Harvard researchers find as many as 40 percent of cancer cases, and half of cancer deaths, come down to things people could easily change.
Many Americans often worry about whether chemicals, pollution or other factors out of their control cause cancer, but a new analysis shows otherwise: people are firmly in charge of much of their own risk of cancer. As we get older, our risk goes up, which could come from doing the same bad habits over a long period of time. The same can be said for being diagnosed with diabetes and prediabetes. Eating one large order of French fries will not increase your risk for cancer or diabetes, but eating two orders a week over 40 years would be over 4,000 orders, or over 2,000,000 calories and 259,000 carbohydrates, which can certainly be injurious to your health.
The team at Harvard Medical School calculated that 20 to 40 percent of cancer cases, and half of cancer deaths, could be prevented if people quit smoking, avoided heavy drinking, kept a healthy weight, and got just a half hour a day of moderate exercise. They used data from long-term studies of about 140,000 health professionals who update researchers on their health every two years for the analysis, published in the Journal of the American Medical Association’s JAMA Oncology.
“Not surprisingly, these figures increased to 40 percent to 70 percent when assessed with regard to the broader U.S. population of whites, which has a much worse lifestyle pattern than our cohorts,” wrote Dr. Edward Giovannucci of Harvard Medical School. The analysis was simple. They broke the 140,000 people into two groups: those with a healthy lifestyle, and everyone else. The healthy lifestyle definition was based on a large body of studies that have shown what personal habits are linked with higher or lower risks of cancer. They include not smoking; drinking no more than one drink a day for women, two drinks a day for men; keeping a healthy weight, defined as body mass index of between a very slender 18.5 and a slightly overweight 27.5; and getting the equivalent of just over an hour of vigorous exercise or two and a half hours of moderate exercise a week.
Heavy drinking raises colon, breast, liver and head and neck cancer rates. Obesity raises the risk of esophageal, colon, pancreatic and other cancers. Smoking causes 80 to 90 percent of lung cancer deaths. Only about 28,000 of the people analyzed qualified as following a healthy lifestyle. When the rates of cancer in their group were compared to rates in the rest of the volunteers, the differences were clear.
The purpose of the study was to estimate the proportion of cases and deaths of carcinoma (all cancers except skin, brain, lymphatic, hematologic, and nonfatal prostate malignancies) among whites in the United States that can be potentially prevented by lifestyle modification.The incidence rates of cancer were 463 per 100,000 for women in the “healthy” group, versus 618 per 100,000 for those not meeting the healthy goals. For men, it was 283 per 100,000 who met the healthy lifestyle goals versus 425 among those who did not. And these were health professionals, who should at least try to be healthier. When Giovannucci compared the healthy group to the general, white, U.S. public, the differences were even bigger. Plus, they didn’t add in other known factors, such as eating a healthy diet rich in fruits and vegetables, although they said those who followed the other healthy patterns did tend to eat better, also.
“These compelling data together with the findings of the current study provide strong support for the argument that a large proportion of cancers are due to environmental factors and can be prevented by lifestyle modification.” By “environmental,” they mean non-genetic causes. To a scientist, environment includes diet, exercise and other factors.
89,571 women and 46,339 men from 2 cohorts were included in the study: 16,531 women and 11,731 men had a healthy lifestyle pattern (low-risk group), and the remaining 73,040 women and 34,608 men made up the high-risk group. Within the 2 cohorts, the PARs for incidence and mortality of total carcinoma were 25% and 48% in women, and 33% and 44% in men, respectively. For individual cancers, the respective PARs in women and men were 82% and 78% for lung, 29% and 20% for colon and rectum, 30% and 29% for pancreas, and 36% and 44% for bladder. Similar estimates were obtained for mortality. The PARs were 4% and 12% for breast cancer incidence and mortality, and 21% for fatal prostate cancer. Substantially higher PARs were obtained when the low-risk group was compared with the US population. For example, the PARs in women and men were 41% and 63% for incidence of total carcinoma, and 60% and 59% for colorectal cancer, respectively.
From the results, it was concluded that a substantial cancer burden may be prevented through lifestyle modification. Primary prevention should remain a priority for cancer control.
- 89,571 women and 46,339 men from 2 cohorts were included in the study.
- Many cancer cases and even more deaths among U.S. white individuals might be prevented by quitting smoking, avoiding heavy alcohol consumption, maintaining a BMI between 18.5 and 27.5, and exercising at a moderate intensity for at least 150 minutes or at a vigorous intensity for at least 75 minutes every week.
- These compelling data together with the findings of the current study provide strong support for the argument that a large proportion of cancers are due to environmental factors and can be prevented by lifestyle modification.
Preventable Incidence and Mortality of Carcinoma Associated With Lifestyle Factors Among White Adults in the United States. May 19, 2016. doi:10.1001/jamaoncol.2016.0843.