High-glycemic-index carbohydrate meals shorten sleep onset.
Level 2 - randomized trial
Randomized crossover clinical trial in humans
PubMed 17284739 · doi:10.1093/ajcn/85.2.426
What was done
Twelve healthy men (aged 18–35 years) completed a randomized crossover trial evaluating the effects of meal glycemic index (GI) and timing on sleep. Following a familiarization night, participants underwent 3 test nights spaced 1 week apart in random order. They consumed standardized isocaloric meals (3212 kJ; 90.4% carbohydrate, 8% protein, 1.6% fat) consisting of either high-GI Jasmine rice (GI = 109) or low-GI Mahatma rice (GI = 50). Three conditions were compared: high-GI meal 4 hours before bedtime, low-GI meal 4 hours before bedtime, and high-GI meal 1 hour before bedtime. Sleep onset latency and other sleep parameters were assessed.
What was found
A high-GI meal consumed 4 hours before bedtime significantly reduced mean (±SD) sleep onset latency compared with a low-GI meal consumed 4 hours before bedtime (9.0 ± 6.2 min vs. 17.5 ± 6.2 min; P = 0.009). The high-GI meal consumed 4 hours before bedtime also produced a significantly shorter sleep onset latency than the same high-GI meal consumed 1 hour before bedtime (9.0 ± 6.2 min vs. 14.6 ± 9.9 min; P = 0.01). No effects on other sleep variables were observed.
Why it matters
The study shows that manipulating dietary carbohydrate glycemic index and meal timing can meaningfully reduce sleep onset latency in healthy individuals.
Limits
The sample size was very small (n = 12) and restricted strictly to healthy young men, limiting generalizability to women, older populations, and individuals with clinical sleep disturbance. The trial only tested acute single-meal interventions rather than long-term dietary patterns.
Cited by
- supports Scientific research shows that dietary intake of starches improves sleep.