Coffee drinkers have a much lower risk of cancerous tumours re-growing in the bowels, according to new research.

An observational study among 1,719 people in the Netherlands has found that patients with colorectal cancer who nurse at least two cups of joe a day are less likely to relapse in the future. Drinking a few cups a day also seemed to reduce their chances of an early death.

This was true for patients suffering from all but the latest stages of bowel cancer, which were excluded from the analysis.

Today, bowel cancer resurfaces after treatment in up to 30 percent of patients, which means that if the recent findings from the Netherlands can be verified in larger studies, coffee could one day be recognized as a life-changing medicine for some cancer patients.

Compared to colorectal cancer patients who drank fewer than two cups of coffee a day, those included in the study who drank at least five cups a day had a 32 percent lower chance of their disease returning in the next six years or so.

During that same time frame, there was also a noticeable link between how much coffee a patient drank and their risk of dying from any cause, according to an international team of researchers, led by scientists at Wageningen University in the Netherlands.

Three to five cups of coffee a day was associated with the greatest reduction in all-cause mortality – peaking at roughly 29 percent compared to those who drank less than two cups. But after more than five cups a day, that peak dropped off.

The results suggest that drinking as much coffee as possible doesn't improve a cancer patient's odds, and it could even have negative outcomes for other aspects of their health. It seems there's a sweet spot to aim for.

The study in the Netherlands is one of the first to consider how coffee drinking impacts relapse rates among bowel cancer patients, not just their survival rates.

The only other study to investigate this question found no association between drinking coffee and cancer recurrence. But it focused only on patients with stage III colon cancer, whereas the recent study in the Netherlands looked at bowel cancer stages I to III.

Unfortunately, specific causes of death could not be evaluated with the data at hand, so it's impossible to say if survival rates among coffee drinkers in the Netherlands are reducing the risk of dying from bowel cancer specifically, or if there's another protective effect at play.

Some studies have, for instance, linked coffee's potent antioxidant properties to improved cardiovascular outcomes. Other research suggests the drink could protect against some types of skin cancer, liver cancer, womb cancer, prostate cancer, or even oral cancer.

"The mechanisms that underlie the potential benefits of coffee consumption on [colorectal cancer] recurrence are yet to be fully elucidated," write epidemiologist Abisola Oyelere and colleagues.

Most research so far has been purely observational, but the link between coffee and longer life spans has been found in several other parts of the world.

A 2018 study in the US, for instance, found that colorectal patients who consumed more than four cups of coffee a day had a 30 percent lower risk of all-cause mortality compared those who drank no coffee at all.

The same study also found that consuming more than four cups of coffee a day reduces the risk of mortality by up to 54 percent among patients with any stage of colorectal cancer, including the most advanced cases.

"Our finding on all-cause mortality was similar… " write Oyelere and colleagues, "regardless of the potential differences in the coffee preparation and serving techniques."

A standard cup of coffee in the Netherlands, for instance, is about half the size of what you'd find in the US.

Perhaps coffee has this powerful therapeutic effect because it activates metabolic pathways that reduce oxidative stress. Or maybe it alters the microbiome of the gut to somehow prevent cancer proliferation in the intestines. Boosting the powers of the liver could be another way that coffee improves the body's fight against cancer.

Further investigation is needed.

"Although we cannot infer a cause-and-effect relationship in our observational study," the authors of the Netherlands study conclude, "our findings could inform future intervention studies and provide evidence to develop guidelines for [colorectal cancer] patients."

The study was published in the International Journal of Cancer.