With winter around the corner it is time to stoke up your immune system by consuming the right foods, says Peta Bee

Have you turned on the central heating yet? If not, it won’t be long before the thermostat is cranked up and stuffy indoor conditions combined with hard training give rise to winter viruses.

Athletes are more prone than most to upper respiratory tract infections (URTI) at this time of year and symptoms of a sore throat, headache, fatigue, runny nose and watery eyes account for 40-60% of problems that sideline them from training.

Your diet is your best defence against seasonal infection, so prepare for battle by adding the following to your shopping list:


As a member of the cruciferous family of vegetables (cabbage, cauliflower and kale are siblings), broccoli has a lot going for it in terms of illness prevention. For starters, it has the most sizeable amount of sulforaphane, a potent compound that helps to boost the body’s protective enzymes.

Aim for at least 50g broccoli, kale or Brussels sprouts daily to obtain a beneficial intake. Green smoothies are a great way to boost your sulforaphane supplies – you can even buy broccoli powder to add to the mix.


Used for centuries as a health aid in South Africa, Rooibos – Africaans for red bush – is said to help treat everything from hay fever and asthma to eczema and nausea. It’s caffeine-free and contains plentiful antioxidants and small amounts of minerals including calcium, potassium, iron, zinc and magnesium.

Studies at universities in Japan and South Africa have found that the tea’s antioxidant profile helps to boost the body’s immune system and the onset of cellular damage.


Sports scientists are beginning to understand more fully the mechanisms by which a healthy gut flora enhances performances.

A study published in the journal Nutrients last year explained how a daily probiotic supplement can boost immunity against URTI by enhancing levels of good gut bacteria. Researchers gave 33 athletes either a daily dose of a probiotic supplement or a placebo and asked them to continue with their intense training for 12 weeks. By the end of the trial, the placebo athletes had 11% lower post-exercise levels of tryptophan, an amino acid that plays a role in controlling immune responses, compared to levels at the start of the study. Levels were unchanged in the probiotic group who were also 2.2 times less likely to suffer one or more URTI symptoms during the three months.


Matcha is a favourite of athletes. Made from ground-up green tea leaves it is rich in polyphenol compounds called catechins, a type of antioxidant. Some studies have shown matcha provides three times the amount of polyphenols as regular green tea – because it is powdered you’re consuming the leaves as opposed to infusing them in water and then discarding them.

Sprinkle it on your porridge or add to smoothies.


This fermented dairy milk product – pronounced Keff-er and meaning ‘feel good’ in Turkish – has an acquired taste that’s not initially to everyone’s liking. But persevere as it is good for boosting gut bacteria, bone health and warding off winter infections.

“It has a much wider range of bacteria than yoghurt,” says Dr Megan Rossi, a nutrition research associate at King’s College London and a gut health specialist. One trial found that consuming kefir for six months improved markers of bone health in a group with osteoporosis and there are suggestions it also has anti-inflammatory properties, Rossi says.


Taking mega-doses of this vitamin is not recommended for the general population, yet anyone training hard should consider it.

In trials at the University of Helsinki more than 11,000 marathon runners, teenage competitive swimmers, soldiers and school children were given a dose of the vitamin before assessing its impact on their health.

While it had no effect on the sedentary participants, the researchers showed it halved the risk of catching a cold in athletes training hard. Among the group of teenage swimmers who caught a cold and were treated with vitamin C, most shook off their illness twice as fast as training partners who didn’t take it. In the youngest athletes a daily 1g dose slashed the average duration of colds in children by 18% and in adults by 8%.