5 things you can do today to reduce your risk of colorectal cancer

Hutch News

5 things you can do to reduce your risk of colorectal cancer

Healthy prevention tips from a new data analysis of studies on 29 million adults: move your body, cancer-proof your plate

Sept. 6, 2017

Illustration by Kimberly Carney / Fred Hutch News Service

Cancer can often seem like an arbitrary bombshell that drops out of nowhere and nonchalantly blows up your life. And it’s true: many cancer questions remain unanswered — especially with regard to cause and cure.

But we also have a lot of answers when it comes to reducing your cancer risk. We know definitively that smoking causes a host of cancers. Ditto for smokeless tobacco and environmental hazards like asbestos.

This week we got more news, although it may not seem all that new since a lot of it is advice you’ve heard dozens of times from your doctor — and your mom: Eat less and move more. Finish your vegetables. You’ve had enough alcohol, young lady.

It’s sage advice now borne out by a panel of scientists from the World Cancer Research Fund/American Institute for Cancer Research, an internationally recognized group that includes Dr. Anne McTiernan, a longtime Fred Hutchinson Cancer Research Center epidemiologist who studies the connection between lifestyle and cancer.

So this time you may want to listen, especially if cancer of the large intestine, i.e., the colon, or its lower counterpart, the rectum, is a concern. These cancers, often lumped together under the term colorectal, are the third most common cancers worldwide and the fourth most common cancer killer. Colorectal cancers kill 700,000 people a year globally and here in the U.S., colorectal cancer rates — and deaths from those cancers — are rising in adults under 50.

Fred Hutch's Dr. Anne McTiernan

Fred Hutch cancer prevention researcher Dr. Anne McTiernan was part of an international panel of scientists who just released the latest Continuous Update Project report on Diet, Nutrition, Physical Activity and Colorectal Cancer.

Fred Hutch file photo


“It’s very concerning and needs to be studied,” said McTiernan of the disturbing trend. “Risk factors like obesity and lack of physical activity have caused an increase in diabetes in younger people. Maybe it’s similar in colorectal cancer.”

In their report, McTiernan and her colleagues didn’t address this bump in colorectal cancer rates but they did provide a clear a picture of how the foods we eat and the behaviors we indulge in can either increase or decrease our risk. The team analyzed nearly 100 large cohort studies from around the world involving more than 29 million adults — including nearly 250,000 folks who eventually developed colorectal cancer. Some of those people got cancer as a result of an inherited genetic mutation (think Lynch syndrome); others got it due to disease, like Crohn’s.

But many more developed colorectal cancer because of acquired genetic mutations. It’s these mutations, some of which are brought on by lifestyle choices, that we can actually do something about.

“The findings … are robust and clear,” said lead author Dr. Edward L. Giovannucci, professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health. “Diet and lifestyle have a major role in colorectal cancer.”

Interested in the major role you and your diet can play in fending off colorectal (and maybe even other cancers)? We went through the report with McTiernan, who's written a memoir about her own tumultuous relationship with food, and highlighted five cancer-busting behaviors you can start working on today (check out the full report for additional tips).

Move your body

People who are physically active have a lower risk of colon cancer than those who are not. It doesn’t matter if you move furniture for a living; walk to work and back each day; or hike, bike, swing dance or work out at a gym — it’s all good. Physical activity helps you cut your risk for colon cancer by as much as 20 percent (the numbers weren’t as significant for rectal cancer).

What difference does exercise make? Obesity is a risk factor for many diseases, including cancer. Exercise helps you lose weight, which in turn reduces insulin resistance and inflammation, both of which are linked to the development of tumors in the colon. Exercise may help also specifically cut the risk for colon cancer by stimulating digestion and reducing what’s known as “colon transit time.” And that’s a good thing.

McTiernan said the U.S. Surgeon General’s recommendation of 30 minutes of moderate-intensity activity five days a week is a good starting point.

“But you’ll get more benefit if you do an hour a day,” she said. “You don’t have to run an hour a day. Just fold activity into the day wherever you can: take the stairs instead of elevators; go for a walk at lunch; do walking meetings with colleagues at work.”

Gobble those grains

People who eat whole grains every day have a lower risk of colorectal cancer than people who don’t. In fact, eating about three servings of whole grains (90 grams) per day reduces your risk of colorectal cancer by 17 percent, according to the report. And the more whole grains you eat, the more you cut your risk.

Why? Whole grains contain dietary fiber, which reduces colorectal cancer risk in a number of ways, including, yes, reducing colon "transit time." They also contain a slew of nutrients and compounds with anti-carcinogenic properties, many of which are found in the bran and germ of the grain, i.e., the part that’s processed out.

