So, how can you best protect yourself against bugs? Most people would accept that boosting your immune system is a good idea, though many may be a bit vague about what that actually means.
However, scientists are now discovering precisely how the body’s defences function. And what they’ve learned is already providing practical ways to help you stay healthy, for longer.
The immune system has three basic forms of defence, explains John Curnow, senior lecturer in immunology and infection at Birmingham University.
The first line are cells called neutrophils and macrophages. They basically swallow and kill bacteria
Then there are T cells, which kill any cells that have been infected with a virus or become a cancer. The final group are B cells, which help us produce antibodies to stop viruses getting inside the cells in the first place.
The bad news is that after 65 this system basically packs up, explains Professor Janet Lord, director of the Centre for Healthy Ageing Research at Birmingham University.
“The immune system has developed through evolution to get us through reproduction, after which it is simply not designed to keep you going into old age,” she says.
“We make fewer T cells, the antibodies we produce are not as strong, and cells such as neutrophils are less able to ingest and kill bacteria.” This has profound consequences for health in old age. Vaccinations are a key example of this. When younger people are given a ‘flu jab, for instance, four out of five of them will produce enough antibodies to protect against infection.
However, fewer than half of those over 65 will produce enough antibodies, says Prof Lord. That’s because their B cells don’t work as well. Also, their bacteria-killing cells are not as efficient at detecting an infection.
Even when they find bacteria, they can only swallow up around half as many bugs as a young person’s can.
“The result is that older people are more susceptible to infections both at home and, importantly, in hospitals,” explains Prof Lord.
But while the decline of your immune system appears to be inevitable, how quickly this happens is still very much in your control, she insists. “It’s never too late to make changes that will have a significant impact on your immune system and quality of life in your 60s, 70s and older.”
Here we reveal the latest thinking on how to support your immune system - whatever your age.
* DON’T BOTHER WITH THE GYM - TAKE A WALK
Physical activity really does make a difference, and the good news is that it doesn’t involve breaking out into a major sweat.
The theory is that “stressing” the immune system through exercise makes it more robust.
People who exercise for at least five days a week and feel fit cut their chances of having a cold by between 43 and 46 per cent, according to a study published this month in the British Journal of Sports Medicine.
And half an hour of moderate aerobic exercise - brisk walking or swimming - a day doubled the body’s response to the ‘flu vaccine, a recent U.S. study found.
“But 30 minutes a day for most people, particularly the elderly, simply isn’t realistic,” says Prof Lord. And, she adds, you don’t have to go to the gym.
“A brisk walk where you’re slightly out of breath and have started to sweat signifies moderate - but significant in terms of immune response - stress is being placed on your cardiovascular system, with real benefits,” she says.
* LOSE WEIGHT, GENTLY
We all know that being overweight is a risk for heart disease and diabetes, but it also weakens your natural defences. Prof Lord explains: “Fat secretes hormones that suppress the immune system. Lowering your body fat content can have a positive effect on your immune response.”
But drastic weight-loss plans aren’t the answer. A recent U.S. study found that rodents on calorie-controlled diets were more likely to get ill than those getting enough food. “Cutting out food groups such as carbohydrates or fats completely could weaken the immune system,” warns dietician Dr Sarah Schenker of the British Nutrition Foundation. “It is no good eating badly, then spending a fortune on megadoses of vitamin C.”
* REST BEFORE A JAB
just one night’s bad sleep can halve the effectiveness of your immune system, U.S. researchers have found.
It seems our levels of protective T cells are reduced while inflammatory cells go up if we are sleep-deprived, leading to a greater risk of developing a cold or ‘flu.
Lack of sleep also influences how we fight illnesses once we come down with them. John Park, who specialises in sleep medicine at the Mayo Clinic in Minnesota, says: “We know that our immune response is suppressed when we are sleep-deprived and we develop fewer antibodies to certain vaccines. It takes longer for our body to respond to immunisations, so if we are exposed to a ‘flu virus, we may be more likely to get sick than if we are well-rested when vaccinated.”
