A high level of HDL, the good kind of cholesterol, protects your heart and your brain. You’ve heard plenty about how to get that level up—exercise, drink red wine, eat HDL-boosting foods such as nuts and avocados.

Now two studies by researchers at University of Helsinki have uncovered another way to boost HDL—getting enough sleep. In fact, a little less than one week of skimping on sleep triggered a worrisome trend.

First study: Fourteen volunteers had their sleep restricted to only four hours a night for five days, while seven other volunteers were allowed to sleep normally. Compared to the well-rested volunteers, the sleep-deprived ones had a significant drop in the activity of genes that regulate cholesterol.

The researchers confirmed their results in a second study: They used data from 2,739 participants who filled out questionnaires about their sleep habits. Just like the sleep-deprived volunteers in the first study, those who reported that they regularly didn’t get enough sleep (less than seven hours) had less expression of cholesterol-regulating genes—and their HDL levels were lower than those who reported that they got sufficient sleep.

So keep up your heart-healthy lifestyle—exercise, red wine, a cardio- and brain-protective diet. But make sure to also get to bed at a reasonable hour. For help with that, read Bottom Line’s Guide to Better Sleep…No Sleeping Pills Needed.