People who undertake moderate or vigorous physical activity are at a lower risk
of developing several cancers, especially lung and colorectal, but also those of the
breast, endometrium (lining of the uterus), and advanced forms of prostate cancer.
A study of more than 49,000 patients over nearly eight years found that those in
the highest fitness category decreased the odds of developing lung cancer by 77%
and decreased the risk of developing colorectal cancer by 61% compared to those
who were the least fit. Among those diagnosed with lung and colorectal cancer,
over the eight years, those with high fitness decreased the risk of subsequent death
from lung cancer by 44% and from colorectal cancer by 89%.

Information on the association of physical activity with the incidence of common
types of cancer comes from a 2016 meta-analysis of data from 12 prospective U.S.
and European cohorts with self-reported physical activity. The study compared
moderate to vigorous intensity leisure-time physical activity with the incidence of
26 types of cancer among a total of 1.44 million study participants. The ratio of risk
(Hazard Ratio) of developing a cancer for individuals with high vs. low levels of
leisure-time physical activity was found to be lower among those with high physical
activity for 13 cancers:

• Esophageal adenocarcinoma (Hazard Ratio 0.58)
• Liver (HR 0.73)
• Lung (HR 0.74)
• Kidney (HR 0.77)
• Gastric cardia (HR 0.78)
• Endometrial (HR 0.79)
• Myeloid leukemia (HR 0.80)
• Myeloma (HR 0.83)
• Colon (HR 0.84)
• Head and neck (HR 0.85)
• Rectal (HR 0.87)
• Bladder (HR 0.87)
• Breast (HR 0.90)

Leisure-time physical activity was associated with 27% higher risks of malignant
melanoma (HR 1.27) and an unexplained and possibly insignificant 5% higher risk
of prostate cancer (HR 1.05). The increased risk of malignant melanoma might be
the result of sun exposure during outdoor physical activity.

Although the amount of physical activity needed to reduce cancer risk is uncertain,
the consensus is that a good starting place is the 2018 Physical Activity Guidelines
Scientific Report recommendation for adults that calls for at least 150 minutes of
moderate-intensity or 75 minutes of vigorous-intensity physical activity each week
or an equivalent combination. Moderate activities include brisk walking, biking, even
housework, and gardening. Vigorous activities make you use large muscle groups,
increase your heart rate, and make you out of breath.

Neither the type or amount of physical activity needed to reduce cancer risk nor
the biological mechanism by which physical activity reduces cancer risk are well
understood. Since physical activity contributes to reaching and staying at a healthy
body weight, avoiding overweight and obesity may be an important way that physical
activity reduces the risk of cancer.

This blog presents opinions and ideas and is intended to provide helpful general information. I am not engaged in rendering advice or services to the individual reader. The ideas, procedures and suggestions in that are presented are not in any way a substitute for the advice and care of the reader’s own physician or other medical professional based on the reader’s own individual conditions, symptoms or concerns. If the reader needs personal medical, health, dietary, exercise or other assistance or advice the reader should consult a physician and/or other qualified health professionals. The author specifically disclaims all responsibility for any injury, damage or loss that the reader may incur as a direct or indirect consequence of following any directions or suggestions given in this blog or participating in any programs described in this blog or in the book, The Building Blocks of Health––How to Optimize Your Health with a Lifestyle Checklist (available in print or downloaded at Amazon, Apple, Barnes and Noble and elsewhere). Copyright 2021 by J. Joseph Speidel