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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.

Related Episode:

• M&M 237: Circadian Biology: Genetics, Behavior, Metabolism, Light, Oxygen & Melatonin | Joseph Takahashi

*Not medical advice.

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