Running on myelin
Marathon runners’ myelin levels in the brain temporarily dwindled in the days after a race. The finding suggests that this fatty tissue that insulates nerve cells may be an energy source for the athletes, Meghan Rosen reported in “Brain tissue may help fuel marathoners” (SN: 11/18/23, p. 16).
Reader Julian Young wondered whether myelin levels could also drop in people on a restrictive diet such as the low-carb keto diet or in people who experience low blood sugar levels for long periods.
It’s unknown whether ketogenic diets affect myelin levels. Such diets “generally don’t cause clinically relevant hypoglycemia,” so enough glucose remains in the body to fuel brain cells, says neurologist Russell Swerdlow of the University of Kansas School of Medicine in Kansas City. However, extreme calorie restriction, such as that experienced by people with anorexia nervosa, can decrease myelin levels in the brain, says Carlos Matute, a neurobiologist at the Achucarro Basque Center for Neuroscience and the University of the Basque Country in Leioa, Spain.
Reader Kimberly Barden asked whether the marathoners’ myelin loss might be connected to the phenomenon known as runner’s high.
Runner’s high has no obvious relationship with myelin loss, Matute says. The phenomenon “is associated with the release of certain neurotransmitters and endorphins in the brain. This feature activates reward brain circuits that generate a state of euphoria and well-being,” he says.
Beyond reproduction
Chimpanzees in Uganda are the first known example of nonhuman primates in the wild to experience menopause and live well past their reproductive years. The finding raises questions about how the hormonal changes evolved, Bruce Bower reported in “Menopause affects wild chimps too” (SN: 11/18/23, p. 8).
In humans, the ovaries typically stop releasing eggs during menopause. Reader Gerry Beard wanted to know whether the same is true…
Read the full article here