Seafood at breakfast stood out in a study of nearly 6,000 adults

By Dr. Priyom Bose, Ph.D.Reviewed by Lauren HardakerSep 1 2026

Researchers tracked when nearly 6,000 Japanese adults consumed seafood and omega-3 fatty acids to investigate whether the time of day we eat may be connected to the timing of our internal body clock.

Study: Association between the Timing of Seafood, EPA, DHA Consumption and Sleep Pattern: A Cross-Sectional Study. Image Credit: Sasazawa / Shutterstock

A recent study in the Journal of Nutritional Science and Vitaminology investigated the association between the timing of seafood intake and sleep patterns, including chronotype and social jetlag, using dietary and sleep data from a large sample of adults.

The Role of Omega-3 Fatty Acids in Sleep Regulation

Human sleep patterns are shaped by individual chronotypes, such as a morning or evening preference, and can be disrupted by social jetlag, the misalignment between sleep schedules on workdays and days off. Seafood, especially varieties rich in omega-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), has been linked to beneficial effects on sleep.

EPA and DHA are long-chain fatty acids known to influence neural function and sleep-related processes. Evidence from animal studies indicates that these polyunsaturated fatty acids can influence the entrainment of peripheral tissue clocks, suggesting that the timing of their intake could potentially be relevant to circadian regulation, although direct evidence in humans remains limited.

While the timing of nutrient consumption may play an important role in regulating biological processes related to the circadian rhythm and sleep-wake cycle, most human research has focused on total daily intake rather than when these nutrients are consumed. This leaves an important gap in understanding whether the timing of omega-3 intake is associated with sleep patterns and chronotype alignment. Exploring this relationship could help inform future dietary research aimed at supporting sleep health.

Exploring How Seafood Intake Timing Relates to Sleep Patterns

To assess how the timing of seafood (EPA and DHA) intake relates to sleep patterns, the study analyzed real-world data from 5,975 Japanese adults aged 18 to 75. The Japanese cohort included 64.9% women.

Dietary data were collected using Asken, a mobile health and food-logging application that enabled participants to log the content and meal occasion of foods and snacks. This approach allowed the researchers to estimate average consumption of seafood, EPA, and DHA across four meal categories: breakfast, lunch, dinner, and snacks. The study did not record the exact clock time at which foods were consumed.

Sleep characteristics were assessed using metrics based on the Munich ChronoType Questionnaire (MCTQ), a validated instrument for evaluating sleep patterns. Chronotype was determined by calculating the midpoint of sleep on free days and adjusting for sleep debt accrued on workdays to position each participant along the morningness-eveningness spectrum.

Social jetlag, a measure of misalignment between biological and social clocks, was quantified as the difference in sleep timing between workdays and free days. To examine the relationships between the timing of nutrient intake and sleep outcomes, the researchers employed Generalized Estimating Equations (GEE). Intake measures were generally divided into higher- and lower-intake groups using the median rather than being analyzed in quartiles.

Uncovering an Association Between Omega-3 Intake Patterns and Sleep Timing

The analysis demonstrated that total daily intake and the meal occasion at which seafood, EPA, and DHA were consumed were differentially associated with chronotype and social jetlag. Individuals with higher total daily intake exhibited a stronger tendency toward a morning chronotype and generally experienced less social jetlag.

Individuals with higher breakfast intake of seafood, EPA, or DHA had an adjusted sleep midpoint approximately 19 to 21 minutes earlier than those with lower breakfast intake, indicating a shift toward morningness. Additionally, higher breakfast intake was associated with approximately 5 to 6 minutes less social jetlag.

Meal occasion showed distinct associations: breakfast consumption of seafood and omega-3 fatty acids showed the strongest association with earlier sleep phases and less social jetlag, while lunch intake showed a smaller association. Dinner intake was not significantly associated with chronotype, although higher seafood intake at dinner was associated with slightly less social jetlag. In contrast, higher EPA and DHA intake from snacks was associated with a later chronotype and greater social jetlag. The authors cautioned that this may reflect broader snacking patterns among people with later chronotypes rather than an adverse effect of EPA or DHA itself.

These results suggest a potential mechanism whereby consuming long-chain omega-3 fatty acids earlier in the day may be associated with circadian regulation, potentially involving peripheral tissue clocks and other sleep-related pathways. However, these mechanisms are based largely on animal and prior experimental evidence and remain speculative in humans. As this was an observational cross-sectional study, the findings establish correlation rather than causation.

The direction of the relationship also remains uncertain. Earlier seafood intake may influence sleep timing, but people with a morning chronotype may be more likely to eat seafood at breakfast or lunch. Dietary intake was self-reported, and exact meal timing, meal regularity, and caffeine intake were not available for adjustment. The participants were also users of a dietary tracking application, which may limit the generalizability of the findings to the general population.

Conclusions

The current study highlights that both the quantity and timing of seafood, EPA, and DHA intake are significantly associated with sleep patterns and circadian alignment in Japanese adults. Consuming these nutrients earlier in the day, particularly at breakfast, was most strongly associated with a morning chronotype and lower levels of social jetlag, whereas dinner intake showed little association with chronotype, and EPA and DHA intake from snacks was associated with later sleep timing and greater social jetlag. These results suggest that not only the amount but also the timing of omega-3 fatty acid consumption may be related to sleep timing and alignment between workday and free-day sleep schedules.

However, as this research is cross-sectional, it demonstrates correlation rather than causation, and further studies are needed to determine whether intentional changes in the timing of omega-3 intake can directly improve sleep health. The researchers also noted that two of the authors were employees of Nissui Corporation and that the study received financial support from Nissui, along with partial support from the JST-FOREST Program.