What you eat during the day may do more than fuel your body—it could also influence how well you sleep that night.

A recent study published in Nature Health found that higher fiber intake was linked to a small but measurable increase in time spent in deep sleep, the most physically restorative sleep stage.1

The finding doesn’t demonstrate that fiber alone is a sleep fix, but it adds to a growing body of research suggesting that diet may play an important role in sleep.

Plant Foods and Fiber Associated With Sleep Quality

Previous research has linked diets rich in fiber and minimally processed foods with better sleep, the researchers noted. However, they said most studies haven’t objectively measured sleep stages or accounted for other differences that might influence both diet and sleep.

The new study aimed to do both. Nearly 3,600 predominantly healthy adults logged their meals in real time through a mobile app and wore devices capable of distinguishing among sleep stages. The participants, whose average age was 53, were split roughly evenly between men and women. Altogether, they contributed 4,793 days of dietary and sleep data—the equivalent of about 13 years.

The researchers then examined how day-to-day changes in diet related to sleep hours later, while accounting for what the person had eaten and how they had slept the previous day.

They found that eating a greater variety of plant foods was associated with a lower nighttime heart rate. Meal timing also appeared to matter: Higher-calorie evening meals were linked to more sleep but a higher heart rate, while earlier dinners were associated with shorter sleep but healthier regulation of heart rate.

One of the clearest associations involved fiber—although the differences were small. Eating more fiber relative to total calorie intake was associated with 0.59 percentage points more time spent in deep sleep and 0.76 percentage points more in REM sleep, which plays an important role in brain health and function.

Notably, 25 of the 32 dietary factors studied—including carbohydrates, protein, and fat—weren’t consistently linked to sleep.

Keep in mind, however, that the study doesn’t prove that eating more fiber and a variety of plant foods directly improves sleep. Although the study’s design helped limit the influence of other variables that could affect the results, it couldn’t rule them out entirely. Randomized trials are needed to determine whether dietary changes can actually improve sleep—and who might benefit the most.

Why Fiber May Be Linked to Sleep

Fiber’s link to sleep could be attributed to its effects on blood sugar, said Karman Meyer, RDN, LDN, a registered dietitian who specializes in sleep support.

“When you include fiber-rich foods at dinner or as part of a bedtime snack, you slow down glucose absorption, which can prevent middle-of-the-night blood sugar drops,” Meyer explained.

When those drops occur, the body doesn’t simply wait them out. Instead, a blood sugar drop triggers the release of adrenaline and cortisol as a survival response, which could result in an increased heart rate, night sweats, and hunger pangs that interrupt your sleep, Meyer said.

Fiber-rich foods may also influence sleep through the gut microbiome. When gut bacteria break down fiber, they produce short-chain fatty acids, which may help regulate nervous system processes involved in sleep.2

Should You Consume More Fiber For Better Sleep?

While you shouldn’t view fiber as a fix for poor sleep based on the study finding’s alone, experts said that eating more fiber may be a reasonable, low-risk step that could support better sleep.

The research doesn’t establish how much fiber you would need to consume to see a potential sleep benefit. However, current guidelines recommend that adults aim for about 25 to 38 grams per day, depending on age and sex.3

Vegetables, fruits, legumes, and whole grains are all good sources—and the study suggests that eating a variety of these foods may offer an added benefit for sleep.

Beyond its potential sleep benefits, there are plenty of other reasons to eat more high-fiber foods. Fiber promotes healthy digestion, feeds beneficial gut bacteria, helps you feel full between meals, and supports healthy blood sugar and cholesterol levels. That’s why it’s an important part of a balanced diet, regardless of its effect on sleep, said dietitian