A new research article published in Nature, “LLGL2 rescues nutrient stress by promoting leucine uptake in ER+ breast cancer,” showed a correlation between diets high in the amino acid leucin and some breast cancers. Researchers at the Beth Israel Deaconess Medical Center (BIDMC) Cancer Center have uncovered a link between leucine and tamoxifen resistance in estrogen-receptor positive (ER+) breast cancer, which hint that patients may benefit from reducing how much animal protein they eat. Studies headed by Senthil K. Muthuswamy, PhD, and colleagues, in cultured cells and in mice, indicated that reducing leucine levels suppresses ER+ breast cancer cell proliferation, and showed that a key leucine carrier that is responsible for importing the amino acid into cells acts to regulate response to tamoxifen.

“Our findings in the lab demonstrate that decreasing leucine levels suppresses proliferation of tumor cells, whereas increasing leucine enhances it,” commented Muthuswamy, who is director of the cell biology program and deputy director of translational research in the Cancer Research Institute at BIDMC. “Furthermore, the findings open up the possibility that a low-leucine diet could be beneficial for patients with ER+ breast cancer … Because animal proteins have a higher amount of leucine compared to plant proteins, this study begins to identify a diet intervention strategy to help patients with ER+ breast cancers.”

Though this is something that we’ve been saying for years, it certainly is nice to have some research to ‘back-up’ our claims!

Foods highest in Leucine: (foods to avoid)

  • Cheese (Parmesan, Romano, Swiss, Gouda, and hard goat cheeses are highest)
  • Soybeans (all sources)
  • Beef
  • Chicken
  • Pork
  • Seeds and Nuts (Sunflower, Chis, Pistachio, Sesame, Almonds, Cashews, Peanuts, and Brazil nuts)
  • Fish
  • Seafood