of exercise on immune function. After analyzing 55 studies through April 2020, the results showed that physical activity had some significant effects on improving immune function. (Chastin, S et al. Physical Activity, Immune Function and Risk of Community Acquired Infectious Disease in the General Population: Systematic Review and Meta-Analysis. Available at SSRN:https://ssrn.com/abstract=3673184 Pre-Print from the Lancet.)
They showed that increased physical activity:
• reduces risk of infectious disease by 31%,
• reduces risk of infectious disease mortality by 37%,
• increases immune function,
• increased antibody concentration after vaccination.
What about COVID Specifically?
Several research articles have been published recently showing how exercise improves immune function, echoing the findings shared above. While inferences were made about how this could affect COVID-19, only a couple of studies actually investigated the exercise and COVID connection directly.
In October 2020, researchers connected to the Mayo Clinic released evidence showing that max exercise capacity was inversely related to being hospitalized with COVID. (Brawner, et al Mayo Clinic Proceedings. Oct 2020) Another study published in April revealed similar findings. 48,440 COVID-19 patients in England found that inactivity was positively associated with a higher risk of severe COVID-19 outcomes.
Thus, both direct and indirect shows that exercise significantly improves immune function, and reduces COVID-19 severity.
Interestingly and not surprisingly, the lockdowns have negatively impacted activity levels. A systematic review in 2021 of over 60 studies showed a decrease in physical activity and increase in sedentary behaviors during the lockdowns compared to before. (Stockwell S, et al. Changes in physical activity and sedentary behaviors from before to during the COVID-19 pandemic lockdown: a systematic review. BMJ Open Sport & Exercise Medicine 2021.)
Other studies provide more specifics on the connection between lockdowns and activity levels. One found activity levels decreased by 30% (Ammar A , et al. Effects of COVID-19 home confinement on eating behaviour and physical activity: results of the ECLB-COVID19 international online survey. Nutrients 2020) and sitting time increased by 30%. Another found that in Europe, within 30 days of the implementation of lockdown restrictions, activity decreased by an average of 27.3%, ranging from 48.7% in Italy to 6.9% in Sweden (which during the dates of study never implemented lockdowns, only social distancing and limitations on gatherings). (Tison, et al. Annals Internal Medicine. Nov 2020)
What about when you are already sick, should you still exercise?
Moving away from COVID and focusing more broadly on any type of infection, let’s consider what the best course of action when you are sick, such as having a cold. Should you still exercise, or is that doing more harm than good?
There is a rule of thumb in the medical community that goes like this:
• If you have symptoms above the neck, exercise is fine.
• If you have symptoms below the neck, stop and rest
• If you have a fever, don’t exercise.
This is ok, but I think we can be a little more specific. So I’m going to create my own additions to the above rules that I think more accurately reflects the research and experience from someone that exercises and prescribes routines for a living:
1. If you have a fever, don’t exercise. Rest – a lot. Don’t stretch. Don’t stay home and work from your laptop in bed or answer emails. Simply rest or you will be sick longer.
2. If you have GI symptoms – Well, I don’t think I need to tell you what to do about that, so I’ll move on.
3. For other symptoms, I’ll break it down based on type of exercise and personality type:
Resistance training: low to high intensity, low volume (1-2 sets per exercise, 3-6 exercises) low frequency (1-3 sessions) low duration (20-40 minutes) low rest periods (2-4 minutes between sets)
Corrective exercises: Definitely fine
Dynamic warm-up: Definitely fine
Energy system training: Moderate intensity (under 80% max simply rated at less than an 8 out of 10 – ten being an all-out maximum), low duration, moderate frequency (3-4 times a week).
Beginners/fat loss: Focus on adequate sleep, diet, corrective exercise, dynamic warm-ups, and resistance training as above. I tend to give more encouragement for these clients to exercise when they are symptomatic (again, not if they have fevers). mostly because their exercise habit is fragile. Also they aren’t capable of exercising at the intensities that cause over training and immune compromise. They won’t burn a bunch of calories right now, so this is not the time to push to new limits. But this might be the time to keep the routine of their new and perhaps fragile fitness commitment intact.
At this stage, the focus is on learning the routine via proper technique anyways, and you can always push the sets and reps later. If symptoms allow, don’t back off how much weight they use. But cut out some sets and allow plenty of rest between sets. Circuit training and complexes may need to be backed down a bit. Intervals can be tolerated, but the work phase will not be nearly as intense.
