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Our immune system is key to whether or not we fall prey to every passing cold, but what is it and how does it work? 'A good way to think of it is as an army with two 'divisions', which work in tandem to protect us against disease,' suggests Dr Peter Barlow, British Society for Immunology spokesperson and Associate Professor of Immunology at Edinburgh Napier University.
'The first division, the innate immune system, is the body's frontline of defence. It includes physical defenders, like the mucus lining of our nasal passages and tiny hairs called cilia, which help sweep away inhaled germs together with small molecules, called antimicrobial peptides, and other chemicals, called cytokines, which transmit information between cells.
Supreme multitaskers, these are in constant dialogue with other parts of the immune army, helping recruit immune cells to the site of infection and causing, in the case of a cold, the familiar sore throat and runny nose.' Cells from the innate immune system patrol areas of the body often exposed to infection, like the lungs and the gut, and release chemicals to kill viruses and bacteria. It's fairly non-specific, which enables it to react swiftly - sometimes within minutes,' explains Barlow.
The second division, the crack force known as the adaptive immune system, is slower but more specific. 'Adaptive immune cells analyse how best to respond to particular invaders,' says Barlow. Cleverly, once they've worked this out, they 'remember' every invader they have ever encountered enabling the troops to swing into action producing antibodies against anyone that pays a return visit.
Fiction. Catching a cold can harm your immune system against that particular cold virus so you avoid it or get it less severely if you encounter it again. And, provided your immune system is firing on all cylinders, it's unlikely to do much harm but our experts all agreed it's not a smart idea. Says Barlow, 'Not all respiratory infections are benign: some can be severe and damaging'. What's more, as he points out, 'Even if you manage to shake off a cold fairly easily you could spread it to others who are more vulnerable.' Having said that, as Stephen Morse, Professor of Epidemiology at the Columbia University Medical Center observes, 'Colds are so ubiquitous you'd probably have to become a hermit to avoid them completely'.
Fact. There's no doubting bad bacteria is found in all manner of places. A report from NSF International found a clean kitchen is the key to cold-prevention with the top six 'germiest' appliances including refrigerators, can openers, rubber spatulas and rubber sealed food containers. Most viruses and bacteria that cause colds are spread hand-to-hand or hand-to-food. So next time someone says, 'You haven't got a cold, have you?' when sipping from the same glass - they're thinking along the right lines. It goes without saying hands should be thoroughly washed with soap, not just water, before preparing food.
Fact. 'Most immune cells are found in our gut lining where they interact with the trillions of gut microbes (gut microbiota) that live there. 'When people are sick their gut microbiota changes while people with a healthy gut microbiota get fewer infections. We still don't know, however, whether this is cause or effect,' says Barlow. A diverse high-fibre diet is key to a healthy gut and immune system. In fact, one reason traditional remedies, such as garlic, are thought to work is via their effects on our microbes,' suggests Professor Tim Spector, of King's College, London.
Fiction. Sadly we become more prone to respiratory infections with the passing years - and they can be more serious. Why? The innate and adaptive immune systems become less effective at fighting off respiratory bugs. As Barlow, explains, 'We have fewer of certain types of immune cells and our immune cells stop responding as they should - something called immunosenescence.' It's one reason flu - and some other respiratory infections - are more likely to be severe and even fatal in later life. A good reason to make sure you get that flu jab if you're eligible.
Fact. 'Your genes, general health and whether you have encountered that particular or a similar strain of cold virus before all play a role as do diet and lifestyle,' observes Barlow. Vitamin D, for example, plays a major role in activating our innate immune system and low levels are linked to a higher risk of respiratory tract infections while vitamin D supplements may prevent them.
Being super clean, especially in childhood, can affect later resistance to germs too and, says Barlow: 'Those exposed to viruses and bacteria at a young age have a better immune response in later life'. Chronic stress also exacerbates respiratory infections although not, as previously thought, because it suppresses immunity but because it disarms one of the body's key ways of switching off those cytokines.
Fact. It seems 'good bacteria' in the gut act as a link between our gut lining cells and our immune system cells, helping to balance our immune response and switching it off at the right time. So should we take probiotics as a preventive measure? Says Professor Merenstein, of Georgetown University in the US, who has researched this, 'It makes some sense if you're someone who gets frequent colds.'
Says Professor Stephen Morse, 'Our grandmothers may not have had our sophisticated scientific knowledge, but much of their advice passes the test of time: rest, stay in bed, get plenty of liquids, stay warm and do whatever works best for you to relieve symptoms,' he advises.
Supplements that may help support the immune system during illness include zinc, probiotics, vitamin D and, if you're under physical stress (e.g. you're training hard at the gym every day) vitamin C. Think about adding in an all-round multivitamin and mineral supplement for extra insurance.
Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.