For those of you on my mailing list, you’ll already know my colleagues at Loughborough University have organised a series of free COVID-19 Lifestyle Education sessions for GPs and allied healthcare professionals, which are also fully accessible to the general public. If you’ve not checked out the programme of events, then you can do so here and get yourself signed up to attend.
Last week, we kicked off with an excellent introduction to the immune system by Dr Martin Lindley, Senior Lecturer and Programme Director of the Biosciences programmes. Don’t worry if you missed it, you can catch the replay here.
This week we had a trio of talks on immune function. First up, was my friend and mentor Professor Lettie Bishop who gave us an introduction to exercise and immune function. Next up was Dr Tom Clifford who spoke about the importance of diet in immune function. Finally, I closed the session with a rundown of the role that exercise plays in preventing cancer, improving immune function in cancer patients, and the implications that COVID-19 has for cancer patients and survivors.
First up, coronavirus and cancer - what’s the deal? Well, unfortunately there’s not THAT much research to go on, but early studies from China, Italy and other sites of local infection suggest that cancer patients are amongst the “high risk” group - that is to say, there is a greater risk for major complications, i.e. hospital admission, ventilation and possibly even death.
Those most at risk are blood cancer patients and those in active treatment, which includes chemotherapy, surgery, immunotherapy and bone marrow transplants, due to immunosuppression. In particular, Hodgkin lymphoma, chronic lymphocytic leukaemia (CLL), acute myeloid leukaemia (AML), acute lymphoblastic leukaemia (ALL) and multiple myeloma (MM) are all in the high risk category.
But even those out of treatment may want to be extra cautious since the after-effects of cancer and the immunosuppressive effects of treatment can be long term.
How does our immune system protect us against cancer?
We have two different “arms” to our immune system: the innate (also called non-specific) immune response, and the acquired (also called adaptive or specific) immune response.
The first line of defense we have against all sorts of pathogens and disease comes from our innate immune response, and with cancer, it’s a particular type of cell called Natural Killer (NK) cells that serve to protect us. NK cells recognise and destroy rogue cancer cells. They also seek out and destroy virus-infected cells, which is important because when the immune system is struggling, this is when: A) the body is more susceptible to infection; and B) cancer cells in the body have an opportunity to grow.
Once NK cells have destroyed a rogue cancer cell (or cells), it secretes tiny proteins called cytokines, which act a bit like a homing beacon to signal to other immune cell types from the specific immune response to come and help in the “fight”. Amongst these specific immune cell types that come to help kill off the cancer cells are T cells, which are highly specific and only seek out and destroy cancer cells that express a particular protein on their surface that T cells have been primed to recognise. This is a little bit like a sniffer dog being given a piece of clothing and then being sent out to find a missing child. T cells get a “sniff” of the tumour and then roam around the body looking for other tumour cells just like it, and when they find them, they destroy them.
How does our immune system protect us against coronavirus?
In a very similar way, our immune system responds to viral infections, first by NK cells eliminating any virus-infected cells, and then by T cells that are primed to recognise and kill any other virus-infected cells that have escaped this first line of defense.
However, this clearly isn’t the full picture, otherwise we wouldn’t be in this current pandemic situation we find ourselves in.
So what went wrong?
There’s a lot we don’t know, but it appears that COVID-19 patients have fewer NK cells, and those NK cells they DO have are “functionally exhausted” (burnt out). In addition to this, low levels of T cells appears to be associated with mortality in COVID-19 patients. To make matters worse, it might even be that the virus can infect T cells themselves, causing them to “commit suicide”, rendering the patient with an even more suppressed immune system, which could mean the infection rages on.
How can exercise help prevent cancer?
Well, we know that exercise can reduce the risk of some (not all) cancers, including lung, colon and breast cancer.
How does it do this? Well, there are lots of different theories, and it’s likely to be multiple different ways, but immune function is one of the major players here. Patients who undertake moderate intensity exercise before and during chemotherapy have increased numbers of T cells and NK cells in their system. These immune cells also show higher levels of tumour cell-killing activity. And patients with higher numbers of T cells and NK cells generally have a better prognosis.
So, does exercise prevent viral infections?
Yes and no. Let me explain…
Moderate intensity exercise improves immune function and potentially lessens the risk and severity of upper respiratory tract viral infections. However, prolonged high intensity exercise actually causes immunosuppression. So if you want to optimise your immune system, regular, consistent, moderate intensity exercise is one piece of the puzzle.
Can exercise help us fight off coronavirus? Well, in all honesty nobody really knows yet. The most relevant study states:
“There is low quality evidence to suggest exercise has no impact on the rate and duration of acute respiratory infection, but may provide a small reduction in severity of symptoms.”
So I take that as: “it won’t do any harm”. I’ll take the reduction in symptom severity any day, thank you very much!
The current recommendations for cancer patients (and indeed ALL of us) is to participate in 150-300 minutes each week of moderate intensity exercise (this could be broken down into 5 x 30-60 minute bouts) OR 75-150 minutes of vigorous intensity exercise each week (5 x 15-30 minute bouts).
There is strong evidence to support the use of aerobic and resistance exercise in reducing cancer-related fatigue, improving quality of life and physical functioning in the cancer community. Aerobic exercise has also been shown to reduce anxiety and depression, and resistance exercise has been shown to reduce lymphedema. You can read more about this on the American College of Sports Medicine website here.
Be aware, however, that there are certain things that will affect an individual’s ability to exercise, including the type and stage of cancer, the specific treatment they’re receiving, and baseline stamina (endurance), strength and fitness level.
The take home message?
It’s important to listen to your own body!
What about those cancer patients or survivors who have had coronavirus? Well, in the general population, there is evidence that even after recovery from COVID-19, patients continue to experience fatigue, shortness of breath and reduced exercise tolerance. This is likely to be the same (if not worse) for cancer patients recovering from COVID-19, so the advice is to be gentle and kind to yourself, phase in gradual increases of physical activity, listen to your body and rest well. There’s an excellent resource on the Moving Medicine website about this here.
Next week, the sessions will be focussed on COVID-19 and obesity, with presentations from Dr James King and Dr David Clayton on exercise and diet in weight management. Don’t forget to sign up here.
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