Endurance athletes: I like them to take time off completely. They tend to overtrain and the endorphin high of training is too tempting to trust them to not chase it. However, if they must train (which I totally get – stress release, etc), again I suggest they focus on corrective exercise and some resistance training. Most will lose it mentally if they don’t do some aerobics, so they are advised to do so with very low intensity 20-30 minute walks or rides. Best to do this inside if they have chest congestion and it is very cold out, as this can irritate the respiratory tract.
Strength athletes: Pretty much the same as the beginner/fat loss people. There is somewhat of a mental issue here as well – but not like with the endurance athletes. The big difference is that training with weights at 70% of their max can still be tough to handle if they have sinus issues because the strength capacities are so high proportionate to others. It also depends on positions. For example, bench press and bent over rows may make their head feel like exploding due to sinus pressure. But lunges and chins might be fine because you are upright. On the other hand, if you have chest symptoms you’ll be fine as long as you stay away from complexes, circuits, high reps, and low rest periods which significantly tax the respiratory system.
Does your diet improve your immune system?
Every resource suggests that a healthy diet, including adequate macronutrients (protein, fats, and carbohydrates) and micronutrients (vitamins and minerals), is required for a healthy immune system. There are clear associations with poor immune function in those suffering with malnutrition.
However, very little quality research exists that tells us what precise healthy diet is best for boosting immune function. A very recent review highlighted this problem. While some studies indicate certain nutrients like fiber, healthy fats, and proteins are important in enhancing immune function, not enough interventional research on humans is available to give specific recommendations and give strong conclusions. (Venter, C. eta l, Nutrients Mar 19 2020.)
While that won’t stop many from veraciously touting specialized diets to boost your immune system, the facts are that we just don’t have enough research to back that up.
Meanwhile, continue to focus on eating healthy in a way that is sustainable for you and ignore strong claims to make changes based on enhancing your immunity until better research is available.
However, there is evidence that obesity effects the immune system. Evidence supports a strong association between obesity and COVID-19 symptom severity and death. (Popkin, BM, et al. Obesity Reviews. Aug 2020.) It’s well established that exercise and nutrition is related to obesity. Thus, this evidence supports an indirect link between COVID-19 severity, nutrition, and exercise.
Do supplements improve your immune system?
Many studies have been done on the effects of supplements on improving immunity or your ability to recover from illnesses such as colds. The research suggests that Vitamin C, Zinc, Vitamin D and seem to offer positive effects on either warding off infections or lessening symptoms. The research is backed by moderate quality evidence.
For example, a meta-analysis in 2018 showed that supplementing with vitamin C can shorten the duration of a cold and lessen symptoms. It’s important to note that this effect seems to occur only when you’ve been supplementing regularly, and likely won’t make a difference if you start when you’ re already sick. (Ran L, et al Biomed Res Int. 2018)
Zinc lozenges taken upon the onset of symptoms has reduced the duration of illness, but should be less that 100mg for less than 2 weeks to avoid GI and other side effects.
Vitamin D supplementation seems to prevent upper respiratory infections. ( Martineau AR, et al.. BMJ. 2017). And Vitamin D deficiency was shown to increase risk of COVID-19 by 50%. (Meltzer DO. JAMA Open Network Sept 2020)
I’d strongly recommend that you take a look at my go-to resource, examine.com. It is run by a trusted industry leader who hires top tier scientists to intensely research the quality of studies and dissect their conclusions. They then report their findings in readable form so we can all make educated decisions on supplements. They do not sell nor promote any supplements. They just report on the evidence, which is a great service. Take a look here for more research on the topic of supplements and immune function. They will have everything you need to know based on solid evidence.
We are all concerned about our immune system, especially now. It’s important that we all do what we can to enhance our immune function while not falling prey to poor evidence and unsubstantiated claims.
You can be confident that exercise will play a critical role in enhancing your immune system. Your diet will likely help, but no need to switch to anything beyond one that allows you to eat a healthy amount of protein, fats, and carbs, emphasizing fiber and nutrient rich foods like vegetables and fruit. And while some supplements might work, the evidence shows the effect is moderate at best, except when you have established nutrient deficiencies like low vitamin D levels.
As always, reach out to us to help you improve your health and fitness. While the average person has gained body fat and decreased activity during the first 18 months of the pandemic, our clients lost body fat and improved strength. Having the right support, coaching, and program tailored to your situation is the key. If we can help people during the height of the pandemic, we can certainly help you now, no matter your circumstances. Click here if you need help to get healthier and stronger.