Colorectal cancer is the third most common cancer world-wide and the second leading cause of cancer death. As reported in 2024 in the journal Critical Reviews in Food Science and Nutrition (June 24, 2024) colorectal cancer incidence is rising in younger people. This relates to the fact that colorectal cancer development, in most cases, involves an interplay between genetics and environmental factors (especially dietary factors). The review provides convincing evidence, that taken together, studies show that a diet that is high in red meat and alcohol is associated with an increased risk of colorectal cancer. A diet that is high in dietary fiber, calcium and yogurt is associated with a lower risk of colorectal cancer.

They also report that studies show that colorectal cancer patients have better survival outcomes after medical treatment if they follow a diet that is more plant-based, is low in refined and starchy carbohydrates, and includes fish (high in omega-3 fats), whole cereal fiber, vegetables, and wholegrains, but not fruit, and excludes alcohol. Whereas poorer survival outcomes are associated with a diet high in refined grains and sugar-sweetened beverages. (1)

Another study published in 2024 in the journal Gastroenterology suggests very strongly that a person’s diet largely determines the composition of the gut microflora (bacteria that live in the large intestine) and that high levels of certain gut bacteria are strongly associated with the development of colorectal cancer. In their analysis of the Health Professionals Follow-Up Study and the Nurses Health Study and the Nurses Health Study II, which comprised over 6,464,378 person-years, they found that individuals with high gut concentrations of three specific gut-bacteria were at much high risk (20-40 % higher risk) for colorectal cancer. The three gut bacteria include:

Fusobacterium nucleatum (F. nucleatum)
The pks strain of E. Coli
Enterotoxigenic Bacteroides Fragalis (ETBF)

Examining stool samples from thousands of individuals the most striking finding from these studies was that individuals with the highest intake of processed foods and the lowest intake of fiber-rich foods had higher stool levels of these three colorectal cancer-linked bacteria and these individuals experienced a roughly 25-40% increased risk of developing colorectal cancer, compared to individuals who consumed few processed foods and regularly consumed high fiber foods. As the researchers concluded, “A dietary pattern with a low consumption of processed foods may help prevent colorectal cancer through modulation of the gut microbiome.”

From my perspective, the evidence has been mounting for many years that a high animal fat, high refined carbohydrate diet is strongly linked to colorectal cancer development, whereas a diet with less animal fat (with the exception of fish) and higher in fiber-rich plant-based foods is associated with a lower risk of colorectal cancer, in general.  But we learn from recent studies that highly processed foods, including bacon, luncheon and deli meats may be even more dangerous than high animal fat foods alone, as these foods tend to encourage the proliferation within the gut of dangerous bacteria that appear to be involved in colorectal cancer development. (2) Adding to this evidence, an April 2024 report from the Fred Hutch Cancer Center cited evidence that a high meat diet increases colorectal cancer risk by 30% and a diet high in processed meat increased colorectal cancer risk by 40%. For individuals with certain genetic traits the consumption of red meat and/or processed meat increases colorectal cancer even further.  They also point out that obesity and regular alcohol consumption are strongly correlated with increased risk of colorectal, even in people under 60 years of age. (3)

My advice is to begin getting colorectal cancer screening by age 45 or 50, in most cases, and to remain at or near your ideal body weight, avoid red meat and processed meat as much as possible, don’t drink alcohol or use it judiciously, avoid sugar-sweetened beverages, and ingest fiber-rich vegetables, grains and legumes (beans and peas) on a daily basis. I also think that low-fat, sugar-free yogurt is a good way to obtain friendly gut bacteria as well as calcium, which are both associated with lower colorectal cancer risk in many studies. One last comment is that if you are using a protein shake to support your muscle and lean mass, make sure the protein shake contains less than 1 gm of fat, is low in sugar and is enriched with gut-healthy dietary fiber.

I have provided the key references for this information in the text below.

References:

Fretwell A et al. Still too little evidence: the role of diet in colorectal cancer survivorship – a systematic review. Critical Reviews in Food and Science Nutrition. June 11, 2024. https://www.tandfonline.com/doi/full/10.1080/10408398.2024.2360068#abstract

Wang K et al. An empirical dietary pattern associated with gut microbial features in relation to colorectal cancer risk. Gastroenterology. August 6, 2024. An Empirical Dietary Pattern Associated with the Gut Microbial Features in Relation to Colorectal Cancer Risk – Gastroenterology (gastrojournal.org)

Colorectal Cancer Risk and Red and Processed Meat. Hutch News Stories. April 23, 2024. https://www.fredhutch.org/en/news/center-news/2024/04/colorectal-cancer-risk-boosted-by-red-processed-meat-genetics.html

Eat Smart, Live Well, Look Great,
Dr. Meschino