If your winter training is frequently blighted by illness and infection, now is the time to prepare with an immune-boosting diet, says Wendy Martinson

A recently published IOC consensus document looked at the impact of training stresses and strains on illness and injury rates among athletes. Experts considered a whole range of issues that might raise the risk of health problems, including changes in training load, an over-packed competition calendar, psychological issues and excessive travel to produce practical guidelines for both elite and recreational competitors.

Taking part in competitions was found to be associated with an increased risk of illness, particularly when it comes to large events. Data collected from several Olympic games and international competitions shows up to 17% of registered athletes are likely to experience an episode of illness and that half of all acute illness among athletes affects the respiratory tract. Travel over the summer months can also leave you more vulnerable to infections.

In one study of elite sports people competing in a 16-week tournament, travelling across more than four time zones was associated with three-fold increased risk of illness.

But it is not just top-flight athletes who are more at risk of getting ill. Anyone in training needs to be on their guard against viruses.

Athletes more prone to infection

While moderate activity helps to boost the immune system, hard training can hamper it and studies have shown that intense training leaves athletes more vulnerable to catch a cold – or worse – than the general population. Why? Although exercise stimulates a powerful anti-inflammatory response, a key part of the body’s naturally built-in healing processes, intense or long-duration activity sends the immune system into overdrive, temporarily compromising the body’s ability to defend itself.

It’s part of what has been dubbed the “elite athlete paradox” by David Nieman, a professor of health and exercise science and a 2:37 marathon runner based at Appalachian State University. In his own early studies on more than 2000 marathon runners, he discovered that nearly 13% fell ill in the week following a race compared to just 2% of the normal population.

In other research at Loughborough University a few years ago, Professor Mike Gleeson suggested that athletes’ training regime leaves them up to six times more likely to become ill with a virus than a couch potato. Upper-respiratory tract infections (URTIs), acute infections that affect the nose, throat and sinuses, and include the common cold, tonsillitis, sinusitis and flu, are particularly prevalent.

“The heavy training loads of endurance athletes make them more susceptible to URTIs and this is an issue for them as infections can mean missing training sessions or underperforming in competitions,” Professor Gleeson reported.

Immune boosting diet

In the IOC document, nutrition was considered a key factor in the prevention of training-related illnesses and, as we head towards the winter months when viruses and infections become more widespread, now is the time to prepare your diet accordingly. Here’s what is recommended:

Eat carbs: Consume carbohydrate during and after exercise and try to take in both carbohydrate and protein after exercise as it will aid recovery and ease the load on the body as it recuperates

Get vitamin D: Measure and monitor your vitamin D status (you can get a blood test from your GP) and use a supplement if required. Vitamin D is an important part of the immune system. Some studies have shown that there is a link between vitamin D levels and the risk of getting a respiratory infection.

Prepare with a probiotic: Consider taking a probiotic supplement such as lactobacillus probiotics on a daily basis. Numerous studies have shown the beneficial bacteria provide an immunity boost. One trial, published in the Journal of Science and Medicine in Sport, found that athletes had about 40% fewer colds and gastrointestinal infections when they took a probiotic compared to when they took a placebo.

Polyphenol pick-me-up: Consuming more fruit and plant-based foods will ensure you get high levels of antioxidants, but also consider taking polyphenol supplements, like quercetin (try Healthspan Elite Quercetin with Green Tea; £24.95 for 90 supplements from healthspan.co.uk).

Take zinc lozenges: Popping 75mg zinc a day at the onset of upper respiratory symptoms has been shown in some trials to reduce the number of days with illness. A review of 15 studies with 1360 participants by the group Cochrane, an international collaboration of researchers that reviews evidence behind therapeutic interventions, found that taking zinc lozenges or syrup within 24 hours of a cold appearing appeared to shorten the duration of the virus by about a day.

Avoid alcohol: Even small amounts can impair immune function for several hours, particularly after strenuous training or competition and, the more you drink the worse the effects. Last year, researchers from the University of Maryland and Loyola University revealed how a single episode of heavy drinking significantly weakens the body’s immune system. Blood tests on young people who had been drinking revealed that levels of infection-fighting white blood cells plummeted when they were tested two hours and five hours after consuming alcohol. According to the study, published in the journal Alcohol, levels of a type of protein called cytokines that tell the immune system to become less active were also higher after post-alcohol drinking episodes.

Keep clean: Wash hands regularly and effectively with soap and water especially before meals and after direct contact with anything potentially contagious – that’s people, animals, blood, secretions, public places and bathrooms. Carry insect antimicrobial foam or cream or alcohol-based hand-washing gel with you to restaurants and even friends’ houses. Be prepared.

» Wendy Martinson OBE is a registered dietitian and performance nutritionist who has worked with elite athletes in many sports. She was sports nutritionist for Team GB at the 2008 Beijing Olympic Games and is a consultant for Healthspan (healthspan.co.uk)