How to boost immunity

Covid-19 is everyone's biggest health fear right now but common colds, stomach bugs and respiratory infections can ruin your fitness goals. How can you power up your health and immunity so you can keep riding?

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For decades Professor Neil Walsh has been researching how to keep athletes on their bike and out of the doctor’s surgery. The Liverpool John Moores University academic is an expert in immunology, nutrition and exercise science and has studied training loads, sleep quality, nutritional plans, psychological stresses, temperature extremes and lifestyle behaviour to work out how best to optimise athletes’ immunity. He is as worried about Covid-19 as the rest of us but he knows that any illness – from sore throats and colds, to gastric bugs and respiratory infections – can ruin a training block, a race or a season.

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“Athletes do have a problem here: after injury, illness is the second most widely reported reason for underperformance and missed training,” explains Professor Walsh via Skype. “So if we can get an extra 10-20 days of training per year by helping athletes avoid silly gastrointestinal infections or respiratory infections, that is a boon. If an athlete gets sick ahead of the Tour de France, it can be career-defining.”

According to the English Institute of Sport, respiratory and gastrointestinal illnesses are two of the most common health issues experienced by athletes. One study suggested 70 per cent of illnesses suffered by Olympic athletes resulted in a complete absence from training and competition. But this is a crucial issue for amateur riders too: illness will limit your ability to train, dilute your fitness, reduce your ability to do your job effectively, and hamper the quality of your life at home. With mood-boosting bike rides an important physical and mental lifeline for many cyclists right now, staying healthy is more important than ever.

Experts have long debated whether cyclists and other athletes are more or less vulnerable to infection than the general population. Professor Walsh says that, in some ways, athletes have the same risk factors as everyone else: bad hand hygiene, inadequate nutrition or poor sleep will leave athletes more susceptible to illness, and athletes suffer a familiar spike in respiratory infections in the winter months. But he says athletes have some unique issues to deal with: a punishing training load; potential nutritional deficits; enhanced exposure to germs from group workouts and mass participation events; a lot of time spent travelling; and the draining psychological stresses of training and competition.

Most riders don’t think about their immune system in the same way they agonise over their body weight or power output. But the coronavirus has left us all reflecting on our immunity. In this strange new world, in which a trip to the supermarket can seem hazardous, even cycling can seem shadowed with new dangers. This could be an important
wake-up call.

“I always see athletes with their fingers in their mouth or rubbing their nose or their eyes, which is a great way to self-inoculate and give yourself the common cold or other respiratory viruses,” warns Professor Walsh. “At the Tour de France you often see riders sharing bottles, which is very risky.”

Hi to Hygiene

So our new and improved awareness of hygiene is no bad thing. But could exercise in itself be a problem? Some experts believe that extreme forms of training – such as fasted, low-carb, high-intensity or high-volume training – can leave your body depleted, triggering a surge in stress chemicals that hamper your immune system, providing an ‘open window’ for infections. But Professor Walsh is one of the many global experts who believe there is not enough evidence for this. Some scientists now claim that hard training actually heightens immune surveillance.

“The old research is a bit one-dimensional,” cautions Professor Walsh. “The studies previously showed that when riders go on a hard training camp to somewhere like Tenerife, some get sick, so people think, ‘Ah, it must be the training.’ But they had the anxiety of travel and flights; they had exposure on the planes and at the airport; they had food they’re not used to eating; they’re not sleeping in their normal bed; and they had the stress of training. So the causes of infections are really multifactorial.”

The debate continues but all experts agree that regular exercise helps to support immunity and should be encouraged. In an important article for Exercise Immunology Review earlier this year, experts from both sides of the argument reached the consensus that “regular bouts of moderate to vigorous intensity exercise are beneficial for the normal functioning of the immune system and likely help lower the risk of respiratory infection.”

According to Professor Mike Gleeson, emeritus professor of exercise biochemistry at Loughborough University and author of Eat, Move, Sleep, Repeat, exercise improves immunity by boosting your blood circulation. This increased blood flow sweeps an army of white blood cells (immune cells) into your blood stream to hunt down pathogens and destroy them.

“First, the white cells, which were stuck to the inner lining of your blood vessels are washed into the blood stream and that process alone pretty much doubles your white blood cell count,” explains Professor Gleeson. “But if you exercise for more than an hour, you also get cells coming in from the spleen and from the bone marrow. These get circulated around the body and into your lymph glands where they present any pathogen-related material which they’ve picked up on their travels around your body. The glands then act as a kind of filter: the immune cells located there react to any microorganisms deposited there and then produce the appropriate defensive response.”

In a review for the European Journal of Sports Science, Professor Walsh outlined some key recommendations to help manage your training load in a sensible way: never increase the volume and intensity by more than five to 10 per cent per week; increase the frequency of shorter, spiked training sessions rather than enduring fewer but longer sessions, and plan an easier recovery week after every second or third week. Stick to those rules and you can enjoy the immunity-strengthening benefits of exercise without triggering stresses, which might (or might not) reverse the process.

The best way to prevent illness is, of course, to avoid microbes, viruses, bacteria and pathogens in the first place. Good hygiene is your best weapon.

