Part 4 in the 7 part series: For king and country – tend to your immune system

This article was originally published as a guest editor post at foodpharmacy.se

By: Graeme Jones, clinical physiologist and CEO at Nordic Clinic Stockholm.

One thing I have realised over the last 15 years working in Functional and lifestyle medicine, is that what I thought I was doing well at in regards to sleep and exercise, I clearly was not. Turns out even at a grand old age of 37, I am fitter and healthier than I was in my 20’s, and my numbers continue to get better over time as I optimise my routines.  As one example, over the last 16 months I have managed to improve my deep sleep by a WHOLE hour whilst sleeping the same amount of time! But what is the link here between, exercise, sleep and the immune system? Why is the immune system so important?       

The immune system plays an important role in protecting us from infectious agents. There are several layers to this process:

• Mucosal barriers hold pathogens (infections that cause disease such as bacteria and viruses) at bay – Think of the mucosa like a moat around a castle as the first line of defence 
• Epithelial cells prevent entry if the mucosal barrier is breached – The castle walls
• Local immune cells patrol points of entry – Guards on control around the walls
• Systemic immune cells that prevent circulation in the blood – Inner-castle guards

Furthermore, there are 2 separate responses called innate immunity (we are born with) and adaptive immunity (our immune system learns). Innate immunity is the first response, creating inflammation and signaling that there’s a problem. But innate immunity is general and does not have memory. The adaptive immune response, on the other hand, swings into action after the innate response. It targets the specific invader and provides memory so that reinfection does not occur.

Lifestyle plays an important role in optimal immune function. Two critically important lifestyle factors that create a strong, robust immune system are sleep and exercise. Both affect all aspects of immunity, and as such, should be part of any plan to optimise immune function. When patients attend Nordic Clinic and report immune system dysfunction, one of the first lifestyle factors I consider is sleep, so let’s review some connections between this strange state we spend a whopping third of our life in. 

Sweet Dreams, Sweet Defence 

Sleep and the immune system share a reciprocal relationship. On the one hand, immune activation drives changes in sleep believed to play a role in promoting a healthy immune response. On the other hand, poor sleep quality and duration has a negative impact on all aspects of immune function.

Sleep deprivation negatively impacts the innate immune response by driving chronic inflammation¹. One of the causes of this increase in inflammation is bacterial invasion into the blood and body from the intestinal microbiome, following a decrease in the barrier integrity.² This impairs immunity as both the creation and resolution of inflammation are active processes. Chronic inflammation not only damages pathogens, but also the tissues they infect. 

Messengers called cytokines can drive up inflammation and lower it. Lighting the fire of inflammation without putting it out through the release of anti-inflammatory cytokines towards the end of infection leads to collateral damage to tissues. This is the mechanism behind the cytokine storm, which increases mortality during infection. In that regard, the pathogen doesn’t kill you, the response of your immune system does, and it seems sleep could be an important player in helping to regulate the response of the immune system. 

Sleep also plays an important role in adaptive immunity. T cells are the soldiers of adaptive immunity, carrying out the marching orders by targeting infectious agents. They do this by sticking to pathogens and infected cells and killing them. During sleep, T cells become more “sticky” and are better able to stick to pathogens and kill them³. 

In line of this, two studies found that sleep was an important predictor of immunity toward the common cold. The study showed that participants who slept less and had poorer sleep quality had a dramatic increase in their likelihood of developing cold symptoms when researchers deliberately infected them with rhinoviruses. The risk was as much as 5.5 higher.^4,5  Also, according to another study, those who sleep less than 6 h per night were at significantly greater risk of developing pneumonia compared to those sleeping 8 h per night.⁶

Image source⁸

Move That Body – Put Your Guard up!

Exercise has many different mechanisms through which it promotes healthy immune function. First and foremost, regular exercise decreases systemic inflammation, both independently and through decreases in fat mass⁷. At high levels, body fat functions as an endocrine (hormonal) organ that secretes inflammatory cytokines into the bloodstream. That’s why the obese and type 2 diabetics see more frequent infections.

Both short and longer duration exercise also increase immunosurveillance. Exercise functions as an acute stressor, and damage to tissues puts the innate immune system on alert by increasing white blood cells. In addition, the lymphatic system which distributes these cells to tissues is almost entirely dependent on muscular contraction to distribute white blood cells. As a result, you have more immune cells that are patrolling the entire system more frequently⁸. Exercise literally puts more guards on patrol! 

Finally, regular exercise helps prevent the age-related decline in immune function called immunosenescence⁹. As we age, the immune system shifts, causing an increase in chronic inflammation AND a decrease in adaptive immunity. This change causes the elderly to be more susceptible to infection, and have a harder time fighting one off when infected. 

Regular exercise training, particularly aerobic exercise, helps put the brakes on immunosenescence (the gradual deterioration of the immune system with age). As a result, those who maintain exercise as a habit throughout life are better able to mount an immune response when infected as they age.

Also, the benefits of exercise for health at large are well known. In support of this, a recent study found that those who take 8 000 or 12 000 steps a day have a dramatic decrease in all-cause mortality compared to those who take 4 000 steps a day (51 and 65% lower risk of death over ten years, respectively.)¹⁰ 

Taken together, one cannot overstate the importance of behavioural factors such as sleep and exercise for health. Chronic sleep deprivation and a sedentary lifestyle are new phenomena considering the history of mankind. To honour our biology, we’d better get moving and go to sleep.

You find the other articles in the 7 part series “For king and country – Tend to your immune system” here:

Part 1: Your Immune System is Everything

Part 2: The Surprising Connection between the Gut Mocrobiome and Infections in other Organs

Part 3: Sunshine – the Forgotten Booster of Joy, Calm and Immune Resilience

References

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5143488/
2. https://journals.physiology.org/doi/full/10.1152/ajpregu.2000.278.4.r905
3. https://rupress.org/jem/article/216/3/517/120367/G-s-coupled-receptor-signaling-and-sleep-regulate
4. https://www.ncbi.nlm.nih.gov/pubmed/19139325
5. https://www.ncbi.nlm.nih.gov/pubmed/26118561
6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3242694/
7. https://www.frontiersin.org/articles/10.3389/fnagi.2019.00098/full
8. https://www.sciencedirect.com/science/article/pii/S2095254618301005#fig0003
9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6191490/
10. https://jamanetwork.com/journals/jama/article-abstract/2763292