Late Eating Linked to Higher Risk for Colorectal Cancer

3 min read

May 23, 2024 – Experts have long cautioned against eating late at night, especially a large meal loaded with fats or sugars. Now there’s another reason to listen to their advice: Eating within 3 hours of bedtime at least 4 days a week could increase chances for developing colorectal cancer. 

Researchers in a new study questioned 664 people getting a colonoscopy to screen for cancer, and 42% said they were late eaters. This group was more 46% more likely than non-late eaters to have an adenoma – a small noncancerous lesion – found during colonoscopy.

An adenoma is not cancer, but an estimated 5% to 10% of them become cancerous over time. The risk varies based on their location in your GI tract and their size. Doctors search for, measure, and count them during a colonoscopy. 

“A lot of other studies are about what we eat but not when we eat,” said Edena Khoshaba, lead investigator and a medical student at Rush University Medical College in Chicago. “The common advice includes not eating red meat, eating more fruits and vegetables – which is great, of course – but we wanted to see if the timing affects us at all."

Khoshaba and colleagues found it did. Late eaters were 5.5 times more likely to have three or more tubular adenomas compared to non-late eaters, even after adjusting for what people were eating. Tubular adenomas are the most common type of polyp found in the colon. 

So what’s the possible connection between late eating and the risk for colorectal cancer? 

Resetting Your Internal Clock

Eating close to bedtime could be about throwing off your body’s internal clock or “circadian rhythm.” In this case, it’s not the central circadian center located in the brain – the one that releases melatonin to make you sleepy at night. Instead, late eating could mess with your “peripheral circadian rhythm” or how other parts of your body know to adjust things when day turns to night. 

Part of this peripheral system is found in our gastrointestinal tract. For example, if you’re eating late at night, your brain thinks it is nighttime and your gut thinks it is daytime, Khoshaba said in an interview at this year's Digestive Disease Week conference in Washington, DC. 

This is an interesting study, said Amy Bragagnini, spokesperson for The Academy of Nutrition and Dietetics, when asked to comment on the research. “It is true that eating later at night can disrupt your circadian rhythm.”

“In addition, many of my patients have told me that when they do eat later at night, they don’t always make the healthiest food choices,” Bragagnini said. “Their late-night food choices are generally higher in added sugar and fat. This may cause them to consume far more calories than their body needs.” So eating late at night can also lead to unwanted weight gain. 

An unanswered question is if late eating is connected in any way at all to increasing rates of colorectal cancer seen in younger patients

This was an observational study, which is not as strong as research that randomly assigns people to a late or non-late eating group and compares their outcomes over time. Another possible limitation, Khoshaba said, is that people were asked to recall their diets over 24 hours, which may not always be accurate. 

Are You Keeping Your Stomach Bacteria Awake?

Some of the tiny organisms in your gut have their own internal clocks that follow a daily rhythm, and what you eat determines how many different kinds of these organisms are active, Bragagnini said. 

“So if your late-night eating consists of foods high in sugar and fat, you may be negatively impacting your microbiome.”

The next step for Khoshaba and colleagues is a study looking at the peripheral circadian rhythm, changes in the gut microbiome, and the risk for developing metabolic syndrome.