How Does Diet Affect Sleep? Findings from a New Study | humanOS.me

As a researcher who studies the relationship between sleep and eating, I’m often asked how diet affects sleep. Should I avoid carbs at night? When should I eat proteins and fats? What should I eat to get great sleep? While there is a growing body of evidence that sleep time and quality impact eating behaviors, there is less research on how the food choices we make today affect the quality of sleep we get tonight. So, how does diet affect sleep?

Recently, research by Marie-Pierre St-Onge and colleagues, published in the Journal of Clinical Sleep Medicine (1), evaluated whether sleep is modified in response to changes in dietary intake across the day. The study kept healthy participants in an inpatient unit, so there was a high degree of control to record what the participants ate and how they slept. During the first 4 days, the researchers gave the participants a controlled diet and monitored their sleep in response to what they ate. On day fifth day, however, the participants were allowed to choose their own food, and on that night, sleep changed: it took longer for the participants to fall asleep, they had less deep sleep and more arousals across the night.

So, what dietary factors predicted these changes? The three most notable factors were the consumption of dietary carbohydrate, fiber, and saturated fat. What did what? More fiber intake on the eat-anything-you-want day associated with positive sleep changes, including less shallow sleep and more deep sleep. Saturated fat and sugars, on the other hand, didn’t fare well. Increases in saturated fat, for instance, associated with less deep sleep, while more sugar and non-fiber carbohydrates associated with more arousals during slumber. While the study at hand doesn’t answer all questions on the subject, it does give us insight into how elements of diet might affect aspects of sleep quality.

Interpreting this information further, what we now see are signs of a potential feedback loop: certain changes in sleep duration and quality – including reductions in deep sleep and REM sleep – associate with increases in hunger and energy intake from fat and energy-dense forms of carbohydrates, like sugars (2). Eating more saturated fat and sugar within your day may then, in turn, negatively affect aspects of sleep quality at night. It’s just one other reason to maintain a healthy diet high in fiber, lower in certain fats, and low in sugar: a healthy diet may help you get better sleep, and better sleep may help you maintain a healthier diet.