Although some believe that certain people are destined to get cancer and nothing can be done to change their fate, that's just not the case, experts say.
Even people who have genes that predispose them to certain types of cancer might be able to reduce their risk by living a healthy lifestyle, they say.
"Between 27 and 49 percent of people think preventing cancer is impossible or highly unlikely," said Karen Collins, a registered dietitian and a nutrition adviser for the American Institute for Cancer Research.
But, she said, the institute has identified three steps people could take to dramatically affect the chances of developing cancer:
- Eat a mostly plant-based diet.
- Maintain a healthy weight.
- Exercise regularly.
"The data is pretty clear that we can make a significant drop in the cancer rate with these three changes," Collins said. "We can prevent about one-third of cancers with these changes. And if you add tobacco prevention, which reduces about 30 percent of cancers, over half of today's cancers could be prevented."
Dr. Virginia Kaklamani, an oncologist who specializes in breast cancer at Northwestern Memorial Hospital in Chicago, added that "increased weight increases the risk of cancer, and physical activity, regardless of weight, decreases breast cancer risk."
The institute joined with the World Cancer Research Fund to release a report, Food, Nutrition, Physical Activity and the Prevention of Cancer: A Global Perspective, that was prepared by a team of international researchers who reviewed more than 7,000 studies on cancer.
Their recommendations included:
- Weight: Maintain a body mass index (BMI) between 21 and 23 and avoid gaining weight during adulthood. Although a BMI of up to 24.9 is considered normal, the lower end of normal is better for cancer prevention, the report said.
- Exercise: Participate in moderate activity -- brisk walking or something equivalent -- for at least 30 minutes a day. Ideally, though, people are advised to work up to 60 minutes of moderate exercise daily, or 30 minutes of vigorous exercise. The report also advised limiting sedentary activities, such as TV-watching.
- Diet: Eat healthily. That means a diet that consists of mostly plant-based foods, such as fruits, vegetables and whole grains. The experts recommended avoiding sugary, processed foods and fast foods as much as possible and limiting red meat consumption to no more than 18 ounces a week. Salt consumption should also be restricted to no more than 2.4 grams of salt daily. And, the report advised, limit alcohol consumption to one drink a day for women and two drinks a day for men.
- Supplements: Don't rely on them. The cancer-preventing benefits derived from nutrients are believed to come from foods, not from individual supplements.
But Collins stressed that people need to realize that the recommendations weren't an "all or nothing" proposition.
"Some people feel, 'I'm so far away from a healthy weight that I'll never get there, so why try?' " she said. "But every drop toward a healthy weight is a good move, and it's worth it."
And, she said, each healthy change someone makes tends to support another one. "When you're active and at a healthy weight, eating choices become clear, because good foods tend to give you more energy to be physically active," she said.