Coffee may have an unexpected link to breast cancer survival – here's what researchers found

Every day, it seems there’s another study revealing a new reason why coffee might be good for us. In the past few years alone, researchers have linked regular coffee consumption with a lower risk of frailty in older age, increased longevity, a reduced risk of liver problems and type 2 diabetes, and even slower brain ageing.

Long gone are the days when coffee was simply demonised as a cortisol-spiking vice. These days, a growing body of research suggests that a daily brew may have a place in a healthy diet – with recent research even linking up to five cups a day with heart health benefits.

And last month, a study published in the British Journal of Nutrition added another potential benefit to coffee’s health CV, linking regular consumption with a lower risk of breast cancer mortality and recurrence.

But if you’re not a fan of coffee, don’t worry. The study also identified two key groups of polyphenols – natural compounds found in plants – that could help explain these associations. And coffee is far from the only way to get them.

This was an observational study, meaning the researchers observed participants' diets and health outcomes rather than asking them to follow a specific intervention.

Previous research has associated higher intakes of bioactive compounds such as polyphenols with better outcomes among people with breast cancer. For this study, researchers from the Federal University of Santa Catarina in Brazil wanted to investigate whether specific classes of polyphenols were associated with breast cancer survival and recurrence.

They followed 95 women diagnosed with breast cancer for an average of 11.5 years. During the study, researchers assessed participants' polyphenol intake using questionnaires about the foods and drinks they regularly consumed.

The researchers found that higher intakes of polyphenols – particularly two classes known as phenolic acids and lignans – were associated with better outcomes.

Higher phenolic acid intake was most strongly associated with a lower risk of breast cancer recurrence and death from any cause, while higher overall polyphenol intake was associated with improved breast cancer survival.

Perhaps most interestingly, coffee was the main source of total polyphenols, phenolic acids and lignans in the participants' diets – making it an important contributor to their intake of these compounds.

However, it's important to remember that this was a small observational study. It can identify associations, but it cannot prove that coffee or polyphenols directly caused the better outcomes observed.

So, the study linked higher polyphenol intake with better breast cancer outcomes – but how might these compounds be involved?

While this study wasn't designed to establish the biological mechanisms behind the association, existing research offers some clues.

In short, polyphenols can act as antioxidants in the body, helping protect cells from oxidative damage and influencing inflammatory processes.

Phenolic acids and lignans have different properties, too. Some phenolic acids are readily absorbed in the intestine, while lignans are classified as phytoestrogens – plant compounds that can interact with oestrogen pathways. Research has investigated whether this could play a role in hormone-sensitive cancers.

Coffee's rich polyphenol content is also thought to contribute to some of the other potential health benefits associated with drinking it.

If you already drink coffee, these findings add to a growing body of research exploring its potential health benefits. But they aren't a reason to start drinking large amounts of coffee specifically to reduce your risk of breast cancer or its recurrence.

And if you don't like coffee, struggle with caffeine or simply want to cut down, there are plenty of other ways to consume polyphenols.

Eating a wide variety of plant foods can also help increase your fibre intake – itself associated with a whole host of health benefits – while providing a range of vitamins and minerals.

You don't necessarily need to target individual polyphenols, either, as many plant foods contain several different types.

Foods containing phenolic acids, lignans and other polyphenols include:

• Flaxseeds
• Sesame seeds
• Oats
• Buckwheat
• Walnuts
• Berries
• Soybeans

The takeaway? Coffee may be one useful source of polyphenols, but it's the wider pattern of your diet – rather than any single drink – that matters most.