What You Do Matters: Yes, cancer is tied to genes. But diet, stress and other lifestyle factors play a role.

July 13, 2015
Cancer Lifestyle

It seems a day doesn’t go by without some new promise about how specific foods, supplements or lifestyle habits contribute to cancer risk. Much of the information is specious. The fact that you can’t believe everything you read or hear is probably not so surprising, but what may be a little shocking is how much of the lifestyle change message is actually on target.

“Very sound science tells us that up to one-third of cancers in the United States are related to obesity, physical inactivity and poor nutrition,” says surgical oncologist Anton J. Bilchik, MD, PhD, professor of surgery, chief of medicine and chief of the gastrointestinal research program at the John Wayne Cancer Institute. “That suggests that up to one-third of cancer cases can be prevented with lifestyle changes.”

There are, of course, some obvious examples of how choices impact cancer risk. We all know that cigarette smoking is linked to lung cancer. The best way to prevent it is to not smoke. 

Beyond that, though, do you know what to believe and what to ignore? Here are the 10 most important things, besides not smoking, you can do to improve your odds of not getting cancer or a cancer recurrence.


Although there isn’t a direct cause-and-effect equation for most cancers, we know that more than 40,000 cancers a year are attributed to obesity and 15% to 20% of all cancer deaths are related to obesity, says Maggie DiNome, MD, acting director of the Margie Petersen Breast Center at Providence Saint John’s Health Center. Obesity is linked to a range of cancers, including breast, esophageal, colorectal, pancreatic, uterine and prostate.

And weight doesn’t just influence risk. Overweight people treated for cancer are at increased risk for recurrence and mortality when compared to those patients who aren’t overweight.

Because the link is so glaring, in fact, nutritional counseling for patients before, during and after treatment has become increasingly important, explains Svetlana Akoyeva, RD, a Saint John’s registered dietitian. “What we eat effects quality of life, and it is a crucial part of the short-term and long-term treatment plan here.”

Short-term, Svetlana focuses on helping patients through treatment by finding healthy comfort foods that are palatable. For the long term she develops plans for safe weight loss and healthy weight maintenance that focus on nutrient-dense foods such as non-starchy vegetables, fruits, whole grains, plant-based proteins, lean meats and plenty of water.


sun_720x541_72_RGB Experts at the Centers for Disease Control and Prevention say that skin cancer is the most common type of cancer in the United States and that most cases could be prevented. “Preventing this cancer largely boils down to simple steps: Wear proper sun protection every day and keep out of the sun when possible,” says Dr. Bilchik.

That means hats, sunglasses, sun protective clothing and sunscreen with at least SPF 15. Don’t aim to get your vitamin D through sun exposure either. It’s an important nutrient but best obtained through diet or supplements.


runner_720x472_72_RGBA 2011 study published in the journal Exercise Immunology Review concluded that exercise protects against several types of cancer, including colon, breast, endometrial, lung and pancreas. Furthermore, physical activity is linked with a reduction in cancer recurrence, enhanced health outcomes and increased survival. Women who exercised moderately prior to and after breast cancer treatment, for example, had significant improvements in survival and quality of life compared to sedentary women.

How much is enough, though? The general consensus is that adults should engage in 150 minutes of moderate intensity (such as brisk walking) exercise each week. Children and adolescents should get at least an hour each day.

“Exercise is thought to improve energy metabolism and reduce hormones like estrogen and insulin in the blood that may contribute to cancer growth,” says Dr. Bilchik. “We really can’t think of exercise as optional any more. It’s crucial for cancer prevention and treatment.”


In 2007 the World Cancer Research Fund and the American Institute for Cancer Research released recommendations to reduce breast cancer risk. Studies show women who maintained a healthy weight, limited alcohol intake and consumed a plant-based diet reduced their risk for breast cancer by 62%.

“This is the advice I live by,” says Dr. DiNome. “I have a strong family history of cancer myself, and my husband and I are both older parents to twin 5-year-old girls, so I feel a particularly strong responsibility to do whatever I can to reduce my cancer risk.”

Dr. DiNome says she and her husband adopted a vegan diet after their daughters were born. “I find that when I live by what I preach, it’s easier for me to encourage my patients to do the same.“
Besides the breast cancer risk reduction, a study published recently in the journal JAMA Internal Medicine found that vegetarian diets are also linked to a reduction in the risk of colorectal cancer.


