Cycling is great exercise, but while it seems healthy is it damaging your prostate health? This essential guide to cycling and prostate health was written by Professor Robert Thomas, of Addenbrook's, Cambridge.
Whether commuting, having fun with kids, being a weekend warrior in a grueling sportif or holiday tours in the alps, cycling is an excellent way to increase physical activity. Middle-aged men in Lycra (MAMILs), in particular, spend millions of pounds on bikes and gadgets; but is this increasingly popular hobby damaging their health?
Crashing or being run over aside, the potential health issues specific to cycling relate to the cellular damage caused by intense regimens and the direct trauma to the perineum (the area between the anus and the scrotum) from the saddle. These are said to be responsible for an increased incidence of erectile dysfunction, infertility, waterworks problems, osteoporosis and prostate cancer but are these data genuine and even if they are, do they supersede the positive health benefit of exercise?
By enthusing more people to exercise, cycling should certainly be applauded. Regular exercise lowers the risk of heart disease, stroke, dementia, obesity, diabetes and cancer itself [Thomas]. A recent review in the British Journal of Sports Medicine highlighted the biochemical beneficial changes which happen after exercise including reducing inflammation, improving immunity and insulin sensitivity [Thomas]. Another study reported that exercise improves skin tone, mental activity and slows our biological ticking clocks embedded in our DNA (telomere length) [Ornish]. Many cyclists therefore argue that they are likely to be more radiant, intelligent and biologically younger than their sedentary counterparts.
Prostate Cancer
There have been reports of an increased risk of prostate cancer but please don’t stop cycling, as the evidence for this not strong. The largest study, involving 5,000 cyclists, reported a six-fold increase among cyclists who trained more than 8 hours compared to men who trained less than 3.75 hours a week [Hollingworth]. What was less widely highlighted in the media was that all men in the study had a prostate risk rate, which was 3 times less than the general population. So overall there is less prostate cancer in cyclists compared to sedentary men.
Nevertheless, the increased risk in elite athletes compared to other cyclists is probably genuine so it is worth considering some practical nutritional strategies which can mitigate the potential risks, ameliorate the overall benefits of cycling and at the same time, enhance sports performance. The most important issues are now highlighted:
Energy production and oxidative stress
A vast amount of energy is required to fuel the muscles during intensive and prolonged aerobic regimens. It's important to keep levels of sugar in the blood stream as constant as possible during exercise. Processed sugar is therefore not an ideal source of energy as this creates peaks in blood sugar levels leading to excess insulin and then hypoglycaemia. Complex carbohydrates are better as these are slowly broken down to glucose and fats which are broken down further to glycerol and fatty acids. All these feed into the three biochemical pathways of the energy production pathways namely; glycolysis, the Kreb's cycle and oxidative phosphorylation (OXPHOS). As cycling is an aerobic sport, for the majority of the time the tissues are well oxygenated so OXPHOS, which requires oxygen to convert food into ATP fuel packets, is the preferred and most efficient pathway. A by-product of OXPHOS, however, is the formation of reactive oxidative species (ROS) that can damage DNA and other cellular structures. The state of ‘high level of ROS’ is known as oxidative stress and, if this occurs in the chondritic cells of the joints, it leads to arthritis, in muscle cells’ poor recovery and, for all cells, to premature aging and genetic mutations thus leading to cancer. In order to minimise oxidative stress it's necessary to consider two fundamental issues.
1. Supporting antioxidant enzymes: The building blocks for the antioxidant enzymes, most influenced by nutrition, are essential minerals, vitamins and polyphenols. Deficiencies in essential nutrients should be avoided particularly zinc, copper and selenium which are required for one of the main enzymes, superoxide dismutase. That said, studies have also shown that over correcting levels of minerals and vitamins do not confer additional advantages. Of more concern, excess vitamin A, Vitamin E with selenium could actually increase the prostate cancer risk [Klein]. Putting these nutrients into a supplement is therefore not recommended unless the individual has had a micronutrient blood test (see cancernet.co.uk) revealing a specific deficiency which requires correction. Otherwise, the best way to avoid deficiencies is with a varied diet rich in seafood, including oysters, clams and fish as well as nuts and leafy green vegetables.
