Most people know someone who’s had cancer: a family member, a friend, a loved one. Who gets it can sometimes seem random. But there are many things you can do to reduce your risk.
Cancer can start almost anywhere in the body. Normally, your cells grow and divide to form new cells as the body needs them. When a cell is old or becomes damaged, it dies. Then a new cell takes its place.
But when cancer develops, this orderly process breaks down. Cancer cells divide without stopping. They can then spread into surrounding tissues or other parts of the body.
Cancer starts with damage to the genesSegments of DNA that contain instructions for building the molecules that make the body work. that control the way cells function. Many things you’re exposed to over your lifetime can damage genes. These include chemicals, radiation, tobacco, alcohol, and others. Your body has ways to repair the damage, but they don’t always work perfectly.
As you age, your body has had more time to build up damage. And the normal aging process causes other changes in cells that help cancer develop. These factors make cancer more likely to appear as you age.
“Fortunately, most cancers do not develop as a result of a single exposure,” explains NIH researcher Dr. Erikka Loftfield, who studies cancer prevention. “Typically, you don’t have just one cause for a given cancer. And some potential risk factors, like cigarette smoking and diet, are changeable.”
Because damage to your genes builds up slowly over time, there are many opportunities for prevention.
“Not smoking, maintaining a healthy weight, getting enough physical activity, limiting alcohol, and eating a nutritious diet are all intertwined in cancer prevention,” Loftfield says. “These are all things that also help us live a healthy life.”
Tobacco use is the leading cause of cancer in the U.S. This includes smoking and use of other tobacco products, like chewing tobacco. Many chemicals in tobacco products can damage your genes.
“Smoking is one of the the most dangerous health behaviors there is,” says Dr. Johannes Thrul, a tobacco researcher at Johns Hopkins University.
Using tobacco also increases your risk of heart attack, stroke, lung disease, and many other conditions. But it can be very hard to stop—even if you know the risks.
Tobacco products contain an addictive substance called nicotine. But there are medications that can help you quit. They can reduce nicotine withdrawal and cravings. Some are available by prescription. Others can be found over-the-counter, like nicotine replacement gums or patches. Using medications with counseling can be even more effective.
Thrul and others are looking for new ways to help people quit smoking. They’re developing smartphone apps that track when smokers are close to places that trigger nicotine cravings. The apps then send personalized support messages.
“We’re trying to deliver support to smokers in these critical situations, in real time,” he says.
These apps are still being tested. You can get free help now by visiting smokefree.gov, calling 1-800-QUIT-NOW (1-800-784-8669), or by texting QUIT to 47848.
“No matter how long you’ve smoked, no matter how old you are, quitting smoking will always benefit your health,” Thrul says.
When it comes to cancer prevention, the saying “you are what you eat” applies, says NIH researcher Dr. Jill Reedy, who studies diet and cancer. But it’s not just diet. Your overall lifestyle—including weight and physical activity—also matters.
“There’s a lot of evidence that maintaining a healthy lifestyle has the potential to reduce cancer risk,” Reedy says.
Diet and related factors can raise your risk in many ways. For example, excess weight can increase inflammationHeat, swelling, and redness caused by the body’s protective response to injury or infection. in the body, Reedy explains. Long-term inflammation is thought to increase cancer risk.
Excess weight can also cause the levels of certain hormonesSubstances sent through the bloodstream to signal another part of the body to grow or react a certain way. to rise. High levels of these hormones can raise the risk of some types of cancer, such as breast cancer.
How diet itself affects cancer risk is complicated, Reedy explains. What we eat gets broken down and used by our cells to keep the body running. Chemicals in some foods—like highly processed meats—may raise the risk of cancer. But overall, there aren’t many single foods to avoid.
Other chemicals in food may lower your risk. But no single food, nutrient, or vitamin alone can protect you from cancer. “It would be great if there was a magic bullet, but there isn’t,” Reedy says.
“It’s really about the overall quality of your diet. Choose fruits and vegetables, whole grains, lean proteins, and healthy oils. Limit alcohol, added sugars, saturated fats, and sodium,” she explains.
You can learn more about healthy eating patterns from the Dietary Guidelines for Americans. Healthy eating appears to reduce cancer risk even if you have trouble losing weight, Loftfield explains. And the same seems to be true for physical activity.
“We’ve seen that physical activity lowers the risk of some types of cancers, independent of its effects on weight,” she says. This may be because exercise can reduce inflammation, stress, and other things that can harm your cells.
Loftfield and Reedy are studying new ways to measure what happens in the body after eating different types of foods. This will help them learn more about how diet impacts cancer risk.
There are other simple actions you can take to reduce your risk of specific cancers. To lower your chances of skin cancer, wear sunscreen and sun protective clothing, limit your time in the sun, and avoid tanning beds.
Certain vaccines can reduce your risk of cervical, liver, and other cancers. This is because some viruses, like human papillomavirus (HPV), can damage your genes in ways that lead to cancer.
“Getting vaccinated against HPV and other cancer-related viruses is a very practical way to modify your cancer risk,” Loftfield says.
Common screening tests can also reduce your risk. These let doctors find and remove small growths that may turn into cancer. A colonoscopy, which looks for growths in the colon and rectum, is one example. Cervical cancer screening is another. For tips on talking about your risk for cancers, see the Ask Your Doctor box.