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Circadian Rhythm

Episodes

Posted on September 27th 2024 (8 months)

In this clip, Dr. Andrew Huberman discusses the benefits of morning sunlight for sleep, timing, alternatives, and managing light exposure to optimize health.

Posted on April 1st 2023 (about 2 years)

Dr. Rhonda Patrick answers audience questions on various health, nutrition, and science topics in this Q&A session.

Posted on December 3rd 2022 (over 2 years)

Dr. Rhonda Patrick answers audience questions on various health, nutrition, and science topics in this Q&A session.

Topic Pages

  • Breast milk and breastfeeding

    Breast milk is a complex, dynamic fluid containing nutritional and non-nutritional components that support infant development. Breastfeeding benefits both infants and mothers.

  • Depression

    Depression – a neuropsychiatric disorder affecting 322 million people worldwide – is characterized by negative mood and metabolic, hormonal, and immune disturbances.

  • Fasting

    Fasting – the voluntary abstinence from food and drink – is an ancient practice now widely appreciated for its beneficial effects on healthspan.

  • Melatonin

    Melatonin is a hormone involved in the sleep-wake cycle that might also have benefits for neurodegenerative diseases like Alzheimer's and dementia.

  • NAD+

    NAD+ is a cofactor that plays an essential role in metabolism, DNA repair, and immunity. Its depletion accelerates aging.

  • Sirtuins

    Sirtuins play a key role in healthspan and longevity by regulating a variety of metabolic processes implicated in aging.

  • Sleep Regularity

    Sleep regularity refers to the consistency of one's sleep schedule and is associated with a wide range of physical and mental health outcomes.

  • Time-restricted eating

    Time-restricted eating is a form of daily fasting wherein a person eats only during a limited time window, typically 8- to 12-hours.

News & Publications

  • Working night shifts may increase the risk of cancer by disrupting the production of melatonin, a hormone essential for DNA repair. This disruption can impair the body’s ability to repair oxidative DNA damage, potentially contributing to cancer development. A recent study found that melatonin supplementation could improve the repair of oxidative DNA damage in night shift workers.

    The researchers conducted a four-week randomized, placebo-controlled trial with 40 night shift workers, providing them a 3-milligram dose of melatonin before their daytime sleep periods. They collected urine samples during daytime sleep and nighttime work periods, measuring 8-hydroxy-2′-deoxyguanosine (8-OH-dG), a marker of DNA repair capacity.

    They found that melatonin supplementation nearly doubled 8-OH-dG excretion during daytime sleep, indicating improved DNA repair. However, they observed no difference in 8-OH-dG excretion during the night shift. Although the melatonin group experienced a slight decrease in wakefulness after falling asleep, the researchers found no differences in total sleep duration or sleepiness levels between the two groups.

    The findings from this small study suggest that melatonin supplementation enhances oxidative DNA repair in night shift workers, offering the potential for reducing cancer risk. More extensive studies may identify optimal dosages and the long-term effects of melatonin supplementation in this population. Learn about the pros and cons of melatonin supplementation in this clip featuring Dr. Satchin Panda.

  • Modern workplace changes driven by technology are transforming not only how we work but also how well we sleep. Longer hours spent at desks, increasing reliance on computers, and nontraditional work schedules may undermine sleep health. A recent study found that modern job designs are linked to distinct sleep challenges among full-time workers.

    Researchers analyzed data from nearly 1,300 adults in the Midlife in the United States study, collected at two points over a decade. They examined six sleep health dimensions, including duration, insomnia symptoms, and daytime tiredness. Then, they identified three sleep health profiles: good sleepers (who had few sleep issues), catch-up sleepers (who relied on naps and non-workday sleep to offset shorter workday sleep), and insomnia sleepers (who experienced short sleep, frequent insomnia symptoms, and daytime tiredness).

    They found that only about half of the participants were good sleepers. Participants with sedentary jobs were more likely to be classified as insomnia sleepers. At the same time, those with nontraditional schedules often exhibited a catch-up sleeper pattern characterized by irregular sleep and regular napping. Good sleepers were less likely to be in these roles, suggesting that workplace design powerfully shapes long-term sleep health.

