White fish, vegetables and regularity: simple markers of good sleep

Quality sleep isn’t just about “going to bed early.” A new study in Nutrients of 785 Spanish women aged 18-64 found that the “healthier” the lifestyle and diet, the better the subjective sleep; while alcohol and a love of ultra-processed food are more often associated with daytime fatigue, slow sleep onset, and a “ragged” night. The work rewrites the usual advice: it’s not about a trendy “general” diet, but about specific habits – from vegetables and white fish to regular activity and attitudes towards one’s own health.

Background of the study

Sleep disturbances are one of the most common complaints in adult women: sleep is affected by hormonal fluctuations (cycle, pregnancy, menopause), stress, caring for loved ones, shift work and social factors. In Southern European countries, a cultural pattern of the day is added: late dinners, an active evening social life and a “shifted” chronotype in some of the population, which increases the risk of circadian inconsistency and “social jet lag”. As a result, a significant proportion of women experience subjectively poor sleep quality, prolonged latency to fall asleep, frequent night awakenings and daytime sleepiness.

In recent years, it has become clear that sleep is closely linked to diet and lifestyle - not just through calories, but through specific food groups and habits:

• Alcohol may put you to sleep faster, but it fragments sleep and worsens its architecture.
• Ultra-processed foods (UPF) are associated with metabolic inflammation, reflux, and glycemic variability, which increases night awakenings.
• Fish and seafood (source of omega-3, iodine, vitamin D) and vegetables/fruits (fiber, polyphenols) support an anti-inflammatory background and microbiota, which is associated with more stable sleep.
• Moderate-intensity physical activity improves the depth and efficiency of sleep, while late-night high-intensity exercise may delay sleep onset in sensitive individuals.
• Daily routine (wake-up/bedtime, lighting, screen time in the evening) are the key “invisible” sleep regulators.

The Spanish population is interesting for studying these relationships for two reasons. First, the Mediterranean dietary pattern is widespread here, which is potentially “friendly” to sleep; second, in recent years, UPF and alcohol consumption has increased in some of the population, which may pull sleep in the opposite direction. At the same time, in women, hormonal status and well-being factors (self-assessed health, stress level) often mediate the effect of nutrition and habits on sleep.

Methodologically, most studies rely on validated sleep quality questionnaires (e.g. PSQI) and dietary/behavioural habits questionnaires. Such designs allow for the assessment of patterns of associations in large samples, but do not prove causality and are vulnerable to self-reporting bias. Therefore, cross-sectional studies in specific groups (e.g. adult women in Spain) are important as a step towards hypotheses for interventions: which specific dietary elements (vegetables, white fish, UPF proportion) and habits (alcohol, activity, evening routine) are associated with better sleep components and what makes sense to test in randomized interventions with objective recording (actigraphy/polysomnography).

How the study is structured

• Design: cross-sectional (survey) study with validated PSQI (sleep quality index) and NutSo-HH (nutrition and daily habits) scales. Recruitment: February-May 2025.
• Participants: 785 women, without acute/chronic conditions that are known to disrupt sleep. Average age - working-age adults (18-64).
• Analytics: Descriptive statistics, correlations (Spearman), Gaussian Graphical Models and PCA (principal component analysis) to identify “patterns” of relationships between sleep habits and components.

Overall, more than half of the participants rated their sleep as good/very good, but over 30% regularly woke up at night. Against this background, factors that are more often associated with "bad" sleep stood out: more alcohol, less vegetables and white fish, less physical activity and a more "nocturnal" lifestyle (late nights out, shifted rhythm).

What did they find?

• Food and sleep: More vegetables and white fish - better overall PSQI score; ultra-processed food eaters were more likely to report poor subjective sleep and daytime dysfunction. (Examples: vegetables 3.57 vs. 3.05 for “poor sleep”; white fish 1.75 vs. 1.42; UPF intake was moderately correlated with worse sleep).
• Alcohol: "getting drunk" at least occasionally is a marker of slow sleep onset and more "broken" night; moderate positive associations with sleep latency.
• Physical activity: more activity - slightly better overall PSQI (weak negative correlation), but the strength of the association is small: the type, intensity and timing of exercise are more important than the bare "hours".
• Lifestyle: "night" mode was associated with long latency and sleep fragmentation; self-assessment of health is a protective factor (worse assessment of health - worse sleep).
• Surprisingly, caffeine/stimulants, late meals, and diet “label” (e.g., Mediterranean/vegetarian) did not show strong associations with sleep components in this sample. That is, the quality of specific foods and habits is more important than the overall “brand” of the diet.

The pattern from PCA (principal component analysis) makes sense: fruits, vegetables, and white fish gravitate toward the “good sleep” clusters (longer sleep, higher efficiency), while fast food, fried foods, and ultra-processed foods gravitate toward the “bad sleep” clusters (more awakenings, daytime dysfunction, sleep medications). This doesn’t prove causality, but it does highlight a “pattern” in the data.

What does this mean in practice?

• Focus on simple markers of diet quality: more vegetables, fruits, white fish; less ultra-processed and fried foods. This is associated with better PSQI sleep scores.
• Alcohol is a frequent "subversive" of sleep architecture: the paradox of "fell asleep faster - wake up more often" with the result of being exhausted. Reduce and remove from the evening.
• Move regularly, but optimize timing and intensity: late-night "hard" exercise can interfere with sleep in sensitive people; light-moderate activity often helps.
• Follow your routine: a routine pushed into the night and frequent evening outings overload the circadian mechanisms and increase sleep latency.
• Work with your self-perception of health: the effect can go both ways - you better assess your health → better sleep; you sleep better → higher resourcefulness and resistance to stress.

Important detail: The study did not find a strong link between diet labels (e.g., “I eat Mediterranean”) and sleep — but it did find links between individual food groups and habits. This is an argument in favor of personalization: changing specific elements, rather than chasing dietary ideology.

Limitations to keep in mind

• Survey design and self-reports → risk of systematic errors (memory, social desirability).
• There are no objective sleep measurements (actigraphy/polysomnography) and hormonal/psychological markers that could explain the variability in women at different periods of the cycle/life.
• Cross-sectional: associations ≠ causation. Longitudinal and interventional studies are needed.

What would be useful to check next?

• Pilot interventions: reduce UPF/alcohol, add fish/vegetables - and look at actigraphy, sleep latency and fragmentation.
• More precisely about training: type/intensity/timing vs. cycle phases and chronotype.
• Biomarkers: inflammation, omega-3 status, vitamin D, heart rate variability, and objective sleep assessment.

Conclusion

Among the Spanish women in this sample, “good sleep” was more often associated with vegetables, white fish, regular activity, and a good self-assessment of health, while “bad sleep” was associated with alcohol, ultra-processed food, and a nocturnal lifestyle. Instead of trying to catch up with the “perfect” diet, it’s worth tweaking specific habits.

Source: Marín Ferrandis AV, Broccolo A., Piredda M., Micheluzzi V., Sandri E. Nutritional and Lifestyle Behaviors and Their Influence on Sleep Quality Among Spanish Adult Women. Nutrients. 2025;17(13):2225. Published July 4, 2025. https://doi.org/10.3390/nu17132225