Lifestyle Factors

This article describes in a practical and non-technical way how lifestyle factors affect risk and early detection of cancer.  There are many factors that contribute to the formation of cancer.  More simplistic diseases rely on perhaps one or two factors such as an infectious agent and a susceptible host.  Cancer is an extremely diverse disease and comes about when a number of factors come together. 

Some of the conditions that must happen for a cancer to develop are

1) defective or absent DNA repair mechanism,

2) some blockade of the immune system or natural killer cells to prevent cancer cell destruction,

3) loss of cell growth regulation, and often

4) damage to one or two key genes in a cell that do not have a redundant “back-up” helper.

Our body’s cells undergo some form of damage all the time and repair mechanisms and surveillance systems help to regulate cancer formation and either prevent or destroy it.  This is why cancers are much more frequent in people with weak or absent immune system functions such as someone with AIDS complex or medication induced immunosuppression from transplantation-assisting medications.

Damage to cells that might lead to cancer can occur spontaneously or via some type of injury.  Substances that cause injury to cells that might lead to cancer are called carcinogens.  Some carcinogens require much exposure to and others cause damage with relatively low doses of exposure.  The most common carcinogen in our society is the chemicals contained in cigarette smoke.  Sunlight is a carcinogen but can be taken in modest levels and is also a part of health by assisting vitamin D function and our overall mood.  Some risk factors are modifiable and others non-modifiable.  Having several relatives with breast cancer increases your risk for breast cancer and is a non-modifiable risk factor.  Smoking 3 packs of cigarettes a day is a modifiable risk factor.  Having several relatives with lung cancer and smoking heavily is an example of having both modifiable and non-modifiable risk factors.

Examples of how the commonest cancers are affected by various lifestyle habits. 

The commonest cancers in the United States are breast cancer, prostate cancer, colon cancer, lung cancer, endometrial cancer and bladder cancer.  The commonest causes of death from cancer include lung cancer, colon cancer, prostate cancer, breast cancer and pancreatic cancer.

Colon cancer: Modifiable lifestyle factors associated with the risk of colon cancer include a low fiber diet, diet lacking or very low in fruits and vegetables, heavy alcohol or smoking abuse, obesity and an inactive lifestyle (i.e. lack of exercise).  The reasons why these are risk factors are complex.  Some of these risk factors are just associations and some are likely a direct cause and effect.  The mutations that must happen to cause colon cancer occur along a cascade of genes and are a part of the “adenoma-carcinoma” sequence.  Losing some weight or getting close to the ideal body weight is a helpful step.  Avoiding tobacco use all together and minimizing alcohol intake will help decrease risk.  The diet is probably the biggest contributor.  A diet that is low in fiber and high in fat causes a long transit time for stool in the colon.  This is theorized to provide more contact time with potentially harmful breakdown products of digestion.

Breast Cancer: Modifiable lifestyle risk factors for breast cancer include later age at first birth, not breastfeeding, never giving birth, obesity, extended use of hormone replacement therapy, and not getting regular exercise.  The major lifestyle risk factors for breast cancer all have the common factor extended exposure to higher levels of estrogen in the blood.  The family planning factors which really should be done according to your goals and life-planning are known risk factors but not meant to be something that is done in order to decrease breast cancer risk.  The major modifiable risks that are practical to alter include minimizing or avoiding estrogen hormone supplements, exercise and achieving a healthy body weight.

Lung Cancer: Despite being well known and the number one cancer killer, cigarette smoking remains the most common modifiable lifestyle risk factor.  In order to effectively decrease this risk factor, more aggressive policy at a national level may be needed.  The morbidity, mortality and cost to society from cigarette smoking is enormous.  Even if someone has smoked for many years, they will still get immediate benefit in terms of less decrease in lung function and lowering cancer risk by stopping smoking.

Prostate Cancer: There are no specific lifestyle alternations that are known to definitely alter the risk of prostate cancer.  General recommendations such as not smoking and achieving a healthy weight are practical.

Pancreas Cancer:  Several risk factors for pancreas cancer have been identified.  The most conclusive risk factor with the best evidence is cigarette smoking.  Having many episodes of pancreatitis may increase the risk of pancreatic cancer.  A major factor in most pancreatitis is alcohol abuse.  Certainly to maintain a healthy pancreas avoiding alcohol abuse is important.  Whether or not this will prevent pancreas cancer is unknown but it is an important part of overall long-term pancreas health.  A diet low in fruits and vegetables may contribute as well.

Hopefully a pattern is noticeable as many of the measures that help prevent one cancer will help prevent others as well.  As an additional benefit, avoiding smoking and achieving a healthy body weight contributes to a healthy heart.

REFERENCES:

  1. Carey WD. (2010) Cleveland Clinic: Current Clinical Medicine, 2nd ed. Section 14.  Cleveland, OH: Saunders.
  2. Abeloff, M.D. (2008). Abeloff: Abeloff’sClinical  Oncology, 4th ed. Chapter 26. Philadelphia, PA: Churchill Livingstone – Elsevier
  3. www.cdc.gov/cancer/colorectal/basic_info/risk_factors.htm
  4. www.cdc.gov/cancer/breast/basic_info/risk_factors.htm
  5. www.cdc.gov/cancer/prostate/basic_info/risk_factors.htm
  6. This article was originally published on September 3, 2012 and last revision and update was 9/4/2015.