While vitamin supplements are extremely popular, Dr. Bilchik says there’s only one supplement he recommends for cancer prevention: vitamin D. “There’s evidence that D may help prevent colon cancer,” he explains. You can get vitamin D through supplements or foods such as salmon, canned tuna, fortified milk or orange juice.


High consumption of dietary fiber is associated with a lower risk of some cancers, particularly esophageal, stomach, colorectal, lung and breast cancers, says Svetlana. “My favorite source of fiber is a variety of non-starchy vegetables. Besides fiber, they are rich with phytochemicals and act as antioxidants to bring health-enhancing effects.”

Fresh fruit, beans, nuts and whole grains are good sources of fiber. The National Cancer Institute recommends 35 grams of fiber a day. Getting fiber through food, rather than supplements, is the best bet.

Here’s a sample of the fiber content of some common foods:

  • One cup of cooked black beans: 15 grams of fiber
  • One cup of blackberries: 7.6 grams
  • One serving of All-Bran cereal: 8.5 grams


Diets that focus on fruits and veggies are most healthful, but if you include moderate amounts of animal protein, there’s a healthier way to do it. Opt for steaming, poaching or stewing.

“Grilling or frying meat at high temperatures forms chemicals that may increase cancer risk, particularly colon cancer risk,” warns Dr. Bilchik.


YogaIllo_720x456_72_RGB A 2004 study published in the journal Psychological Bulletin analyzed the literature of 30 years of research on psychological stress and how it impacts disease. The conclusion: Stress doesn’t cause cancer, yet it may encourage an existing tumor to grow and spread. 

In addition, controlling stress is linked with better quality of life for cancer patients, says Dr. DiNome.

“This is why I’m really excited about the services we offer through the Willow Sage Wellness Program at Saint John’s Health Center. The program was created solely from the fundraising efforts of our community because we believe that nutritional counseling, yoga therapy, massage therapy, mindful meditation and other therapies for stress reduction should be accessible. They are paramount to every patient’s overall care.”


Excessive alcohol consumption means you’re at increased risk for mouth, esophageal, larynx, colon, breast and possibly pancreatic cancer. Alcohol is thought to increase estrogen and other hormones in the blood that may contribute to cancer.

Men should limit alcohol consumption to a maximum of two drinks a day. Women should limit intake to a maximum of one drink a day (one drink equals 12 ounces of beer, 5 ounces of wine or 1.5 ounces of hard liquor).

And needless to say, it’s best not to have a cigarette chaser with that cocktail. “Combining alcohol and tobacco increases the risk far more than either drinking or smoking alone,” warns Dr. Bilchik.


In recent years, misinformation about soy products has led some people to avoid eating tofu and other products. But the best research to date concludes traditional soy products such as tofu, miso, tempeh and soy milk are excellent sources of protein and may even reduce breast cancer risk and recurrence, says Dr. Bilchik.

An analysis sponsored by the California Breast Cancer Research Program and the National Cancer Institute found that soy food intake, in the amount consumed in Asian populations (about 10 to 20 milligrams of isoflavones per day, the equivalent of roughly one-half to one cup of soy milk), was associated with a reduction of breast cancer risk as well as mortality and recurrence among women with breast cancer. Taking soy supplements, however, has not been shown to reduce cancer risk.

For more information on the Cancer Prevention Program at Saint John’s Health Center or to donate to the program, please contact the Office of Development at 310- 315-6111.


Here’s a short list of the strategies Dr. Bilchik tells his patients they can safely ignore:

  • Taking most supplements—The exception is calcium and vitamin D, which is helpful in some patients, particularly women.
  • Drinking black or green tea—Since antioxidants have not been shown to reduce the risk of cancer, the antioxidant claims for these beverages also don’t hold up. If you enjoy the beverage, however, there’s no harm in drinking it.
  • Eliminating trans fats—They elevate levels of low-density lipoprotein cholesterol (the bad kind) and may boost the risk of heart disease, but there’s no data that trans fats increase cancer risk.
  • Eating GMO-free/organic-only food—You may have other reasons to support these foods, but there’s no evidence that GMOs increase the risk of cancer. Furthermore, there’s no evidence to support an organic-only diet for cancer prevention.
  • Banning sweeteners, sugar substitutes and sugar—According to Dr. Bilchik, much research has looked into sugar substitutes and sugar. There’s no evidence that either contributes to cancer risk.