Oatmeal, popcorn, corn, wild rice, buckwheat and quinoa are all whole grains. Ditto for barley, bulgur, kasha, millet, sorghum and farro. Want some easy swaps to get started? Go with brown rice instead of white and use whole wheat flour instead of refined white flour. And read those labels!

“Look for whole grains as the first ingredient on a package,” McTiernan said. “In general, real food that you make yourself is better than buying everything processed. But that doesn’t mean everybody has to make their own bread.”

“It’s very concerning and nobody knows why,” said McTiernan. “Risk factors like obesity and lack of physical activity have caused an increase in diabetes in younger people. Maybe it’s similar in colorectal cancer.”

McTiernan and her colleagues didn’t address this bump in colorectal cancer rates in their report but did get a clear a picture of how the foods we eat and the behaviors we indulge in can either increase or decrease our risk. The team analyzed nearly 100 large cohort studies from around the world involving more than 29 million adults — including nearly 250,000 folks who eventually developed colorectal cancer. Some of those people got cancer as a result of an inherited genetic mutation (think Lynch syndrome); others got it due to disease, like Crohn’s.

But many more developed colorectal cancer because of acquired genetic mutations. And it’s these mutations, some of which are driven by lifestyle choices, that we can actually do something about. 

Back away from the bacon (and other red/processed meat)

Yes, we know. You love bacon. But it doesn’t love you back. In fact, the report found “consistent evidence” that for every 50 grams of processed, preserved or cured meat eaten per day — that’s about two slices of bacon, by the way — you’re bumping up your risk for colorectal cancer by 16 percent.

Eating red meat — i.e., beef, pork, lamb and goat – also ups your risk, particularly if you eat more than 500 grams in a week (that’s just over a pound).

Why? Part of the issue is the chemicals that are created when you cook meat at high temperatures. Another part is that red meats contain high levels of “heme iron” (the type of iron found in blood and muscle), which promotes the growth of cancerous tumors.

McTiernan acknowledged science doesn’t have all the answers when it comes to figuring out the mechanisms that directly link colorectal cancer with red and processed meat. But “very high heat seems to release carcinogens,” she said. “It’s better to have a diet of more plants and lower fats and meats. And really limit your intake of highly processed meat, most of which are made of red meat.”

Load up on plants (and fiber)

Many of us have been raised to think every meal should consist of a slab of meat, some kind of bread or starch and maybe a veggie. But McTiernan advised we move away from these "Mad Men"-style meals of steak, baked potato and miniscule salad and, instead, cancer-proof our plates.

“Meat should take up less than one-quarter of the plate,” she said. “Vegetables should be half the plate and then some kind of whole grain on the other one quarter.”

Plants, not meat, should dominate our meals, said McTiernan. This serves us in a few different ways. If we eat mainly vegetables, we’re taking in fewer calories so we’re better able to control our weight. And plants — and their dietary fiber — fend off cancer by providing us with a slew of anti-cancer agents, by reducing intestinal transit time and by increasing fecal bulk.

Non-starchy vegetables are the best sources of fiber (think broccoli, Brussels sprouts, lettuce, cabbage and artichokes). Peas, lentils, beans and nuts also pack quite the fiber punch as do fruits like berries, apples and pears, especially if you eat the skin. Fruits are also a rich source of vitamin C, another nutrient that may protect against developing colorectal cancer.

“Overall, a lot of fiber is helpful,” McTiernan said. “We don’t know if it’s because it gets the food out of the body faster or if it’s something about the fiber itself — maybe it helps with absorption of vitamins. It’s just better to have a diet of more plants. You don’t have to be a vegetarian; just have an overall pattern of plant-based meals.”

Limit your booze

Yes, we love a glass of wine after a long day. But when it comes to alcohol and cancer, less is definitely more.

The new research points to a number of probable associations involving everything from toxic metabolites to oxidative stress to cellular penetration of carcinogens. But after sifting and sorting hundreds of studies, the bottom line is as clear as a shot of potato vodka: Consumption of alcohol is a “convincing cause” of colorectal cancer, especially if you drink more than 30 grams — or two drinks — a day.

McTiernan, who recently co-authored a paper on alcohol’s impact on breast cancer risk (yes, it’s a problem there, too), was sympathetic but straightforward about this finding.

“Really limit your use of alcohol,” she said.

Diane Mapes is a staff writer at Fred Hutchinson Cancer Research Center. She has written extensively about health issues for NBC News, TODAY, CNN, MSN, Seattle Magazine and other publications. A breast cancer survivor, she blogs at doublewhammied.com and tweets @double_whammied. Email her at dmapes@fredhutch.org.

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