There is truth to the anecdote that your locks can lose color when you’re stressed.

Researchers have found that in mice, stressful events damage the stem cells that are responsible for producing pigment in hair. These stem cells, found near the base of each hair follicle, differentiate to form more specialized cells called melanocytes, which generate the hues in hair and skin.

Stress makes the stem cells differentiate faster, exhausting their number and resulting in strands that are more likely to be transparent — gray.

The study led by Harvard stem cell biologist Ya-Chieh Hsu and published in Nature, also found that the sympathetic nervous system, which prepares the body to respond to threats, plays a big role in the graying process. The sympathetic nervous system helps mobilize many biological responses, including increasing the flow of blood to muscles and sharpening mental focus. But the researchers found that in some cases the same system of nerves permanently depleted the stem cell population in hair follicles. The findings provide the first scientific link between stress and hair graying, Hsu said.

Is whole milk better for kid’s weight?

The American Academy of Pediatrics recommends switching to skim or low-fat (1%) milk at age 2.

But Canadian researchers analyzing 14 prospective studies including 20,897 children calculated that compared with children who drank low-fat milk or skim milk, those who drank whole milk (3.25% fat) were at a 39% reduced risk for overweight or obesity, and the risk for obesity declined steadily as whole milk consumption increased. The analysis is in the American Journal of Clinical Nutrition.

The authors speculate that it may be that children who drink whole milk consume fewer calories from other food. Some studies suggest that milk fat has properties that make people feel full.

Reverse causality could also be at play: It’s possible that skinny children have parents who offer them whole milk to fatten them up.