The sport also preserves muscle and helps maintains stable levels of body fat and cholesterol.
Scientists carried out tests on 125 amateur cyclists aged 55 to 79 and compared them with healthy adults from a wide age group who did not exercise regularly.
The findings, outlined in two papers in the journal Aging Cell, showed that the cyclists preserved muscle mass and strength with age while maintaining stable levels of body fat and cholesterol. In men, testosterone levels remained high.
More surprisingly, the anti-ageing effects of cycling appeared to extend to the immune system.
An organ called the thymus, which makes immune cells called T-cells, normally starts to shrink from the age of 20. But the thymuses of older cyclists were found to be generating as many T-cells as those of young people.
Prof Janet Lord, director of the Institute of Inflammation and Ageing at the University of Birmingham, said: “Hippocrates in 400BC said that exercise is man’s best medicine, but his message has been lost over time and we are an increasingly sedentary society.
“However, importantly, our findings debunk the assumption that ageing automatically makes us more frail. Our research means we now have strong evidence that encouraging people to commit to regular exercise throughout their lives is a viable solution to the problem that we are living longer but not healthier.”
Male cyclists taking part in the study had to be able to cycle 100km in under 6.5 hours, while women had to cover 60km in 5.5 hours.
The non-exercising group consisted of 75 healthy people aged 57 to 80 and 55 young adults aged 20 to 36.
Many other studies have also shown the remarkable health benefits of cycling. A study published in the BMJ last April found that regular cycling cut the risk of death from all causes by more than 40%, and cut the risk of cancer and heart disease by 45%.
Experts also believe cycling boosts riders’ mental health, with multiple studies finding that those who commute by bicycle are happier and less prone to depression than those who use any other form of transport.
A recent report from cycling and walking charity Sustrans also found that cycling does not just benefit an individual’s health but that of society as a whole, estimating that if Britain were to reach government targets for walking and cycling, the country would save about £9.3bn and reduce deaths from air pollution by more than 13,000 over the next decade.
Prof Stephen Harridge, director of the Centre of Human & Aerospace Physiological Sciences at King’s College London, said: “The findings emphasise the fact that the cyclists do not exercise because they are healthy, but that they are healthy because they have been exercising for such a large proportion of their lives.
“Their bodies have been allowed to age optimally, free from the problems usually caused by inactivity. Remove the activity and their health would likely deteriorate.”