* GET OUT AND ABOUT
The “sunshine vitamin”, vitamin D, is the latest focus for immune researchers, says Prof Lord. “It’s only in recent years that we’re starting to really understand how it impacts on the macrophages, the immune cells that ingest and kill bacteria such as those that cause TB,” she adds. Although it can be obtained from food such as oily fish and eggs, vitamin D is predominantly manufactured in human skin exposed to the sun.
“The sunny climate of southern Europe combined with a diet high in vitamin D foods such as oily fish may explain the health benefits of the Mediterranean lifestyle,” says Prof Lord.
She estimates that up to 80 per cent of older people in the UK lack vitamin D, which may also contribute to their increased susceptibility to infections.
“All you need is 20 minutes a day in sunlight to restore healthy levels of vitamin D or, failing that, a daily low-dose supplement,” she says.
* AVOID STRESS - IT REALLY CAN KILL
Stress has a “huge” impact on the immune system, says John Curnow. “We know the immune system’s effectiveness is related to levels of cortisol. Persistent levels of stress raise levels of this hormone to harmful levels.”
Stress has been shown to affect the ability of neutrophils to kill bacteria. When researchers compared the stress from three common causes - hip fracture, bereavement and looking after someone - they found losing a loved one in old age can have as damaging an effect on neutrophils as fracturing your hip.
“It’s why so many older people die not long after their spouse. We often say people die of a broken heart, but our research suggests they actually die of a broken immune system,” Prof Lord says.
* TAKE “GOOD” BACTERIA AFTER ANTIBIOTICS
A key area is diet, specifically probiotics, the “good” strains of gut bacteria which play an important role in the immune system.
“Many plants and vegetables we eat contain micro-organisms that stimulate our own defences - in effect, we piggy-back the defence systems they’ve developed to protect themselves,” says Professor Ron Cutler, virologist at Queen Mary, University of London. “Probiotics can replicate and enhance this mechanism, stimulating the immune system, preventing invading bacteria from establishing themselves. The real benefit from probiotics seems to be after taking oral antibiotics, which get rid of the ÒfriendlyÓ bacteria in your digestive system.”
A healthy, balanced diet is also paramount, but “some foods positively bolster your defences”, suggests Dr Schenker. She says there is good evidence that selenium (in Brazil nuts), iron (in red meat and pulses), zinc (in shellfish, cereals and dairy products) vitamins A (in carrots, butternut squash, orange or yellow peppers), C (citrus fruits) and E (in seeds and oils) all benefit defences. And what about “immune-boosting” supplements? The herbal supplement echinacea is worth considering, she says.
A Lancet study found it can reduce the time you’re infected with a cold by 1.4 days.
But take it only when you have a cold, warns Dr Schenker, as the benefits are effective for only up to two weeks. “Take it any longer and it could prevent your immune system from working properly.”
* SO WHAT DO THE EXPERTS DO?
Professor Ron Eccles, director of the Common Cold Centre at Cardiff University: “I always wrap a scarf around my nose as soon as it gets colder. Our noses are the first line of the immune system - and if your nose is cold it slows down the action of the cilia, the hairs in the nostrils that brush away bacteria and viruses, so giving them more chance to invade the body.”
Dr Mike Smith, GP and author with a specialist interest in colds and ‘flu: “Whenever I have a sore throat, I always keep away from other people. By the time you have a sore throat, your body is already fighting the infection.
“Keeping away from other people is about looking after yourself, as it limits the chance of secondary infections latching onto your weakened immune system.”
Professor Janet Lord, director of the Centre for Healthy Ageing Research at Birmingham University: “I run for 30 minutes every morning before work - it also gets me out in the sunshine, which means I’m certainly not short of vitamin D.”
John Curnow, senior lecturer in immunology at Birmingham University: “I make sure I eat healthily and manage stress. Knowing when you’re feeling stressed and finding ways to defuse it - even if that’s just going for a walk - can really help.” - Daily Mail