Diet and cancer advice: then and now

Back in the 90s, diet was a hot topic. Many thought it could have a big impact on our risk of cancer.

The thinking back then was that fruits and vegetables were the key to beating cancer. It was thought that the more vitamins and antioxidants you ate, the less likely you were to develop cancer.

But scientists back then mostly had theories rather than strong scientific evidence.

Hunting for an anti-cancer diet

Studying diet and cancer is tricky for many reasons.

Back in the early 90s, the main way scientists studied diet and cancer was by asking people with cancer what they had eaten over the years and compared this to people without cancer.

But many people struggle to remember what they had for lunch yesterday, let alone what they had over many years.

Plus, it’s possible people with cancer remember things differently to people without.

Enter huge studies like the European Prospective Investigation into Cancer and Nutrition (EPIC) and UK Biobank. These studies recruited millions of healthy people and asked them about their diet, other life factors like levels of physical activity, as well as taking blood samples.

They then followed the people for many years to see how their diet, life and health changed over time.

This means we can now more reliably compare the diets of people who had gone on to develop cancer to those who hadn’t, while also accounting for other factors like smoking.

Surprising findings

Thanks to large long-term studies on cancer, we have a much clearer idea on what to eat to reduce the risk of cancer.

And the results have been surprising and changed how we think about diet and cancer.

While there’s no doubt fruits and vegetables play a role in a healthy diet, there’s no strong evidence that these actively prevent cancer, or that eating more antioxidants will reduce your risk.

The role of fruit and vegetables and dietary patterns on weight management appears to be far more important. Decades of research have highlighted the importance of keeping a healthy weight on cancer risk, second only to not smoking.

So while there are some foods directly linked to cancer (like processed meat), cancer recommendations now emphasise that your overall diet is more important than these individually.

Emma Shields is a NZ Registered Dietitian. She was previously Health Information Manager at Cancer Research UK. This article was inspired by a previous blog post she wrote.