Why did Sir Chris Hoy get prostate cancer? Was the Olympic champion's condition caused by cycling

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Sir Chris Hoy has revealed his terminal cancer diagnosis - oncologist Professor Robert Thomas looks into whether cycling could be to blame.

Cycling is a splendid form of exercise, but some studies are suggesting there may be a risk to the prostate among extreme cyclists and Sir Hoy would certainly come into that category. The prostate, which lies in the lower pelvis, is subject to pressure and repeated minor trauma during a long cycle ride, which can cause inflammation.

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Some published research has reported that over time, chronic inflammation can trigger prostate problems, including cancer. Although the conclusions of these studies remain debatable, strong interest in this issue is justified as prostate cancer is now the most common cancer in men (more than 42,000 new cases each year), and even if the link is partially true, it will affect a lot of men.

First of all, it must be emphasized that regular exercise is very healthy, and by motivating more people to become physically active, cycling should be applauded. It is firmly established that men and women who exercise vigorously for more than 2-3 hours a week have a lower risk of obesity, hypertension, raised cholesterol, type two diabetes, hence gaining protection from the biggest killers, including cancer, heart disease, dementia, and stroke.

An evidence review published in the British Journal of Sports Medicine confirmed that cycling outdoors helps maintain vitamin D levels and circadian rhythm, which boosts mood, enhances sleep patterns, lowers daytime fatigue, and improves motivation at home and work. 

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It is true that the PSA can go up after a vigorous bike ride, so it's not recommended to go for the blood test within 48 hours of a ride. However, with all these multiple benefits of exercise, it is not surprising that there are some doubts about the reliability of the data suggesting cycling is harmful to the prostate. These studies rely on self-reported observations rather than independent prospective robust data, so they are open to significant bias. Even if the correlation is true, a linkage also does not prove causation as other factors can affect the data. 

Great Britain's Sir Chris Hoy celebrating winning the Gold Medal in the Men's Sprint Final at the Track Cycling Course at the Laoshan Velodrome during the 2008 Beijing Olympic Games in ChinaGreat Britain's Sir Chris Hoy celebrating winning the Gold Medal in the Men's Sprint Final at the Track Cycling Course at the Laoshan Velodrome during the 2008 Beijing Olympic Games in China
Great Britain's Sir Chris Hoy celebrating winning the Gold Medal in the Men's Sprint Final at the Track Cycling Course at the Laoshan Velodrome during the 2008 Beijing Olympic Games in China | Andrew Milligan/PA Wire

The most highlighted study involved a survey of more than 5000 cyclists, which recorded cycling frequency and history of cancer. They found a six-fold increase in prostate cancer in men among extreme cyclists (more than eight hours training a week) compared to those who trained less than four hours. This triggered headlines such as "Cycling causes prostate cancer," but what the newspapers chose to omit, or failed to understand, was that there was only a 1.7% incidence of prostate in both groups - at least three times lower than the incidence in the general population of men of similar ages.

So the answers to the question whether Sir Hoy's cancer was caused by his cycling is "probably not"  but as he was an athlete with a history of such intense training and races, so there remains a possibility. 

How could cycling affect the prostate?

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This increase in prostate cancer in extreme cyclists does have some scientific explanations. As mentioned above, the proximity of the prostate to the saddle can result in repeated minor trauma, which can cause inflammation. Inflammation causes cell to turn over faster, increasing the risk of spontaneous mutations in the DNA. It also reduces the time cells have to repair themselves. In addition, intense or unaccustomed exercise generates large quantities of free radicals which are a by-product of energy production. Free radicals can damage DNA, further increasing the risk of causing mutations - these are the first stage in cancer initiation and progression. 

How cyclists can reduce prostate cancer risks

Graduated training programmes increase antioxidant enzyme production which mop up these free radicals. It's also important to eat a lot of phytochemical-rich foods such as green tea, turmeric, pomegranate, broccoli, cranberries, ginger nuts, herbs, and spices which enhance antioxidant enzyme formation and protect the DNA from free radicals.

Phytochemicals also have direct anti-inflammatory, gut health enhancing and direct anti-cancer properties. They also improve mood, help muscle recovery, and protect joints, making exercise more comfortable and productive. Minerals such as zinc, magnesium and selenium are also needed for anti-oxidant enzyme production so its important to maintain adequate dietary intake with pumpkins seed and shell fish or even a well balanced mineral supplement around intense training.

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Healthy "good" bacteria help reduce inflammation in the gut improving absorption of minerals and vitamins and enhancing sports performance. Their positive effect on immunity was highlighted in studies of athletes given lactobacillus probiotics who then had fewer breaks in their training programmes from colds and flu. People with a healthy gut microbiome have lower inflammation in their whole body including their prostate.

Strategies to improve gut health, include quitting smoking, lowering alcohol and processed sugar intake; eating healthy probiotic bacteria rich foods such as kimchi, kefir and sauerkraut as well as prebiotic high fibre foods such as in beans, mushrooms, herbs and vegetables. Probiotic supplements have a role and studies have shown that blends combining lactobacillus a prebiotic and vitamin D are particularly relevant for prostate health which is why they were used, in combination with phytochemical rich supplements in the latest national anti-prostate cancer nutritional intervention study.

In conclusion, first of all, don’t stop cycling, the data actually shows that moderate cycling reduces prostate cancer risk. However, the generation of free radicals and increased prostate inflammation remain potential concerns with intense cycling. Investing in a prostate-protecting saddle and adopting dietary changes will reduce this risk and enhance performance and overall wellbeing. In particular, boosting phytochemical-rich foods, enhancing gut health, avoiding vitamin D and mineral deficiencies.

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