As published in the journal Nature, restricting intake of amino acids found in red meat and eggs was found to enhance cancer treatment in mice to slow tumour growth; restricting intake of methionine was focused on which is important to one carbon metabolism that helps cancer cells to grow.
Restriction of methionine is associated with anti-aging and weight loss, its importance to cancerous cells suggests that it may also be a way to enhance cancer treatments.
“These are very strong effects, and they are effects that are as strong as we would see with drugs that work,” said lead researcher associate professor Jason Locasale of Duke University’s School of Medicine. “What this study is showing is that there are many situations where a drug by itself doesn’t work, but if you combine the drug with the diet, it works, or the radiation therapy doesn’t work well, but if you combine… with the diet, it works well.”
Methionine restriction was first tested in healthy mice to confirm its effects on metabolism, then studies moved to testing on mice with soft tissue sarcomas and colorectal cancer. Low dose of chemotherapy on its own had no effect but when combined with methionine restriction led to “marked inhibition of tumour growth” on colorectal cancer. Combining radiation therapy with methionine restriction had similar results on soft tissue sarcoma.
“You’re starving the cancer cells of certain nutrients, at a very basic level,” explained Locasale. “This is certainly not a be-all, end-all to cancer, this is not some panacea. What it’s showing is that there are very interesting interactions between the food we eat, how it changes metabolism… and then how those changes in cellular metabolism might have an effect on tumour growth.”
“Before drawing any conclusions about the potential for dietary restriction as an approach to treating cancer, human studies are needed,” said Paul Pharoah, a professor of Cancer Epidemiology at the University of Cambridge.
Further study involving restricting methionine intake in 6 healthy humans was found to have similar effects to those seen in the mice; findings suggest that diet may have a similar effect on certain tumours in humans, although larger studies are needed to draw definitive conclusions.
Tom Sanders, professor emeritus of nutrition and dietetics at King’s College London, warned that “there is no evidence from this study to suggest following a vegan diet with help patients with cancer.”
Nutrition research often struggles for funding as it proposes treatments that are not easily monetizable, according to Locasale, who notes that this work adds to a growing body of evidence suggesting that diet plays an important role in cancer treatment.
A chemotherapy drug was shown to be more effective when combined with a diet that was low in sugar while being high in protein and fat; and other cancers appear to be better battled when in combination with low sugar diets.
Locasale hopes that in the future doctors will be able to advise cancer patients to follow specific diets to assist their treatment,
“we may not be there yet, but the goal is to eventually get there.”
