Humans, like other animals, become more sensitive to cold with age. Now, scientists from University of Utah Health report that delivering a single dose of a nutritional supplement called L-carnitine to older mice restores a youthful ability to adapt to the cold. After treatment, they tolerate chilly conditions that would ordinarily trigger hypothermia. As reported online in Cell Metabolism, the supplement works by boosting levels of a newly discovered fuel source for brown fat, or “good fat”.