TYPING the words nutrition and cancer on Google, in half a second, more than 5 million results appear: an indicator – the speed and volume of rumors – of the interest that researchers and patients arouse in the relationship between diet and tumors. But it is also – perhaps – an indicator of how much there is still to be done in order to fully understand this relationship. And it is doing. A study, published in Nature by researchers at the Massachusetts Institute of Technology (MIT), evaluated what happens when laboratory mice, which had been transplanted subcutaneously with a human pancreatic tumor, are given a low-calorie diet or a ketogenic diet. Well: the results show that calorie restriction has a much greater effect on tumor growth than the ketogenic diet.
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Starve the cells
Sugars do not cause cancer, as is often heard, but it is true that cancer cells consume glucose at a much faster rate than healthy cells, which is why it has been hypothesized that both the ketogenic and calorie restriction diets. by reducing the amount of glucose available, they could both slow down cancer growth. The ketogenic diet consists, in fact, in a regime that drastically reduces carbohydrates (or sugars) while increasing the intake of proteins and especially fats.
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The researchers then analyzed tumor growth and nutrient concentration in mice with human tumors on a ketogenic diet (with a normal calorie level, but made up of 90% fat, 9% protein and protein). 1% carbohydrates) or a low-calorie one (40% calorie reduction). The result was that glucose levels decreased in both groups while, as expected, lipids were higher in the former. “We discovered – the authors report – that only calorie restriction inhibits the growth of transplanted tumors in mice, which suggests that other mechanisms are at play”.
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But what other mechanisms? According to Giulia Salvadori e long walter of the Institute of Molecular Oncology of Milan -Ifom, who always sign a comment on Nature, the slowdown observed in the low-calorie diet would be mediated by changes in the levels of available fat. “Glucose levels – they write – have been reported as essential for the survival and growth of many types of cancer”, but this study shows that “tumor growth can be slowed by lipid imbalance […], paving the way for further research evaluating the involvement of other metabolites in the survival of cancer cells ”.
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What do lipids have to do with it?
The explanation provided by the authors is as follows. Deficiency in fat would impair tumor growth because cells need lipids to build their membranes. Normally, when lipids are not available in the tissues, cancer cells make their own and to do so they use Stearoyl-CoA Desaturase (SCD), an enzyme that converts saturated fatty acids into unsaturated fatty acids. Both the low-calorie and ketogenic diets reduced the enzymatic activity of SCD, but the mice that followed the ketogenic diet had the fats available from the diet, while those subjected to calorie restriction did not.
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Now let’s be clear: this study doesn’t mean cancer patients should try one of these diets for treatment. But what has been discovered deserves further investigation to understand how much and how different diets could be combined with cancer treatments to help patients. Matthew Vander Heiden, director of MIT’s Koch Institute for Integrative Cancer Research, medical oncologist at the Dana-Farber Cancer Institute and senior author of the publication reports that his patients often ask questions about the potential benefits associated with nutrition. “Many of these questions – he added – concern low-calorie diets, which reduce the consumption of calories by 25 to 50 percent, or ketogenic diets. But we don’t have enough scientific evidence to give definitive advice. There is a lot of evidence that diet can influence cancer progression, but we are not talking about a therapy. And while the findings are interesting, more studies are needed, and individual patients should discuss the right dietary interventions with their doctor. Many of the advice or trends that are out there – Lien warned – are not necessarily always based on good science “.
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Men and mice
It must also be said that the results come from a mouse model in which pancreatic tumors are implanted under the skin of mice – recalls Paul Pharoah, professor of oncological epidemiology at the University of Cambridge – and that the results obtained on animal models, although intriguing as these are often not observed even in the human being. Consequently, the relevance of these findings for pancreatic cancers that develop and grow in the human pancreas is speculative. “
Beware of malnutrition
“Overall, this is an interesting study on tumor growth mechanisms, but (…) it did not actually examine how cancer develops within an organ or tissue,” commented Duane Mellor, dietician. and senior lecturer at Aston University, who warns, “Although a review of pancreatic cancer survivors has indeed been examined, the risk associated with a low-glycemic and calorie-restricted diet in people with cancer in terms of wasting and malnutrition probably outweighs any benefit “.