Along with eating right and exercise, people should consider adding another healthy habit to their list: turning out the lights.

That’s according to a new study reported in the Cell Press journal Current Biology, which shows many negative health consequences for mice kept under conditions of constant light for a period of months.

“Our study shows that the environmental light-dark cycle is important for health,” said Johanna Meijer of Leiden University Medical Center in the Netherlands. “We showed that the absence of environmental rhythms leads to severe disruption of a wide variety of health parameters.”

Those parameters included pro-inflammatory activation of the immune system, muscle loss, and early signs of osteoporosis.

“The good news is that we subsequently showed that these negative effects on health are reversible when the environmental light-dark cycle is restore,” said Meijer.

This has wide implications for anyone working in the wellness industry, and suggests that more care should be taken in considering the amount of light exposure people get.

The bottom line, according to the researchers, is "light exposure matters."