Restricted caloric diets can impact tumor growth, study finds

21 Oct 2021 --- A restricted caloric diet reduces the availability of fatty acids needed to develop tumors, thus decreasing cancerous growth. This is according to researchers from the Massachusetts Institute of Technology (MIT) who examined these effects on mice.

“There is a lot of evidence that diet can affect how fast your cancer progresses, but this is not a cure,” says Matthew Vander Heiden, senior study author and director of MIT’s Koch Institute for Integrative Cancer Research.

“While the findings are interesting, further study is needed, and individual patients should talk to their doctor about the right dietary interventions for their cancer.”

Not only does caloric restriction starve tumors of lipids, but it also impairs the process that allows them to adapt to it. That combination contributes to the inhibition of tumor growth, comments Evan Lien, lead study author and postdoctoral fellow at MIT Koch Institute for Integrative Cancer Research.

“The study provides some sense of the mechanisms of how these diets work, and that can lead to rational ideas on how we might mimic those situations for cancer therapy.”

Further studies are needed
Following the study, the researchers now plan to study how diets with various fat sources – including plant or animal-based fats with defined differences in saturated, monounsaturated and polyunsaturated fatty acid content – alter tumor fatty acid metabolism and the ratio of unsaturated to saturated fatty acids.

Although this study showed that calorie restriction has beneficial effects in mice, researchers do not recommend that cancer patients follow a calorie-restricted diet, which is challenging to maintain and can have harmful side effects.Researchers flag that the study does not necessarily apply to humans. 

However, they believe that cancer cells’ dependence on the availability of unsaturated fatty acids could be exploited to develop drugs that might help slow tumor growth.

The research was funded by multiple cancer institutions, including the Damon Runyon Cancer Research Foundation, the National Institutes of Health and the Lustgarten Foundation.

Slow tumor growth
Previous studies have suggested that a calorically restricted diet might slow tumor growth in some contexts. Such a diet has been shown to extend lifespan in mice and many other animal species.

A smaller number of studies exploring the effects of a ketogenic diet on cancer have produced inconclusive results.

In the MIT study, researchers analyzed tumor growth and nutrient concentration in mice with pancreatic tumors fed either a regular, ketogenic, or calorie-restricted diet.

In both the ketogenic and calorie-restricted mice, glucose levels went down. In the calorie-restricted mice, lipid levels also went down, but they went up in mice on the ketogenic diet.

Lipid shortages impair tumor growth because cancer cells need lipids to construct their cell membranes. Normally, when lipids aren’t available in tissue, cells can make their own.

The study examined the effects of a calorically restricted diet and a ketogenic diet in mice with pancreatic tumors.

Patients and dietary impact
Patients often ask about the potential benefits of various diets. Still, there is insufficient scientific evidence available to offer any definitive advice, details Vander Heiden.

Many of the dietary questions that patients focus on are either a calorie-restricted diet, which reduces calorie consumption by 25 to 50% or a ketogenic diet, which is low in carbohydrates and high in fat and protein.Lipid shortages impair tumor growth because cancer cells need lipids to construct their cell membranes.

Study limitations
The study has attracted attention from other experts, who flag various limitations. Gunter Kuhnle, professor of nutrition and food science at the University of Reading, details that the results do not support any particular dietary pattern in contrast to the press release.

“The only modest reduction in risk was observed for people consuming a higher amount of plant-based fat, but the study does not provide any information on the actual amount of fat consumed.”

“In summary, this is a well-conducted study, mainly in mice, that provides further information on potential mechanisms linking diet with disease, but it is not easily possible to translate these results into recommendations for the public,” adds Kuhnle.

It is essential to consider that the tumors were from cells added under mice’s skin and not cancers linked to and developed in the actual organs, comments Dr. Duane Mellor, registered dietitian and senior teaching fellow at Aston Medical School, Aston University.

“Although the research mentions pancreatic and lung cancer, these were the type of cell cancers that grew under the skin of mice,” he concludes.

By Nicole Kerr