Likewise, cyclists should boost their diet with polyphenol-rich foods, which promote antioxidant enzyme production, such as dark green vegetables, spices, herbs, teas, berries, nuts, colourful vegetables and fruits [Thomas]. The World Cancer Research Fund reported that individuals who eat these foods have a lower risk of cancer and well conducted trials of polyphenol- rich whole food supplements have demonstrated significant benefits. The largest, and most notable of these, was the UK government backed national Pomi-T trial which showed that a supplement containing a blend of purified, high grade turmeric, pomegranate, green tea and broccoli prevented early prostate cancer progressing to more advanced disease in a large proportion of men compared to those taking a placebo [Thomas]. Whole food supplements, such as this, are a logical choice for cyclists, as part of a balanced diet, as higher levels of polyphenol intake not only potentially reduce the damage from free radicals generated by energy production, their anti-inflammatory effects can counterbalance the repeated trauma from the saddle. Furthermore, polyphenols are essential for tissue repair including joints, helping to maintain joint health. Finally, the nitrates in these foods are also beneficial for cyclists as they are converted to nitric oxide. This relaxes smooth muscles around arteries enhancing blood to tissues improving oxygenation muscle and heart recovery, erectile function, cognitive function and lowering blood pressure.
2. Avoiding carcinogens and pro-inflammatory toxins: In addition to unaccustomed or strenuous exercise factors that increase oxidative stress include excess chronic inflammation caused by obesity, processed sugar intake, acrylamides formed by super heating carbohydrates (crisps and even some cereal and energy bars); and Polycyclic Aromatic Hydrocarbons and Heterocyclic Amines found in processed and burnt meats.
Low testosterone, infertility and erectile dysfunction
Although regular exercise delays the natural age-related decline in testosterone, strenuous exercise, accelerates this drift. This is because after intense exercise, testosterone increases for about an hour depending the level of fitness and age but in response the body then adapts by telling the testes to reduce production [kraemer]. A fall in testosterone levels in the long term, can contributing to fatigue, poor motivation, reduced erythropoietin levels leading to anaemia, low libido and erectile dysfunction (ED). In addition, pressure to the perineum can damage the adjacent nerves and blood vessels supplying the penis, which can ameliorate ED. The level of ED is, however, debatable with some arguing that cyclists are more motivated by thoughts of their next ride rather than their "next ride" – excuse the pun. Some studies, such as the large UK cyclist survey, reporting no problems with ED but others such as the Boston cohort study reporting it was three times more likely especially among cyclists who use saddles which cause penile numbness. In women, repeated friction can lead to vaginitis, soreness, bacterial and yeast infections.
In terms of infertility, the combination of ROS and lower testosterone explains the increased number of abnormal sperms and lower viable sperm counts amoung elite cyclists, although an effect on actual fertility has not been established [Leibovitch].
Measures to help maintain testosterone levels.
Low levels of vitamin D, zinc, magnesium selenium and chromium are associated with a lower levels of testosterone [Prasad]. Reassuringly, the same studies showed that correcting these deficiencies increased testosterone back to normal and can also improve muscle strength [Cinar,Grimaldi]. Cholesterol is a precursor in the testosterone biosynthesis pathway so increase healthy fat intake, preferably from plant sources such as coconut, avocado and olive oil as well as smaller oily fish such as mackerel, sardines and anchovies. Avoid statins unless you have other risk factors for cardiac disease as these lower testosterone [Wang]. Eat less processed sugar and refined carbohydrates as these increase blood sugar and risk type two diabetes which is linked to lower testosterone. Consider less refined carbohydrates which have higher protein content such as wild rice and quinoa.
