Physical fitness can help curb the frequency and severity of colds, according to new research.

Researchers from North Carolina, US, published their findings in the British Journal of Sports Medicine, and claim that not only do fitter people get fewer colds, they also get milder ones.

The study looked at 1,000 adults up to the age of 85, whose respiratory health was tracked for 12 weeks during the autumn and winter of 2008.

Six out of 10 participants were women, and four out of 10 were aged between 18 and 39; 40 per cent were middle aged, and one in four were aged 60 and older.

Participants reported back on how frequently they took aerobic exercise and rated their fitness levels using a 10-point system. They were also asked about other factors that can affect immune system response, such as lifestyle, diet and recent stressful events.

The number of days with symptoms among those who said they were physically active on five or more days of the week and felt fit was almost half (43 per cent to 46 per cent less) that of those who exercised on only one or fewer days of the week.

The severity of symptoms fell by 41 per cent among those who felt the fittest and by 31 per cent among those who were the most active.