A Low Methionine Diet: New Data for Cancer Therapy Favors Plant Foods
Amino acids are the building blocks of all proteins in the body. A subcategory of amino acids contain sulfur and includes methionine (Met) and cysteine, which not only make up proteins but also play many roles in metabolism and health. Researchers have been interested in dietary sulfur amino acid restriction since the 1990s, when studies began to show health benefits in animals fed Met-restricted diets. In one early study involving rats, 80 percent Met restriction increased average and maximum lifespans by between 42 and 44 percent. Pictured below is another study in yeast demonstrating extended lifespan with Met restricted diets.
Scientists have long known that animals on calorie-restricted diets live longer and healthier, but they’ve been searching for ways bring about the improvements without asking people to eat less. In a review of studies, sulfur amino acid restriction consistently demonstrated a range of beneficial effects including enhanced lifespan — without calorie restriction. The analysis found that Met restriction has been associated with delayed aging and longer lifespans in human cells, yeast, and animals including fruit flies and rodents. Animals fed sulfur amino acid-restricted diets also had health improvements including reductions insulin sensitivity; and more efficient fuel-burning. But can a Met restricted diet be of value in cancer therapies now or in the future?
This week researchers at Duke University showed that dietary restriction of Met influences cancer outcome, through controlled and reproducible changes to one-carbon metabolism. This pathway metabolizes Met and is the target of a variety of cancer interventions that involve chemotherapy and radiation. Met restriction produced therapeutic responses in mouse models of chemotherapy-resistant colorectal cancer and soft-tissue sarcoma. Measurements of metabolism revealed that the therapeutic mechanisms of Met restricted diets operated via one-carbon metabolism that affects redox and nucleotide metabolism — and thus interact with the anti-metabolite or radiation intervention used to treat tumors in human clinical medicine. The researchers also studied a controlled and tolerated feeding study in humans of a Met restricted diet. Met restriction resulted in effects on systemic metabolism that were similar to those obtained in mice (although there was no assessment of tumor growth in these healthy volunteers). These findings provide evidence that a targeted dietary manipulation can specifically affect tumor-cell metabolism to mediate broad aspects of cancer outcome.
Should you adopt a low Met diet? When you study the list of foods that are high in methionine below you will see that the dietary sources that are high in methionine are almost exclusively animal based foods that have many reasons to limit or eliminate. Maybe better than the MED (Mediterranean diet) is the low Met Diet?