Could microbiome and diet be key to reducing hospital overcrowding this winter?
The gut microbiome and our diets are closely linked, and both interact with our immunity in complex ways we are only beginning to understand. Immune ‘boosting’ foods are usually gut-friendly foods.
A total of 7,832 patients spent time waiting on trolleys in Irish hospitals during July, according to the Irish Nurses and Midwives Organisation.
The top five most overcrowded hospitals were University Hospital Limerick with 1,824 patients, Sligo University Hospital with 615, St Vincent’s University Hospital with 592, Cork University Hospital with 591, and University Hospital Galway with 541.
The INMO has warned that the HSE must view this as an indication of what is now "inevitable this winter and must act accordingly". General Secretary Phil Ní Sheaghdha said the July figure is a “red flag warning” for the autumn and winter months ahead.
Missing from the discussion is the mounting evidence — post covid-19 — of the key role of diet in maximising the body’s ability to mount an effective immune response to infection.
The pandemic placed sub-groups of the population globally at high risk of severe disease and or death and highlighted the importance of the immune system — the natural defence mechanisms throughout the body which defend against attacks from invaders. It is becoming increasingly apparent that the immune system is much more sophisticated than previously thought and is a key factor in fighting off ageing, cancer and many other common diseases.
Recent evidence shows the response of the immune system is largely driven by environmental factors like diet and gut microbes. The good news is that this makes the immune response potentially modifiable.
There are two main forms of immune defence. The first is the innate system — a crude instrument where a perceived threat is met by circulating white cells that trigger a rapid inflammatory response to limit the damage. This is what happens to an allergic rash when pain, swelling and redness are the result of white cells rushing in and producing chemicals that alter blood vessels and produce fluid.
The second immune defence mechanism, adaptive immunity, is slower and more sophisticated. Specialised cells called ‘T’ cells, ‘B’ cells and ‘natural killer’ cells, either target the danger directly or form antibodies to neutralise the virus, then form memory cells to guard against future attacks. These cells lie dormant, waiting for the next wave of infection — as with Covid 19 — where we mount resistance to an attack, reducing the risk of serious infection or death.
Overreaction of the immune system can cause food allergies or autoimmune diseases where the immune system attacks cells in our bodies by mistake.
Professor of genetic epidemiology at King’s College London and author of , Tim Spector, says all of these factors influence our gut microbes and consequently our immune system.
"The immune system is in close and regular contact with the gut microbes, which as well as nourishing the cells of the gut lining, also send chemical signals to dial immune responses up or down."
In the 1980s, it became clear that acquired immune deficiency syndrome (AIDS) caused by HIV infection, often led to cancers that spread much more rapidly in AIDS patients than in people with healthy immune systems. Spector describes how every time our cells replicate, they produce DNA mutations that accumulate to produce microscopic tumour cells throughout the body.
Luckily the immune defences identify these mutations as ‘alien’ and destroy them.
"But when cancer-seeking immune cells are weakened by disease, poor diet or some immune-suppressant drugs, these micro-tumours go unchecked and can become life-threatening."
Recent evidence is also demonstrating the role of the immune system in slowing the effects of ageing. 90% of deaths from Covid-19 or seasonal flu occur in over-85 year olds because the immune system performance reduces with age.
Spector describes how when we are young with a healthy immune system DNA repair works well but as we age this system starts to fail. The failure in the immune system to detect defects in our cells as we age, and initiate repairs helps to explain why our bodies age and why we develop cancers with increasing years. The speed at which this degradation happens varies from person to person but is more rapid in people overweight or obese.
During the pandemic, people with obesity did not get the same immune protection from vaccines as people with a healthy weight.
Spector says that why this is the case is not entirely clear, diet quality and gut microbes are likely to play a major role.
Research by Tim Spector’s team into the benefits of vitamins for the immune system, surveying 2 million people in the US and UK, found no benefit whatsoever in taking zinc, vitamin C or garlic supplements to prevent covid infections.
Other supplements — vitamin D, omega- 3 fish oils, multivitamins and probiotics — showed no preventive effects in men and a small reduced risk of infection in women (7-27%).
Long-term or chronic inflammation — which can be thought of as an overstressed, overreactive immune system — increases the risk of heart disease and metabolic problems such as obesity, thanks to the complex interactions between the gut lining, short chain fatty acids and pro-inflammatory chemicals called "cytokines".
"It is now clear that that the gut microbiome can crucially modify chronic inflammation and that certain foods may have a protective role and others a stimulating role," says Spector.
Research published in (2021), involving over 1,000 healthy people filling in a detailed diet questionnaire, showed that people who ate a lot of vegetables had lower levels of white blood cells which meant that they had lower levels of inflammation and less risk of disease and infections.
The research team also identified a gut microbe called ‘collinsella’ that increased white cell levels and risk of inflammation, and was also associated with overeating ultra-processed food.
In spite of their high dietary fibre and polyphenol content, eating fruits has not shown a significant beneficial effect in preventing inflammation or heart disease in Spector’s studies.
This may be related to high sugar content of some fruits or because they are consumed in large amounts as drinks. A high sugar diet is also shown to be pro-inflammatory.
The gut microbiome and our diets are closely linked, and both interact with our immunity in complex ways we are only beginning to understand. Immune ‘boosting’ foods are usually gut-friendly foods. The benefits to the immune system can be wide-ranging in their effects including reducing allergy, fighting infections, boosting defences against ageing, and cancer.
"Looking after your diet helps your gut microbes to help your immune system do its job. It’s actually quite simple," concludes Spector.
An immune ‘boosting’ diet includes eating lots of fermented foods (yogurts, kefir, kombucha), fibre (onions, leeks, cabbages), and foods rich in polyphenols (berries, beetroot, nuts and seeds) and green leafy vegetables.
Enhancing the body’s natural immune response with a healthy diet is far more effective than any supplement and could be the missing ingredient to keeping hospital overcrowding to a minimum this winter.
Dr Catherine Conlon is a public health doctor in Cork and former director of human health and nutrition, safefood.
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