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How seasonal changes in light and dietary unsaturated fats affect circadian rhythms in mammals.

Topics Discussed:

Evolutionary context of circadian rhythms: All organisms have adapted to Earth’s 24-hour day for survival, with internal clocks slightly offset and adjusted by environmental cues.
Molecular clock mechanism: Involves a feedback loop where proteins turn on/off genes, lasting ~24 hours, regulated by phosphorylation and degradation for timing precision.
Genetic variations in sleep: Families with mutations in clock genes like PER2 cause extreme morning lark behavior, altering protein stability and period length by hours.
Light entrainment: Morning light shortens human clocks (average 24.2 hours) to match 24-hour days; seasonal day length changes require gradual adjustments.
Food & metabolic links: Seasonal food scarcity/abundance affects clock via glucose and fatty acids competing for protein modifications, as shown in diabetic mouse models.
Role of unsaturated fats: Paper finds MUFA/PUFA ratios in diet alter phosphorylation of clock proteins, speeding or slowing adaptation to winter/summer light cycles in mice.
Modern environmental impacts: Artificial light extends “daytime” signals, while constant food access erases seasonal patterns, contributing to obesity and diabetes risks.
Jet lag & adaptations: Sudden time shifts mimic seasonal experiments; high-sugar/fat intake may phenocopy genetic effects to aid adjustment, though not recommended for health.

Practical Takeaways:

Expose yourself to morning natural light to help synchronize your internal clock and improve daily energy.
Consume main meals during daylight hours and avoid late-night eating to align with natural metabolic rhythms.
Limit evening screen time to reduce artificial blue light disrupting sleep onset.
Consider varying diet seasonally, favoring diverse, whole foods to mimic natural availability patterns for better health.

About the guest: Louis Ptacek, MD is a neurologist and professor at the University of California, San Francisco. He researches inherited neurological diseases and sleep traits, including genetic variations causing extreme early rising.

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