Osteoporosis
Lower testosterone combined with a general lower body mass index of cyclists and lack of weight-bearing when exercising leads to significant loss of calcium in the bones (osteoporosis) [Nagle]. This was so severe for the professional cyclist Chris Boardman that he had to quit the sport aged 32 years. Adopting the measures to maintain testosterone are important particularly Vitamin D supplementation in the winter and sensible sun exposure (avoiding sun burn) at other times [Nemptsch].
It would also be sensible to introduce a weight-bearing exercise, such as jogging or squatting with weights, into training regimens. Protein from plants rather than meats, is better for bone health, so increase intake of whole soy, chickpeas, lentils and beans [Beasley]. A very large recent study also reported higher intake of green tea with better bone health [Thomas].
Go to: Complete overview on Prostate cancer - symptoms, causes and treatment alternatives
In conclusion, the biochemical changes, which arise after exercise, including cycling, have significant cancer and chronic disease protection properties. Nevertheless, the generation of free radicals, fall in testosterone and local inflammation remain potential concerns with intense cycling. Some simple dietary changes can help maintain testosterone levels and bone density and adopting a healthy polyphenol-rich diet would be very sensible practice.
Professor Robert Thomas
Consultant Oncologist Bedford and Addenbrooke’s Cambridge University
Hospitals
Professor of Biological & Exercise Science, University of Bedfordshire
Author of Keep-Healthy after cancer
Email: [email protected] Web: cancernet.co.uk.
Twitter: @cancernetUK
Facebook.com/cancernetuk
Blog.cancernet.co.uk
References:
- Hollingworth M (2014). Erectile dysfunction & prostate cancer in cyclists: J Men Health;11:75-9.
- Leibovitch I (2005). The vicious cycling related urogenital disorders. Eur Urol; 47:277-87.
- Thomas R (2017). The biochemistry of exercise. BJSM 2017;51:640-644.
- Thomas R (2015). Phytochemicals in cancer prevention and management. BJMP; 8 (2)
- Thomas R (2014). The UK National Pomi-T study. Prostate Cancer & Diseases 7, 180-6
- Kraemer W. Hormonal responses and adaptions to exercise Sports Med. 2005;35(4)339-61.
- Nagle K. systemic review of bone Health in Cyclists. Sports Health. 2011;3(3): 235–43.
- Ornish D (2013). Effect of comprehensive lifestyle changes on telomerase activity and telomere length. The Lancet oncology;14(11):1112-1120.
- Nimptsch (2012). Association between plasma 25-OH vitamin D and testosterone levels in men. Clinical Endocrinology, 2012 77(1), 106-12
- Wang C. (2005). Low-Fat High-Fiber Diet Decreased Serum and Urine Androgens in Men. Journal of Clinical Endocrinology & Metabolism, 90(6), 3550-3559.
- Grimaldi A (2013). 25(OH) Vitamin D Is Associated with Greater Muscle Strength in Healthy Men and Women. Medicine & Science in Sports & Exercise, 45(1), 157-162.
- Prasad, A. (1996). Zinc status and serum testosterone levels in adults. Nutrition, 12(5), 344-348.
- Cinar V. (2010). Effects of Magnesium on Testosterone Levels of Athletes and Sedentary Subjects at Rest and after Exhaustion. Biological Trace Element Research, 140(1), 18-23.
- Kraemer W (2013). The effects of soy and whey protein supplementation on acute hormonal reponses to resistance exercise in men. Journal of the Am Col Nutrition, 32(1), 66-74.
- Peters E (2001). Vitamin C Supplementation Attenuates the Increases in Circulating Cortisol, Adrenaline and Anti-Inflammatory Polypeptides Following Ultramarathon Running. International Journal of Sports Medicine, 22(7), 537-543.
- Klein E. (2011). Vitamin E and the risk of Prostate cancer. The selenium and vitamin E cancer prevention Trial (SELECT). JAMA 306(14) 1549-56
- Ubajaka C (2015). Males sex hormones and diabetes Niger J Med;24(2):162-8
- Beasley J (2010) Protein intake and bone mineral density. Am J Clin Nutr.91(5): 1311–16.