Scientists in Japan have found that a natural compound in blueberries and grapes may help muscle cells break down fat. The team from Shinshu University studied pterostilbene, a substance found in these fruits. In their laboratory, they tested this compound on mouse muscle cells and saw that it helped lower fat inside the cells, while still letting the cells grow normally.

The scientists wanted to understand how muscle fat could be reduced, since too much fat in muscles can happen as people get older, move less, or eat high-fat foods. This problem is called myosteatosis, and it can make it harder for muscles to use energy. The team discovered that pterostilbene worked by protecting a special protein in the cells. This protein, called PPARδ, helps control how the cells burn fat.

Because this test was only done in mouse cells in the lab, there is no proof that eating blueberries will burn fat in human muscles. More research on animals and humans is needed to show if pterostilbene works safely outside the laboratory.