Four foods that could reduce the risk of colorectal cancer

Eating a Mediterranean-style diet, which is rich in legumes, nuts, fruits and vegetables, can reduce the risk of colorectal cancer. Photo / 123RF
As a gastroenterologist, Trisha Pasricha, MD advises her patients to make small changes – one at a time, and once every month – to create new, healthier habits.
Question: I’ve been worried by the reports of colorectal cancer rising among younger people. What can I do to lower my risk?
Pastricha: Although we don’t have control over many aspects of why we develop cancer – including our genetics, our environment and our early childhood exposures – there are a few areas where our own decisions can have a big impact.
I advise many of my patients to start by changing their diet. Eating a Mediterranean-style diet, which is rich in legumes, nuts, fruits and vegetables, can reduce the risk of colorectal cancer by around 18%. But so many people have been raised on a typical Western diet of highly processed, low-fibre meals, and their palates are accustomed to it. I have only rarely met patients who can go from zero to 100 when it comes to a dietary change.
So what I recommend is making small healthy swaps until you create a new habit and lifestyle you’re actually comfortable with. Try making these changes one at a time, once a month:
1. Instead of sugar-sweetened beverages, try sparkling water. Many popular brands of sparkling water have no sugar. A 2021 analysis of the Nurses’ Health Study II, a landmark study of nearly 100,000 nurses in the United States whose lifestyle habits and other medical conditions were followed over decades, found that each serving of a sugar-sweetened beverage consumed per day during adolescence was associated with a 32% increased risk of early-onset colorectal cancer.
2. Instead of processed or red meat, try fish. Swap out the weeknight hot dogs or hamburgers for an easy salmon recipe that involves minimal prep. Smoked meats or meats that are cured with nitrates or nitrites (think sausages, bacon and deli meats like bologna) should especially be avoided. A study of over 500,000 European adults found that 100 to 200 grams of fatty or lean fish consumed weekly reduced colorectal cancer risk by 7%.
3. Instead of refined grains, try whole grains. Many of us are eating some form of a grain, such as rice or bread, at multiple meals every week. Refined grains such as white rice and breads made from white flour are low in fibre and other minerals. The higher dietary fibre found in whole grains, such as brown rice, quinoa and farro, can reduce your risk of colorectal cancer. For example, one meta-analysis found that three servings daily of whole grains is associated with a 17% colorectal cancer risk reduction.
4. Instead of boozy cocktails, try ones with non-alcoholic liquor. There is no amount of alcohol that does not raise your risk of cancer. So if decreasing your cancer risk is really the goal, I’m telling you to eliminate – not limit – your alcohol intake. Fortunately, non-alcoholic beverages are increasingly mainstream in ways that didn’t exist in the past. If you crave something festive or fun to unwind, you’ve got endless options.
My patients often struggle with the advice to cut alcohol. This is partially because we’ve created a culture that has normalised – often glamorised – light to moderate drinking. Especially since the pandemic, the amount of drinking that we might consider “normal” has shifted in the wrong direction – and we saw a deluge of health consequences as a result. It’s time to reset our framework.
But we’re fighting against old dogma that says wine is “good” for you. While past studies found there may be a small protective effect against cardiovascular disease with light alcohol consumption, a major 2023 meta-analysis debunked this entire idea, and no study has ever shown that these people also have a reduced risk of cancer. Because even drinking as infrequently as less than one standard drink per day raises the risk of cancer, researchers from the World Health Organisation now advise there is no “safe amount of alcohol consumption.”
Excess fat promotes a state of chronic inflammation in our bodies that raises the risk of colorectal cancer: While body mass index (BMI) is not a perfect measure, a large study from 2022 published in Gastroenterology found that, compared with people with a BMI of less than 25, those with a BMI of 30 or higher at age 20 had 2.5 times the risk of developing early-onset colorectal cancer.
If obesity is something you’ve been struggling with, and especially if you have a family history of colorectal cancer, it’s worth discussing all the options on the table with your physician. In recent years, scientists have found that GLP-1 agonists reduce the risk of multiple obesity-related cancers, including colorectal cancer, and bariatric surgery, similarly, decreases the risk of obesity-associated cancer and mortality among adults with obesity by 32%.
What’s especially worth noting is that in a study of over 1 million patients published last year in JAMA Oncology, researchers found that GLP-1 agonists reduced the risk of colorectal cancer among patients with Type 2 diabetes, regardless of weight or presence of obesity. We’re still learning about the many ways GLP-1 agonists impact our health, but they appear to improve our colorectal cancer risk through multiple mechanisms, some of which may not be related to weight loss alone.
Four important signs and symptoms of early-onset colorectal cancer, that is, colorectal cancer diagnosed before the age of 50, are rectal bleeding, iron deficiency anaemia, abdominal pain and diarrhoea. While these symptoms can be due to many other reasons that may have no cause for alarm, if you experience them, it’s important that you communicate promptly with a physician. In a 2023 study published in the Journal of the National Cancer Institute, people with three or more of these symptoms had a more than sixfold increased likelihood of being diagnosed with early-onset colorectal cancer. Of these, about half of patients experienced the first sign or symptom within three months of their diagnosis.