We all know that exercise provides many benefits to us, but when we wake up at 5am to go for a run it is definitely harder to remember this. Hopefully, this new study from the American Cancer Society, the National Cancer Institute, and the Harvard T.H. Chan School of Public Health, will convince you that that morning run (or brisk walk) really is worth it. Health experts have known for a long while that exercise is linked with a lower risk of several cancers, but there has been limited evidence about exactly how much exercise is needed and what exactly the benefits are.

Charles Mathew, PhD, and other researchers conducted the most weightscomprehensive study to date where they examined groups from the US, Europe and Australia, focusing on 15 cancers that had previously found to be associated with physical activity. In total there were 755,459 individuals studied of which 53% were female, who had no history of cancer at the start of follow-up. They analyzed the dose-response relationship between leisure-time physical activity and cancer to provide new insight into the amount of physical activity needed for a reduced risk of many cancer types.

In this study of approximately 750,000 adults, engagement in the recommended amounts of leisure-time physical activity (7.5-15 MET hours/week) described by the Physical Activity Guidelines for Americans Advisory Committee, equivalent to 2.5 to 5.0 hours/week of moderate-intensity activity (eg, brisk walking), was associated with significantly lower risk for breast cancer, colon (men only), endometrial, kidney, myeloma, and liver cancer and non-Hodgkin lymphoma (women only).

People who engaged in at least 2.5 to 5.0 hours of moderate-intensity exercise per week had a statistically significant reduction in risk for breast cancer, colon (men only), endometrial, kidney, myeloma, and liver cancer and non-Hodgkin lymphoma (women only).

Interestingly, the strength of associations for recommended amounts of physical activity versus none ranged from a 6% to 10% lower risk for breast cancer to an 18% to 27% lower risk for liver cancer. The reason that exercise had such a great impact on liver cancer as opposed to breast cancer can be explained by the underlying mechanisms driving the formation of liver cancerous cells. For example, exercise exerts a direct effect on glucose, glycogen, and fat metabolism in the liver and may reduce risk of or reverse nonalcoholic fatty liver disease, which is a risk factor for liver cancer. So if there is a history of liver cancer in your family, or in fact any of these aforementioned cancers, then that 5am wake up may just be worth it!

Cancer prevention is an increasingly important field of research as many cancers still do not have an efficient treatment or therapy available. Therefore, it is important to be aware of the ways in which you can reduce your risk of various cancers. You can find more information at https://www.cancer.org/healthy.html.

Charles E. Matthews, Steven C. Moore, Hannah Arem, Michael B. Cook, Britton Trabert, Niclas Håkansson, Susanna C. Larsson, Alicja Wolk, Susan M. Gapstur, Brigid M. Lynch, Roger L. Milne, Neal D. Freedman, Wen-Yi Huang, Amy Berrington de Gonzalez, Cari M. Kitahara, Martha S. Linet, Eric J. Shiroma, Sven Sandin, Alpa V. Patel, and I-Min Lee. Amount and Intensity of Leisure-Time Physical Activity and Lower Cancer Risk. Journal of Clinical Oncology 2020 38:7, 686-697