A new study published in Nature Health has found that what people eat during the day may shape how well they sleep that same night, with fibre intake standing out as one of the strongest dietary factors linked to more restorative sleep.
Researchers examined 4,793 person-nights of real-world dietary logs and wearable sleep recordings, using a lagged-variable design that controlled for the previous day’s diet and sleep baseline. They reported that higher fibre density was associated with more deep sleep, more REM sleep, less light sleep and a lower mean nocturnal heart rate.
What the researchers found
According to the study, greater fibre consumption was linked with +0.59 percentage points deep sleep, +0.76 percentage points REM sleep, -1.35 percentage points light sleep and -1.14 beats per minute mean nocturnal heart rate. The authors also reported that greater plant diversity and higher whole-plant food intake were associated with lower nocturnal heart rate.
Meal timing also appeared to matter. Heavier evening meals, defined as the percentage of total daily energy consumed in the six hours before bedtime, were associated with 7.7 minutes longer total sleep time but a 0.73 bpm higher nocturnal heart rate.
Why the findings matter for diet and sleep
The study adds to growing evidence that day-to-day dietary choices may influence sleep physiology beyond long-term diet patterns. For people looking to improve sleep quality, the findings suggest that fibre-rich foods, plant diversity and the timing of meals may all play a role.
The research does not prove that fibre directly causes better sleep, but it does strengthen the case for looking at diet and sleep together in future nutritional guidance and clinical research. The authors used an observational causal-inference framework, which helps test associations in free-living conditions but still cannot replace a controlled intervention.
For healthcare professionals and patients alike, the results are a reminder that nutrition advice is not only about weight or cardiometabolic health. It may also be relevant to daily recovery, sleep depth and overnight cardiovascular stress.
As the evidence base evolves, the practical message remains straightforward: a more fibre-rich, plant-diverse diet may offer benefits that extend into the night.
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