Can Diet and Exercise Help Prevent Cancer?
It's not a secret that obesity is a risk factor for many chronic illnesses, including cancer. But what about diet and exercise? Excess weight puts people at risk for cancer, but it takes more than being overweight to cause the disease. For diet and exercise to be protective against cancer, they have to defend against enough obesity-related cancers to make up for any additional cancers associated with an unhealthy lifestyle. That is the logic behind a new study, which found no such protective effect for either diet or exercise on most cancers analyzed.
The study analyzed data from 47 studies that looked at diet and exercise and cancer incidence in people over a period of 17 years. It looked at all types of cancer, including breast, colorectal, lung, prostate and others. "What we found was pretty consistent across all types of cancers -- including common cancers such as colorectal cancer in both men and women," said first author Michael Pollak, M.D., M.P.H., an associate professor of medicine at the University of Southern California's Keck School of Medicine in Los Angeles [emphasis added] . "There were five or six cancers that we found to be statistically significant, and they all involved excess body weight." [emphasis added] More specifically, the researchers found no significant associations between excess body weight and cancer incidence from diet or exercise.
"Our findings cast considerable doubt on the value of either dietary counseling or exercise as preventive measures in reducing cancer risk," Pollak said. Both diet and exercise have been proposed as potentially effective ways to reduce cancer risk because they can reduce weight and improve overall health. But only about 8% of adults in the United States are physically active, according to one CDC estimate. And nearly half a billion dollars is spent each year in the U.S. on dietary advice alone, according to the American Institute for Cancer Research. "Certainly there are a lot of people who believe that dietary changes can affect cancer risk. But our findings suggest that these programs may not be doing much," said Pollak. The results were published online in the Journal of the National Cancer Institute on July 8.
Michael Pollak, M.D., M.P.H., an associate professor of medicine at the University of Southern California's Keck School of Medicine and his colleagues looked at data from 47 cancer studies related to diet and exercise, each involving more than 100,000 subjects over an average of 20 years or more. They identified 13 diet studies and 11 exercise studies that met their criteria. The data in these studies were adjusted for smoking, physical activity and other established risk factors.
The researchers found no significant associations between excess body weight and cancer incidence in any of the 13 diet or 11 exercise studies.
"Our findings cast considerable doubt on the value of either dietary counseling or exercise as preventive measures in reducing cancer risk," Pollak said. Both diet and exercise have been proposed as potentially effective ways to reduce cancer risk because they can reduce weight, but only about 8% of adults are physically active, according to one CDC estimate. And nearly half a billion dollars is spent each year in the U.S. on dietary advice alone, according to the American Institute for Cancer Research.
"Certainly there are a lot of people who believe that dietary changes can affect cancer risk. But our findings suggest that these programs may not be doing much," Pollak added
The researchers also looked at all types of cancer, including breast, colorectal, lung, prostate and others. None of these associations were statistically significant in any of the 11 diet or exercise studies for a total of about 1,200 cancers examined overall.
Both diet and exercise have been proposed as potentially effective ways to reduce cancer risk because they can reduce weight and improve overall health. But only about 8% of adults in the United States are physically active, according to one CDC estimate. And nearly half a billion dollars is spent each year in the U.S. on dietary advice alone, according to the American Institute for Cancer Research. "Certainly there are a lot of people who believe that dietary changes can affect cancer risk," Pollak said. "But our findings suggest that these programs may not be doing much."
For more information: Cancer Facts & Figures 2013 . American Cancer Society. http://www.cancer.org/cancer/cancercauses/othercauses/dietandexercise.html E-mail: michaelpollak@med.usc.edu Phone: 818-604-6189 Subscribe to the Journal of the National Cancer Institute, a publication of the American Association for Cancer Research.
Cancer Facts & Figures 2013
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Cancer Facts & Figures 2013 by American Cancer Society http://www.cancer.org/research/cancercauses/factsheet/overview#tostate
Over the course of a lifetime there are more than 1.7 million new cancer diagnoses and over 600,000 deaths from the disease. Cancer facts & figures 2013 by American Cancer Society is designed to bring awareness to those living with cancer as well as those who care about them. The report also addresses the most commonly diagnosed forms of cancer in the United States with state-specific information where it is available.
The report is organized by type of cancer, region of the country, age & gender and presents data on incidence, mortality, and survival rates as well as risk factors for each type of cancer. In addition to updated statistics about new cases and deaths from 10 common cancers in 2012, it includes state-by-state estimates for colorectal, breast, lung & bronchus, and prostate cancers.
• The most commonly diagnosed forms of cancer are prostate (232K), breast (224K), lung (162K), colon & rectum (135K) and melanoma (75K).
• Lung cancer is the leading cause of cancer death among both men and women.
• More than 1.7 million new cases of cancer will be diagnosed in 2013 and more than 580,000 people will die from the disease.
• Cancer is the second leading cause of death in the U.S., following only heart diseases (for all races combined). Among children ages 1 to 14 years, birth defects are the number one cause of death.
For people who have survived cancer, its impact doesn't end at survival statistics; it's measured in how they live their lives every day-with hope, courage, and a relentless spirit for life.
Conclusion: There are significant limitations in this study and a high potential for bias error for diagnosis of cancer. There is not sufficient data to draw conclusions about the relationship between cancer incidence and obesity.
Reference: Cancer Facts & Figures 2013 by American Cancer Society http://www.cancer.org/research/cancercauses/factsheet/overview#tostate
This report was designed to take information relevant to improving our understanding of the genetic causes of cancer in 2013 and provide a clear view of what kind of progress has been made in that time. The report provides detailed statistics about cancer, including the incidence, mortality, and survival rates for all forms of cancer, as well as risk factors for each form of cancer.