Study breakdown · medRxiv preprint, 2026
Can More Fibre Help You Sleep Better?
What you eat during the day may subtly shape how you sleep that night—but the latest evidence is a reason to improve your plate, not buy a sleep supplement.
You can get the evening routine right—dim the lights, put away the phone, keep a regular bedtime—and still overlook something that happened hours earlier: what you ate.
A new analysis suggests that the fibre density of the day’s food may be associated with small changes in sleep architecture that same night. People had slightly more deep and rapid eye movement (REM) sleep, slightly less light sleep, and a lower sleeping heart rate after higher-fibre days.
The signal is interesting. It is not yet proof that adding fibre will improve anyone’s sleep.
What the study found
In a February 2026 medRxiv preprint, researchers analysed 4,793 person-nights from 3,598 generally healthy adults in Israel. Participants logged their food in a mobile app, while a home sleep device recorded sleep stages, duration, efficiency, awakenings, and heart rate.
The researchers compared days above and below the study population’s median for 25 dietary measures. They used statistical weighting to account for previous-day diet and sleep, age, sex, body mass index, physical activity, smoking, alcohol, caffeine, medical history, and daily mood and stress.
After correction for multiple comparisons, higher fibre density was associated with:
Participants averaged 6.3 hours of sleep, so those percentages translate to roughly two extra minutes of deep sleep and three extra minutes of REM sleep. Light sleep decreased by 1.35 percentage points. Total sleep time did not meaningfully change with fibre density.
This was not simply a comparison of people who habitually eat very different diets. The design used one day’s food to predict the following night’s sleep and adjusted for the preceding day’s measurements. That strengthens the analysis, but it does not turn it into a randomised feeding trial.
Fibre density, not a magic dose
The study measured fibre in grams per 1,000 calories. In other words, a higher-fibre day was one in which more of the day’s energy came packaged with fibre-rich food.
The higher group averaged about 15.7 g of fibre per 1,000 kcal, compared with about 9.1 g in the lower group. Those numbers describe the groups in this study; they are not a tested sleep prescription or a threshold everyone should chase.
The wider food pattern mattered too. Eating a greater variety of plant foods and a higher proportion of whole plant foods was associated with a slightly lower sleeping heart rate. Meanwhile, the percentage of energy coming from protein, carbohydrate, or fat showed no robust association with the sleep outcomes after statistical correction.
That is a useful reminder that food quality can tell us something a macro split cannot. Beans and a soft drink both contribute carbohydrate, for example, but only one brings fibre and a complex food matrix with it.
Why the result needs restraint
The paper is a preprint, meaning it has not yet completed peer review. It also has the usual limits of observational nutrition research:
- Food intake was self-reported and may have been under-logged or recorded inaccurately.
- Sleep stages were classified by a validated home device using proprietary algorithms, not a full laboratory polysomnogram.
- Statistical adjustment cannot remove every difference between higher- and lower-fibre days. An unusual day, stress, exercise, alcohol, or another unmeasured factor could still contribute.
- The mostly middle-aged, generally healthy Israeli cohort may not represent other ages, populations, shift workers, or people with sleep disorders.
- The study examined next-night associations, not what happens after months or years of eating more fibre.
The result is also small. An extra few minutes in a sleep stage is not something most people will feel the next morning, and we do not know whether the difference improves health.
Still, it is not an isolated observation. A small 2016 inpatient study of 26 adults found that greater fibre intake on a self-selected eating day predicted more slow-wave sleep, while more saturated fat predicted less. That was a secondary analysis with one day of self-selected food, so it supports the pattern without settling causality.
The practical move: add whole plants
You do not need a special bedtime food. Build more fibre into meals across the day:
- Add beans, lentils, or chickpeas to soups, curries, salads, and pasta sauces.
- Choose oats, wholegrain bread, brown rice, barley, or wholewheat pasta more often.
- Keep berries, pears, apples, vegetables, nuts, and seeds in regular rotation.
- Swap a low-fibre snack for fruit, vegetable sticks with hummus, or a small handful of unsalted nuts.
The NHS recommends getting fibre from varied food sources and increasing it through ordinary foods such as whole grains, pulses, vegetables, fruit, nuts, and seeds. If your current intake is low, increase it gradually and drink enough fluid; sudden large changes can be uncomfortable. People who have been advised to restrict fibre for a digestive condition should follow their clinician’s guidance.
The bottom line
Higher-fibre days were associated with a little more deep and REM sleep and a slightly lower sleeping heart rate in a large real-world dataset. The differences were measured in minutes, the paper has not yet been peer reviewed, and the design cannot prove that fibre caused them.
Two extra minutes of deep sleep is not a reason to buy a fibre supplement. Consistently falling short on fibre, however, is a good reason to put more beans, whole grains, fruit, vegetables, nuts, and seeds on the plate. Better sleep would be a welcome bonus to the better-established benefits of that dietary pattern.