The American Cancer Society recommends that people at average risk of colorectal cancer begin routine screening at age 50. The most common screening method is a colonoscopy to check for masses and remove polyps that may be pre-cancerous. Colorectal cancer is the third most common cancer in the US, and with recent trends showing more and more patients being diagnosed in their 20s, it’s clear that colorectal cancer isn’t just a concern for senior citizens. The overall rates of colorectal cancer have been falling since 1998, but there’s been an uptick in rates among patients 20 to 34 years old. Though the overall rate of colorectal cancer is still low in younger populations (9 out of 10 diagnoses still occur in patients 50 or older), researchers are eager to understand the trend and reverse it.
While an exact cause hasn’t been pinpointed, there are aspects of the typical American diet and lifestyle that have been shown to increase patients’ risk, and the American Institute for Cancer Research has recently released a new report which estimates that lifestyle changes could prevent 47% of colorectal cancers in the US. The report takes into account worldwide research on colorectal cancer risk, analyzing 99 studies and including data on 29 million people (a quarter of a million of whom were diagnosed with colorectal cancer). The lifestyle changes found to reduce risk were increased physical activity and whole grain intake. Risk factors that increased risk were consumption of alcohol, red meat, and processed meats. Obesity also increased cancer risk.
Americans’ consumption of whole grains, such as breads made with whole-wheat flour and brown rice, has increased in the last decade but still falls woefully short of the US Dietary Guidelines, which recommend that half of all grains consumed be whole grains. In the average US household, whole grains are a fraction of total grain consumption. The new report concludes for the first time that eating more whole grains lowers your colorectal cancer risk independent of other factors. People who ate an average of three servings of whole grains daily had about a 17% reduced risk.
Physical activity decreased cancer risk as well, though it only seemed to reduce the risk of colon cancer and had no impact on the incidence of rectal cancer. Only one in three adults receive the recommended amount of physical activity each week, and less than 5% engage in at least 30 minutes of physical activity each day.
It was also found that processed meats like bacon and hot dogs increase the risk of colorectal cancer. About 50 grams of processed meat a day (about one hot dog) was linked to a 16% increase in risk, and the more you eat, the greater your risk. Other factors that increased risk included eating more than 18 oz. of red meat (beef or pork) each week, consuming an average of two or more alcoholic drinks per day, and obesity. (Excess weight also increases your risk for a host of other cancers, offering a powerful incentive to try to maintain a healthy weight whenever possible.)
The report also found less conclusive associations between risk and lifestyle choices. It’s possible that low intake of fruits and vegetables increase cancer risk, especially for those eating less than a cup of each per day. Fish and foods high in vitamin C may also reduce your risk of colorectal cancer. Of course, there are no guarantees when it comes to cancer, but we know that a healthy lifestyle that includes physical activity and a plant-based diet lowers your risk not only of colorectal cancer but of other cancers, heart disease, and obesity. As research continues to reveal links between lifestyle factors and disease, we should feel empowered. Though lifestyle changes can be challenging, these findings show that many of us can improve our long-term health by making healthy choices on a daily basis.
According to Edward L Giovannucci, MD, ScD, lead author of the report and professor of nutrition and epidemiology at the Harvard TH Chan School of Public Health, “Many of the ways to help prevent colorectal cancer are important for overall health. Factors such as maintaining a lean body weight, proper exercise, limiting red and processed meat and eating more whole grains and fiber would lower risk substantially. Moreover, limiting alcohol to at most two drinks per day and avoidance or cessation of smoking also lower risk.” He concludes that “the findings from this comprehensive report are robust and clear: Diet and lifestyle have a major role in colorectal cancer.”