Focus on cancer-cure over prevention may be costing lives, warn leading oncologists and nutritionists

31 Jul 2019 --- Nutrition-based cancer prevention may be a crucial avenue that is not being engaged with yet, say leading oncologists and nutritionists. Translating research on nutrition and diet into cancer recommendations and policies, as well as improving mechanisms to share data across continents, could galvanize proper nutrition-based prevention. This is according to an international collaborative led by Ludwig Cancer Research and Cancer Research UK, which aims to identify key areas central to uncovering the complex relationship between nutrition and cancer.

Almost 40 percent of cancers are preventable, according to Linda Bauld, Cancer Research UK’s Prevention Expert, who spoke exclusively to NutritionInsight.

“There are potentially 760,000 additional cases of cancer that will happen over the next 20 years if we don’t reduce overweight and obesity, which are conditions primarily caused by diet. Even if we reduce that by just one percent every year, we could still prevent a lot of cancer,” she states.

Although it is unclear how cancer is caused, or its precise interaction with diet, physical activity, and being overweight, there is good evidence that carrying too much fat is directly linked to 13 different kinds of cancer. “However, when we look at dietary factors separately from being overweight and obesity, we don’t actually know conclusively what the best diet for protecting against cancer is,” Bauld adds. 

Bauld estimates that nutrition could be hugely important, especially in preventing a second cancer occurring. Despite a lack of strong clinical evidence linking diet, nutrition and cancer, Bauld estimates that it could be hugely important, especially in preventing a second cancer occurring. 

“One in two of us born after the year 1960 in high-income countries will develop cancer in our lifetime. We have some emerging evidence that nutrition might really help those people prevent a second cancer, but we don’t know exactly what this is, so we need more research.”

The collaborative says that advancing research on core areas using a holistic, cross-disciplinary approach could increase the progress that is urgently needed to prevent cancer and improve public health globally. Their main observations and conclusions are reported in a Forum article published online today in BMC Medicine.

“While data clearly show that obesity is a major risk factor for cancer, we still have a lot to learn about how diet, physical activity and other metabolic factors impact cancer development,” says Bob Strausberg, Deputy Scientific Director of the Ludwig Institute for Cancer Research. 

Methodological challenges in engaging with prevention
Traditionally, there have been several methodological challenges with studying the impact of nutrition on cancer risk, development and treatment. 

Environmental exposures in early life – including diet – can influence cancer risk in the future. However, the impact of these factors has been difficult to track from childhood to adulthood. Also, our understanding of the fundamental biological mechanisms behind these long-term effects is limited.

“The complexity of the metabolic factors modulated by diet and physical activity may be a contributing factor to the lack of support for several prominent food and cancer hypotheses in large prospective studies,” wrote section leads Walter Willett, Professor of Epidemiology and Nutrition at the Harvard T.H. Chan School of Public Health, and Elio Riboli, Chair in Cancer Epidemiology and Prevention at Imperial College London.

What research improvements might help?
Bauld suggests researchers make better use of the large population studies with big cohorts, as the first challenge in this space is measurement.Nutrition-based cancer prevention may be a crucial avenue that is not being engaged with yet.

“It’s very easy to measure how much someone smokes or how much alcohol they drink. To try to understand people’s diets, we often get them to keep a daily diary, but it’s difficult to understand diet over the long-term with that type of approach. We have huge datasets across many countries, and we’re not using them adequately. If we could merge our big population-level datasets together, that would be great,” she explains.

A second area to focus on would be longer-term studies that follow children into adulthood, while examining the role of diet. “For example, we know that if a child is overweight or obese, they are five times more likely to be overweight or obese as an adult, and we know that causes cancer. We don’t know if childhood overweight and obesity is a factor in that, or if it's just the fact that they’re carrying too much extra fat when they’re older,” she says.

However, another barrier comes to the fore when investigating cancer-prevention over cure. Bauld cites “politics” as the bottom line as to why there is not enough funding in this arena.

“Politicians want to fund things that will help people in the next couple of years because they want to get re-elected. That is where research funding tends to go – essentially cures and not prevention,” she explains. 

The benefits of preventions are not going to be seen for possibly decades, so more funders need to be convinced to take that long-term view, she concludes.

By Laxmi Haigh