“If you’ve been sweating on your handlebars and let that dry, that can act as a source of nutrition for bugs to grow on,” warns Professor Gleeson. “So always clean your seat and handlebars with soap and water. You don’t need to use alcohol or gels, which might damage the fabric. Always clean your drinks bottle with boiling water and washing up liquid and rinse it out with cold water.” Dr Philip Tierno, clinical professor of pathology at NYU Langone Medical Center, has said that water bottles collect bacteria like “barnacles on a boat” and should be scrubbed with a brush to get rid of the dangerous biofilm that coats the inside of the bottle.

Professor Walsh suggests athletes should start paying more attention to their hands. “Make sure you don’t self-inoculate by touching your eyes, nose or mouth when you’re riding,” he advises. “And keep things clean. Team Ineos is very careful about not sharing cutlery at the breakfast table and cleaning surfaces regularly. But the first rule is always: avoid sick people. People say: ‘Well, that’s stupid.’ But now we all understand.” Carrying hand sanitiser for mid-ride bathroom breaks might be worth the extra weight. And riders at Team Ineos regularly disinfect the inside of helmets too.

Diplomatic immunity

Like any fighting force, your army of immune cells marches on its stomach. A balanced diet is important for immunity: macronutrients aid immune cell metabolism and protein synthesis, micronutrients support antioxidant defence, and glucose, amino acids and fatty acids help fuel your immune system. “The main thing is to eat a healthy diet and to match your energy intake to your energy expenditure so you aren’t depleted,” advises Professor Gleeson. “Eat lots of fresh vegetables and fruit. These contain polyphenols and flavonoids, which help your immune system. Make sure your plate looks colourful, with tomatoes, peppers, carrots or squash and leafy greens. You can eat a large volume without worrying about calories but they will keep you healthy.”

Cyclists have become increasingly aware of the importance of protein for muscle recovery and endurance but it also plays a surprising role in your immunity.

“If you had to pick one macronutrient, I would say that adequate protein intake is the most crucial,” explains Professor Walsh. That’s because key weapons in your immune system, such as antibodies and immune cells, are dependent on protein. Professor Gleeson suggests athletes take 1.2-1.6 grams of protein per kilogram of body weight per day for optimal immune function, as opposed to the 1.2 grams recommended for the general population.

In a compelling new article for the journal Sports Medicine, Professor Walsh promoted the importance of “tolerogenic” supplements – in other words, supplements like the antioxidant vitamin C, anti-inflammatory vitamin D, and gut-protecting probiotics, which might not stop you getting ill but could help you to better “tolerate” any illness and reduce your symptoms. “You almost want to dampen the immune system’s response to an infection: not too much because then you don’t have your weaponry, but often what makes your bug really quite nasty or long-lasting is if you’ve got an almost overly zealous immune response,” he explains. “The inflammation that is helping you kill the bug is also making your nose runny and your throat sore, so you feel like rubbish. Vitamin C and vitamin D can help. You might not see a lowered incidence of infection but you might have a less severe or long lasting infection. Although the evidence is quite poor, we also see that if you take probiotics you get similar benefits in terms of the severity and duration of infections.”

Professor Gleeson adds that this approach becomes especially important when you first develop symptoms of illness. “If you get a sore throat or a runny nose, take some zinc lozenges,” he suggests. “It has been shown that these can actually reduce your duration of illness by a third, or three days.” That’s because zinc is an antiviral agent that is believed to stop the common cold virus docking with cells.

Sleep is also incredibly important for immunity. “We have done some work which showed that army recruits who sleep six hours or less a night are four times more likely to get a respiratory infection than those army recruits who sleep more than six hours,” explains Professor Walsh. “And general population studies show that individuals who sleep less than seven hours seem to get more respiratory infections.”

The quality of your sleep is also important, according to Professor Gleeson: “In one study, people whose sleep efficiency was rated 98 per cent – very good – had five times less likelihood of developing symptoms as people whose sleep efficiency was less than 92 per cent.” In his new book, he lists a series of sleep-boosting tips: avoid caffeine and heavy meals late at night; don’t use phones or laptops before bed, as the blue light blocks the sleep-inducing hormone melatonin; keep different duvets for different times of the year, switching between 5, 10 and 13 tog as the seasons change; use blackout blinds or curtains; and stick to a regular sleep schedule.

Science is making it clear that athletes can only protect their immunity by taking a multi-faceted and holistic approach.

“The best way to think about your immunity is with a hub and spoke model,” concludes Professor Walsh. “Exercise stress is one component, but you also have life stress, nutrition, sleep, travel… all of these factors need to be right. Even when you look at exercise, it is very hard to separate physical and mental stress. Because if you are pushing hard in a time trial, there is the physical stress, but trying to hold that heart rate for 25 miles, the mental pain and stress is immense. And if you do a big race, you’ve prepared for riding in the hills, but you’ve not prepared for the travel, the poor sleep and everything else. We’re now realising that it’s probably what happens outside of riding the bike that’s important.”

Words: Mark Bailey

Photo: Getty

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This feature first appeared in issue 368 of Cycling Plus. To subscribe to the magazine and receive a free Lusso Merino Jersey worth £65, head over here