It is a perennial health question that has never seemed more relevant: just how can we boost our immune system and give ourselves the best fighting chance against infection?
Thousands of books, articles and blogs have been written on the subject (unsurprisingly, more than ever in the past 12 months), making audacious claims about specific regimes, diets and superfoods, which, they claim, will stave off illness and help us recover faster if we do succumb.
Meanwhile, chemist and supermarket shelves heave with products aimed at 'supporting the immune system' and other sufficiently vague yet intriguing promises. The problem is, there's barely a jot of evidence for any of it.
Now, a timely BBC documentary has put some of the best-known immune-boosting theories to the test and found that, in just six weeks, a few simple lifestyle changes can make a significant difference, giving our body the tools it needs to defeat the common cold and flu. And, yes, perhaps even Covid.
The Truth About... Boosting Your Immune System, which airs on Wednesday, features six volunteers who undergo a six-week crash course designed to turn around their underperforming immune systems.Insurance Loans Mortgage Attorney Credit Lawyer
David Richards is one of the participants in the BBC's experimental documentary, The Truth About Boosting Your Immune System
Each was picked as they'd admitted to having unhealthy lifestyles, such as boozing, eating too much junk food and doing little or no exercise – and suffering regular coughs and colds.
Blood tests at the start of the experiment confirmed that their immune systems were not functioning as well as they could be. Their new regime was nothing too unusual: a varied, balanced diet, high in fibre (yes, lots of fruit and veg), regular exercise and a good sleep pattern.
At the end of the programme, the participants not only felt better, but further blood tests proved their disease-fighting immune responses had become stronger.
Immunologist Professor Sheena Cruickshank, at the University of Manchester, helped oversee the experiment. She says: 'The rapid response seen was pretty surprising. Their blood tests revealed the plan led to an increase in cells that produce disease-fighting antibodies.'
The programme also reveals other, perhaps less obvious ways to help boost immunity, from massages to cold showers, which have immediate benefits.
Our immune system is just that – a network of organs, glands, cells and compounds throughout the body, which protect us from attack by viruses, bacteria, parasites and other pathogens. As we age, levels of some immune-system cells naturally wane, which is why we tend to become more vulnerable to infections of all kinds.
But age isn't the only factor – lifestyle plays a big part too. Alcohol, for instance, seems to have a wholly negative impact, even in relatively small amounts. Clinicians have long known that heavy drinking in the long term is associated with a raised risk of immune-related illness, such a pneumonia, slow recovery from illness and poor healing of wounds.
But, in fact, the effects can be near-instantaneous. When it enters the gut, alcohol alters the make-up of our gut microbiome – the trillions of microorganisms that live in our gut which play an important role in immunity.Insurance Loans Mortgage Attorney Credit Lawyer
This, in turn, damages immune cells in the blood, including our lymphocytes, which are responsible for sending out antibodies.
Antibodies play a vital role in immunity, attacking and destroying invaders such as viruses.
In an experiment, with blood samples taken before and after drinking, presenter Dr Ronx Ikharia, an emergency medicine specialist, downs three glasses of prosecco and finds it is enough to bring down levels of lymphocyte cells by as much as 50 per cent.
This could reduce the effectiveness of the body's immune response – and for this reason Prof Cruickshank says people should avoid alcohol around the time of having the Covid jab.
David Lloyd, 38, pictured doing a dance routine with his daughter for exercise, also took part in the experiment
'You need to have your immune system working tip-top to have a good response to the vaccine, so if you're drinking the night before, or shortly afterwards, that's not going to help.'
Alcohol isn't the only vice that can impact the body's immune response either. As the volunteers, all recruited from Crewe, find out, their choices in food and exercise are a major factors too.
Salesman David Lloyd, 38, admits he could be taking better care of his body. 'I like a bit of McDonald's, KFC, you know, fast food,' he says. When asked whether he would class his approach to exercise as relaxed, moderate or vigorous, David quips: 'What's exercise?'
Meanwhile, Ruth Minshull, 47, a personal assistant, says her lifestyle has become increasingly sedentary. She says: 'My diet has got worse, and I wouldn't even say I do a little exercise these days. I do no exercise, truthfully.'
And couch potato Nadiya Remtulla, 45, a car-leasing manager, suffers from constant colds.
At the start of the six-week experiment, blood samples are taken from the volunteers and measured for the number of two key sets of immune cells – neutrophils and lymphocytes.
Neutrophils are fast-responding immune cells that attack pathogens that can cause diseases as soon as they enter the body, while lymphocytes help the immune system 'learn' about different types of foreign invaders, and send out antibodies to fight them off.
If the levels of neutrophils in the blood are too high, it suggests that the body's immune system is over-active – sending out cells to fight infection when it is not there. Low levels of lymphocytes suggest that the body's ability to defend itself is impaired. In five out of six of the volunteers, test showed neutrophil levels were high, while lymphocyte levels were low.
According to Prof Cruickshank, the consequences could become serious. 'Over time, if the immune system is out of balance, you'll start to feel more run down. You'll become more susceptible to infection, such as colds, and infections will stay longer.' Prof Cruickshank warns: 'These people could suffer more severe Covid illness.'
The good news is that it's reversible. Prof Cruickshank's first step for the participants is to change what they eat. Their new diet is one that aims to build 'gut diversity' – the variety within the make-up of the organisms that live in the gut and form part of the immune system. Studies show a diet high in meat, saturated fats and sugar can, as alcohol does, create imbalances in the kinds of bacteria