    These findings suggest that job design has marked effects on sleep quality. Reducing sedentary time and stabilizing work schedules could help workers achieve healthier sleep patterns, ultimately improving well-being and overall health. Learn how shift work and other aspects of modern lifestyles influence sleep and health by altering circadian rhythms in this clip featuring Dr. Satchin Panda.

  • Artificial light exposure increases the risk for obesity among children. Light is the primary signal that entrains the body’s master clock to set its 24-hour circadian cycle. Consequently, the body is synchronized to external light-dark cycles. In recent decades, exposure to light from artificial sources (rather than natural ones) has increased, paralleling the global increases in obesity among adults. Findings from a 2016 study suggest that exposure to artificial light increases the risk for obesity among children.

    Global health experts estimate that more than 42 million children under the age of five years have obesity, roughly one-fourth of whom live in developing nations. Obesity increases a person’s risk for developing chronic diseases such as type 2 diabetes, heart disease, and some cancers. It also imposes considerable financial costs at the individual, healthcare system, and national level.

    The study involved 48 preschool-aged children receiving daycare services in Australia. The investigators measured the children’s baseline body mass index (BMI), sleep duration and timing, light exposure, and physical activity levels via clinical assessment, parent questionnaires, and light and activity trackers. They repeated these measures 12 months later.

    They found that at baseline, children who had longer early exposure to moderate intensity light (such as that from artificial sources) were more likely to have higher BMI, while children who had longer afternoon exposure to bright light (such as that from natural sources) tended to have lower BMI. At the second assessment, the investigators found that even after taking into account sleep duration and timing, BMI, and activity levels, children who had more total light exposure at baseline (due to having earlier exposure) gained more weight than their peers. Specifically, for every hour earlier that the children were exposed to light, they experienced a 0.6 unit increase in BMI. The investigators posited that although this was a small increase, it could be an indicator of a life-long trajectory toward weight gain.

    These findings suggest that greater light exposure, especially when it occurs early in the day from artificial light sources, contributes to weight gain in children. Interestingly, adults that receive early exposure to bright light typically sleep better – a key to maintaining a healthy weight. Learn more in this clip featuring Dr. Matthew Walker.

  • Circadian rhythms play critical roles in human health. Maintaining these rhythms can be challenging, especially for people who work night shifts or travel across multiple time zones. Findings from a new study suggest that prebiotics can help restore the body’s natural rhythms.

    Prebiotics are food components that support the maintenance of a healthy microbiota and create an environment that is conducive to its survival. Fructo-oligosaccharides, galacto-oligosaccharides, and trans-galacto-oligosaccharides are the most common prebiotics. Their fermentation by gut microbiota produces short-chain fatty acids, including lactic acid, butyric acid, and propionic acid. Many commonly consumed fruits and vegetables, such as apples, bananas, and legumes, contain prebiotics.

    The authors of the study fed rats either a prebiotic-enriched diet or a standard diet. After the rats had been on their respective diets for five weeks, the authors either flipped their light/dark schedules (roughly equivalent to flying across 12 time zones) or left them on a normal schedule once a week for eight weeks. They measured the animals' sleep, brain activity, core body temperature, and locomotor activity. They also collected fecal samples from the animals and identified the types and number of gut microbes present.

    The rats that ate the prebiotic-enriched diet resumed their normal sleep-wake cycles, core body temperature, and activity levels faster than the rats that ate the standard diet. The rats on the prebiotic diet also had greater abundance of several health-promoting microbes, including Ruminiclostridium 5, compared to those on the standard diet. Previous research indicates that Ruminiclostridium 5 is associated with improved sleep.

    These findings suggest that eating a diet rich in prebiotics can help restore normal circadian rhythms following disruption, such as would occur after working shifts or traveling. Learn more about the effects of shiftwork on human health in this episode featuring Dr. Satchin Panda.