Researchers are increasingly finding that diet plays an important role in cancer development and are even exploring what is considered a “paradigm shift”: acting on nutrition “not only to prevent cancer, but as a therapeutic intervention” say Marcos Malumes and Nabil Djouder, researchers at the National Cancer Research Centre (CNIO) and organisers of the international congress on diet and cancer being held this week at CNIO in collaboration with Fundación La Caixa.
It is not about curing cancer through diet, but about supplementing treatment with precise nutritional strategies. As Djouder and Malumes state, “it is very possible that new nutrition-based therapies will be incorporated into standard cancer treatments.”
One of the strategies that researchers are looking into intensely at the moment is intermittent fasting, which was discussed at the congress by Rafael de Cabo (National Institutes of Health, USA) and Valter Longo (Institute of Molecular Oncology, Italy; Longevity Institute, University of Southern California, USA).
“We have been studying strategies that mimic fasting to fight cancer for years, with good results; we are now moving to the phase where oncologists are beginning to consider its use in combination with standard therapies,” says Longo “The interesting thing is that it seems to work with very different cancers and in combination with different therapies. So it looks like a very promising approach.”
‘The Longevity Diet’
In his book The Longevity Diet, Longo advocates the use of intermittent fasting both in the prevention of disease and to supplement cancer therapies.
Research is already clarifying what happens in the cells during fasting, and why this may help stop tumours. “Tumour cells do not know how to stop their cycle, they are continuously functioning; healthy cells, on the other hand, if you cut off their energy supply, they automatically stop all division processes,” he explains. As chemotherapy is primarily aimed at cells that are proliferating, if given when the patient is fasting, its toxicity will mainly affect tumour cells, and the dose may even be increased.
Alejo Efeyan, head of CNIO's Cellular Metabolism and Signalling Group, also highlights the therapeutic potential of nutrition: “Diet, and the genes that trigger over-eating and obesity, are closely related to cancer. We can try to treat and prevent cancer through nutritional strategies, altering diet and the functions of the associated genes. But we still have much to learn to do it effectively.”
The observation of human populations with long lifespans and low rates of cancer; studies with animal models to understand what happens on a molecular scale; and highly controlled clinical trials are the kinds of studies that have demonstrated, over the years, the close relationship between diet and cancer.
How a Poor Diet can Contribute to Cancer
“The body puts a great deal of metabolic effort into processing nutrients and storing the derived products, from which we get energy,” explain Djouder and Malumes. “Altering this process or forcing it in the wrong direction for years and years causes stressful situations in cells that causes some of them to become pro-tumorous and, perhaps along with other factors, contribute to the development of a tumour.”
That is why, according to these researchers, “for most of the population, living habits such as nutrition generally play a greater role than genetic factors, at least in modern societies. It is clear today that nutritional habits underlie many of the most common types of tumours, especially gastrointestinal and hormone-dependent breast or prostate cancers.
One of the recommendations about which there is full consensus is that obesity negatively affects cancer. The researchers do not point to any one particular nutrient that is harmful, but generally to excessive consumption of any food group: “In modern societies, there are examples of excesses for all of them: carbohydrates – the most common excess – fats, and proteins,” say the organisers.
As for the best diet to prevent cancer, the recommendation is: plenty of fruits, vegetables, and legumes, and low levels of fats and red meats, processed foods, and alcohol.
What is not understood in depth is the reason for these facts. For example, red meat: “statistically, its consumption correlates with cancer; but the hard thing is knowing why exactly, whether it is related to amino acids, hormones, or parasites”.
Taking Care of Microbiome
Another area of greatest interest is microbiome, the population of microorganisms that literally populates our entire body. Yasmine Belkaid (National Institute of Allergy and Infectious Diseases, National Institute of Health, USA), a pioneer in his study, points to the role of microbiome in inflammation, and their influence on cancer through this phenomenon.
“Our diet influences the composition and diversity of intestinal microbiota, so-called intestinal flora, which can change with specific foods,” notes Djouder. “Alterations in the intestinal flora can cause general inflammation or the production of harmful metabolites, which impact on the development of many diseases, including cancer.”
But defining a "good diet" for healthy microbiota "is complicated", she adds. As a general recommendation, “a varied diet can be a basic medicine to maintain the proper functioning of intestinal flora”.
Nutritional Habits & Cancer
The congress also addresses the problem at the population level. Marina Pollan (National Centre for Epidemiology, ISCIII), Nuria Malats (CNIO), and Aurora Pérez Cornago (University of Oxford, UK) will discuss studies that correlate life habits, including nutrition, and cancer. Malats, an expert on pancreatic cancer, focuses “on the complex relationship between diabetes and obesity and pancreatic cancer, and how genetics and microbiome can explain part of this association”.