Men who eat plenty of plant foods, stay a healthy weight, and follow more of AICR’s Cancer Prevention Recommendations have a lower risk of developing colorectal cancer compared to men who follow fewer of them, according to a new study that suggests possible gender differences in lifestyle factors and risk of this cancer.
The study was published in Cancer Epidemiology, Biomarkers & Prevention.
It adds to a wide body of independent research showing that following AICR’s Cancer Prevention Recommendations really do prevent cancer. You can read about some of that research here.
Looking at lifestyle and risk:
In the latest study researchers wanted to better understand how AICR’s three major guidelines around diet, activity and weight holistically connected to lower colorectal cancer risk. To do this, they first scored how closely almost 115,000 men and women followed seven of the AICR’s recommendations focused on these lifestyle factors.
Participants, who were part of the Nurses’ Health Study and the Health Professionals Follow-up Study, had regularly answered questions about their eating, activity, and other lifestyle habits from 1986 to 2012.
People were assigned either one point, half a point or zero points for each recommendation, depending upon how closely they adhered to it. Some of the recommendations were split into their components then summed. Take AICR’s recommendation to be a healthy weight, for example; the study scored BMI, waist circumference, and avoiding weight gain – measured by whether the person gained ten pounds in the previous decade. Ultimately, these scores were calculated to give each person one possible point for each of the three main groups: diet, weight, and physical activity. Adding them together gave a lifestyle score, ranging from 0 to 3.
After 24 years, there were 2,449 diagnosed cases of colorectal cancer. Men who most adhered to AICR’s lifestyle recommendations had a 36 percent lower risk of colorectal cancer compared with those who least followed them. This is after accounting for age, smoking, family history and other recognized colorectal cancer risks. Interestingly, the results among women pointed to a reduced risk but were weaker.
When the researchers analyzed the diet recommendations alone, there was still an association with lower colorectal cancer risk although not as strong. Again, this association with lower risk was weaker among women.
The observed differences between genders needs more study, notes the paper. It may possibly be explained by the role of body fat, which makes up a third of the calculated lifestyle score. “Higher adiposity has been observed to be much more strongly associated with colorectal cancer in men in several studies,” said lead investigator Joshua Petimar, ScD, of the Harvard T.H. Chan School of Public Health. “The reason for this isn’t entirely clear, but it is suspected that estrogen plays a part because estrogen is produced by adipose tissue.”
The study also hinted that for women, having too much body fat as a young adult might play a role in later colorectal cancer risk. It’s important to note that this finding could be due to chance, notes Petimar, but it also supports some previous research. “While the mechanism for this is unclear, it is worth investigating whether improving lifestyle from young adulthood to late adulthood is most important for colorectal cancer risk in women,” the authors write.
Like all long-term population studies that investigate lifestyle factors, this study may have measurement errors with diet, physical activity, sedentary behavior, weight and waist circumference. Another limitation includes the population itself, which primarily consisted of white health professionals. This study needs to be repeated in non-white and non-U.S. populations, the study concludes.
Preventing many common cancers
Colorectal cancer is only one of the common cancers linked to lifestyle factors. AICR research shows that diet, activity and being a healthy weight can lower the risk of many other cancers, including those of the breast, endometrium and liver. Aside from not smoking, a strong body of research shows that staying a healthy weight throughout life is the single most important step both men and women can take to reduce cancer risk.
AICR’s Cancer Prevention Recommendations are drawn from a global analysis of the evidence. You can read more about how to lower colorectal cancer risk from our latest Continuous Update report.
The study authors are supported by grants from The National Heart, Lung, and Blood Institute and National Cancer Institute.