Cancer prevention and risk factors

Spectrum Health Cancer Center wants to help you take action to lower your chances of getting cancer. By preventing cancer altogether, we can reduce the burden of cancer and lower the number of deaths caused by cancer.

Cancer is not a single disease but a group of related diseases. Many things in our genes and lifestyle, and the environment around us may increase or decrease our risk of getting cancer. 

There are many different ways to help prevent cancer, including:

  • Avoid or control things known to cause cancer
  • Changes in lifestyle and diet
  • Regular health screening
  • Finding precancerous conditions early (Precancerous conditions are conditions that may become cancer)

What causes cancer?

Each cell in our body contains genes that guide the way the body grows, develops and repairs itself. There are many genes that control whether a cell lives or dies, divides (multiplies) or takes on special functions, such as becoming a nerve cell or a muscle cell.

Changes (mutations) in genes can cause normal controls in cells to break down. When this happens, cells do not die when they should and new cells are produced when the body does not need them. The buildup of extra cells may cause a mass (tumor) to form. Tumors can be benign or malignant (cancerous). Malignant tumor cells invade nearby tissues and spread to other parts of the body. Benign tumor cells do not invade nearby tissues or spread.

Cancer Risk Factors

A cancer risk factor is anything that increases your chances of developing cancer. A cancer protective factor is anything that deceases your chances of developing cancer. Some risk factors for cancer can be avoided, but many cannot. For example, both smoking and inheriting certain genes are risk factors for some types of cancer, but only smoking can be avoided.

Risk Factors

The following factors are known to increase or affect the risk of cancer:

Cigarette Smoking and Tobacco Use

Tobacco use is strongly linked to an increased risk for many kinds of cancer. Experts believe that cigarette smoking causes about 30% of all cancer deaths in the United States. Not smoking or quitting smoking lowers the risk of getting cancer and dying from cancer.


Certain viruses and bacteria are able to cause cancer. Viruses and other infection-causing agents cause more cases of cancer in the developing world (about 1 in 4 cases of cancer) than in developed nations (less than 1 in 10 cases of cancer). Examples of cancer-causing viruses and bacteria include:

  • Human papillomavirus (HPV) increases the risk for cancers of the cervix, penis, vagina, anus, and oropharynx
  • Hepatitis B and hepatitis C viruses increase the risk for liver cancer
  • Epstein-Barr virus increases the risk for Burkitt lymphoma
  • Helicobacter pylori increases the risk for gastric cancer

Two vaccines to prevent infection by cancer-causing agents have already been developed and approved by the U.S. Food and Drug Administration (FDA). One is a vaccine to prevent infection with hepatitis B virus. The other protects against infection with strains of human papillomavirus (HPV) that cause cervical cancer. Scientists continue to work on vaccines against infections that cause cancer.


The foods that you eat on a regular basis make up your diet. Diet is being studied as a risk factor for cancer. It is hard to study the effects of diet on cancer because a person’s diet includes foods that may protect against cancer and foods that may increase the risk of cancer.

Some studies show that fruits and non-starchy vegetables may protect against cancers of the mouth, esophagus, and stomach. Fruits may also protect against lung cancer.

Some studies have shown that a diet high in fat, proteins, calories, and red meat increases the risk of colorectal cancer, but other studies have not shown this.

It is not known if a diet low in fat and high in fiber, fruits, and vegetables lowers the risk of colorectal cancer.


Drinking alcohol is linked to an increased risk of many types of cancer. To minimize risk, limit alcohol consumption to two drinks per day for men and one drink per day for women.

Physical Activity

Studies show that people who are physically active have a lower risk of certain cancers than those who are not. It is not known if physical activity itself is the reason for this.

Studies show a strong link between physical activity and a lower risk of colorectal cancer. Some studies show that physical activity protects against postmenopausal breast cancer and endometrial cancer.


Studies show that obesity is linked to a higher risk of multiple types of cancer. It is not known if losing weight lowers the risk of cancers that have been linked to obesity.

Environmental Risk Factors

Being exposed to chemicals and other substances in the environment has been linked to some cancers:

  • Links between air pollution and cancer risk have been found. These include links between lung cancer and secondhand tobacco smoke, outdoor air pollution and asbestos
  • Drinking water that contains a large amount of arsenic has been linked to skin, bladder and lung cancers 

Studies are ongoing to see if pesticides and other pollutants increase the risk of cancer.

Interventions Known to Lower Cancer Risk

An intervention is a treatment or action taken to prevent or treat disease, or improve health in other ways. Many studies are being done to find ways to keep cancer from starting or recurring (coming back).


Chemoprevention is the use of substances to lower the risk of cancer, or keep it from recurring. The substances may be natural or man-made. Some chemopreventive agents are tested in people who are at high risk for a certain type of cancer. The risk may be because of a precancerous condition, family history or lifestyle factors. 

Some chemoprevention studies have shown good results. For example, selective estrogen receptor modulators (SERMS) such as tamoxifen or raloxifene have been shown to reduce the risk of breast cancer in women at high risk. Finasteride and dutasteride have been shown to reduce the risk of prostate cancer.

Chemoprevention agents that are being studied in clinical trials include COX-2 inhibitors. They are being studied for the prevention of colorectal and breast cancer. Aspirin is being studied for the prevention of colorectal cancer.

Interventions Not Known to Cancer Risk

There is not enough proof that taking multivitamin and mineral supplements or single vitamins or minerals can prevent cancer. Many vitamins and mineral supplements have been studied, but have not been shown to lower the risk of cancer.

The Selenium and Vitamin E Cancer Prevention Trial (SELECT) found that vitamin E taken alone increased the risk of prostate cancer. The risk continued even after the men stopped taking vitamin E. Taking selenium with vitamin E or taking selenium alone did not increase the risk of prostate cancer. 

Vitamin D has also been studied to see if it has anticancer effects. Skin exposed to sunshine can make vitamin D. Vitamin D can also be consumed in the diet and in dietary supplements. Taking vitamin D in doses from 400-1100 IU / day has not been shown to lower or increase the risk of cancer. 

The VITamin D and OmegA-3 TriaL (VITAL) is under way to study whether taking vitamin D (2000 IU/ day) and omega-3 fatty acids from marine (oily fish) sources lowers the risk of cancer.

Research and Clinical Trials

Joining a research study may involve risks. Those risks vary from study to study. You should understand what risks are anticipated in the study you are considering and remember that there can be unanticipated risks. The risks should be clearly explained in the consent form.

Sometimes the person who joins a research study will benefit directly, and their disease or problem will be helped. However, the possibility of receiving benefit varies from study to study, just like the risks. It is important to remember that the main goal of research is to collect information that may help you and future patients. You should always ask questions and keep asking until you understand how the research study is different from the treatment you would get outside of the research study.

A Powerful Second Opinion

If you have been diagnosed with cancer and would like a consultation or second opinion.