The damage to DNA that leads to cancer can occur from a variety of external environmental
causes, including ionizing radiation, exposure to carcinogenic (cancer-
causing) chemicals, and infection with certain viruses and bacteria. Unhealthy
conditions and behaviors, including smoking, alcohol consumption, obesity, an unhealthy diet, and physical inactivity, also increase the risk of cancer. Inheritance of certain genes also increases the risk of cancer.
The American Cancer Society (ACS) estimates that among Americans, as many as
two-thirds of cancers result from things that we can control, with smoking linked to
about one-third of all cancer deaths in the U.S. and another third of cancers linked
to weight, diet, and lack of physical activity.
Some studies suggest a smaller proportion of cancers can be prevented by lifestyle
choices. An article in JAMA Oncology in 2016 estimated the proportion of cases of
cancer and deaths from cancer that could be prevented by a healthy lifestyle based
on data from the Nurses’ Health Study and the Health Professionals Follow-up
Study. Study subjects were considered to be in a low-risk group if they: 1) were
never or past smokers of less than a pack a day for five years; 2) did not drink alcohol
or drank moderately (no more than one drink/day for women, two drinks/day
for men); 3) had a BMI of at least 18.5 but lower than 27.5; and, 4) were physically
active at least 75 vigorous-intensity or 150 moderate-intensity minutes a week. All
others were in a high-risk group.
In the low-risk group, the incidence of cancer was 25% lower for women and 33%
lower for men; and mortality was 48% lower for women and 44% lower for men
than for those in the high-risk group. The study authors concluded that by quitting
smoking, approximately 80% to 90% of lung cancer deaths could be avoided, and
from 10% to 70% of deaths from other specific cancers could be prevented by a
healthy lifestyle. They found that, among the health professionals studied, 20% to
40% of cancer cases, and about half of cancer deaths could be prevented through
lifestyle modification.
A similar study published in the British Journal of Cancer concluded that 40% of
cancers in the U.K. were related to life choices with about half of the preventable
cancers linked to smoking, a quarter of the preventable cases linked to unhealthy
diets, and the remaining preventable cases linked to obesity and alcohol
A 2017 commentary in the New England Journal of Medicine estimated that smoking cessation by age 50 could reduce lung cancer by 62%, cervical cancer screening could bring about 95% reduction of cervical cancers, hepatitis B vaccination could eliminate 95% of liver cancers, estrogen receptor modulators could eliminate about half of the breast cancers among those at high risk, and avoiding obesity could reduce endometrial cancer by about 50%.
An international study estimated the proportion of cancers worldwide that could
be attributed to modifiable risk factors. Of the seven million deaths from cancer
worldwide in 2001, an estimated 2.43 million, or 35%, were attributable to nine
potentially modifiable risk factors: obesity and overweight, low fruit and vegetable
intake, physical inactivity, smoking, alcohol use, unsafe sex, and air pollution.
In high-income countries, such as the U.S., smoking, alcohol use, and overweight and
obesity were the most important factors linked to cancer, and these lifestyle factors
are likely to be the predominant preventable causes of cancer risk for an individual.
With a healthy lifestyle, the risk of getting a cancer will be much lower, but
chance mutations that accumulate with age and cellular replication are likely to be
the greatest proportion of the overall cancer risk.
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
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