There is no way to prevent cancer with 100 percent certainty, but there are several ways to significantly reduce your risk of developing it.

Quit Smoking

In addition to lung cancer, smoking tobacco is known to cause cancers of the mouth, throat, larynx, esophagus, stomach, pancreas, kidney, bladder, and cervix. Scientists estimate that 30 percent of all cancer deaths in the U.S. are due to smoking. Secondhand smoke, the smoke that nonsmokers are exposed to by being around smokers, is also known to increase the risk of cancer.

Although smokers who quit do not reduce their cancer risk to the level of someone who has never smoked, quitting still helps. According to the National Cancer Institute, people who stop smoking before age 30 have a 90 percent lower risk of dying due to smoking-related disease (such as lung cancer, emphysema, and chronic bronchitis), and those who quit before age 50 have a 50 percent lower risk.

Avoid Carcinogens

A carcinogen is a chemical known to cause cancer. Cigarette smoke, discussed above, contains more than 50 carcinogens. Other carcinogens include:

  • Asbestos
  • Benzene
  • Cadmium
  • Nickel
  • Radon
  • Uranium
  • Vinyl chloride

Minimize Exposure to UV and Other Radiation

Ultraviolet (UV) radiation from the sun (and tanning beds) can damage the DNA of skin cells and cause skin cancer. When going out in the sun, always take precautions to protect yourself by wearing a hat, sunglasses, and clothing that covers most of your skin, or by applying sunscreen frequently. Learn more about UV rays, SPF, and the most affective sunscreens.

Other forms of radiation—such as high levels of radon (a radioactive gas) in your home and medical tests that use radiation (x-rays, CT scans)—can also cause cancer. To avoid unnecessary exposure to radiation, test your home for radon (find simple, inexpensive test kits at hardware stores), and avoid excessive x-rays and similar tests when possible.

Eat Healthy and Exercise

Studies have shown that a diet high in fat and red and processed meats increases the risk of colon, prostate, and other cancers. Excessive alcohol consumption—more than one drink per day for women and two per day for men—is also linked to cancers of the mouth, esophagus, and liver. On the other hand, a diet rich in fruits, vegetables, and whole grains has been found to decrease the risk of digestive system, lung, and other cancers.

Exercising regularly can also lower your cancer risk. Adults who get at least 2.5 hours of moderate intensity physical activity per week lower their risk of colon cancer by a third compared to those who do not exercise.

Obesity and Cancer

A combination of good food choices and exercise helps to achieve and maintain a healthy weight. These lifestyle habits help reduce the risk of cancer (and other diseases such as heart disease and diabetes). Studies have shown that being overweight or obese can increase your risk of breast, colon, esophageal, kidney, gallbladder, and uterine cancers.

Get Tested

Routine cancer tests do not prevent cancer from developing, but they do allow cancers to be detected early, which greatly improves a patient's prognosis. The American Cancer Society recommends regular screenings for the following:

Breast Cancer

There has been a recent controversy regarding when women should begin regular screenings for breast cancer. The American Cancer Society (ACS) recommends annual mammograms starting at age 40. The U.S. Preventive Services Task Force (USPSTF) recommends that women between the ages of 50 and 74 years should have a screening mammogram every other year to check for breast cancer. Talk to your doctor about the right screening plan for you.

Cervical Cancer

The ACS recommends that women begin cervical cancer screening three years after their first vaginal intercourse but no later than 21 years of age, after which they should be screened every year if they are sexually active. Women between ages 30 and 65 whose previous pap smears have been normal should have the test done every three years.

Prostate Cancer

The ACS is less definitive about prostate cancer screening, stating that men should "make informed decisions with their doctor about whether to be tested." This is due to the lack of research to prove that the potential benefits of screening outweigh the harms of testing and treatment. Men who are 50 years of age should discuss the pros and cons of screening. Those at a higher risk of prostate cancer—such as African-American men or men with a family history of prostate cancer—should start talk to their doctors at age 45.

Colorectal Cancer

There are several tests to screen for colorectal cancer and/or polyps. According to the ACS, women and men over the age of 50 should have an annual fecal occult blood test, which screens for cancer. Other recommended tests that screen for cancer and polyps include a flexible sigmoidoscopy (recommended every five years), a colonoscopy (every 10 years), a double-contrast barium enema (ever 5 years), or a CT colonography (every 5 years). Talk to your doctor about which tests and screening schedule is right for you.

Get Vaccinated

HPV

Some types of human papillomavirus (HPV) can infect the genital area; in fact, genital HPV is the most common sexually transmitted infection. Certain types of HPV can cause genital warts, while other types can cause cervical cancer. A vaccine against HPV called Gardasil has been approved by the FDA and is recommended for all girls and women between ages 9 and 26.

Hepatitis B

Hepatitis B virus causes inflammation of the liver, potentially resulting in serious liver disease including chronic infection, scarring, and cancer. According to the Centers for Disease Control and Prevention (CDC), children should get their first dose of the vaccine—usually given in a series of three or four shots—at birth and should have complete the vaccine by 6 to 18 months of age. It is recommended for anybody under age 18 who did not get the vaccine at birth and for unvaccinated adults at higher risk for the disease.

The vaccine is not recommended for anyone severely allergic to baker's yeast or other components of the vaccine. Those are ill or who have had a previous severe allergic reaction to the vaccine should not be vaccinated.