Flu season is upon us once again, and with COVID still circulating, it’s more important than ever to do everything we can to boost immune health & stay healthy.

Optimizing your body’s immune defenses is key.

New research published July 2023 from the University of Pennsylvania is now showing that optimizing your circadian rhythm may also help boost your body’s immune defenses against viruses like influenza [the flu].



What is circadian rhythm?
Your biological “clock” – suprachiasmatic nucleus
What happens when circadian rhythms are disrupted?
Recent studies on circadian rhythm and immune health
How exactly does circadian rhythm impact immunity and recovery?
Tips to optimize your circadian rhythm to give your body an edge against the flu

8 minute read


What is Circadian Rhythm?

Circadian rhythm refers to your body’s internal body clock. The term “circadian” has its origin in Latin. It is derived from the Latin words “circa,” meaning “around” or “approximately,” and “diem,” meaning “day.” Therefore, “circadian” essentially translates to “around a day” or “approximately a day.”

The body’s biological clock is located in a small region in the brain called the suprachiasmatic nucleus (SCN). The SCN is located in the hypothalamus, which is a region at the base of the brain.

It regulates physical, mental and behavioral changes that follow a 24-hour cycle. It plays a major role in your body’s immune function and ability to fight off infection.


Suprachiasmatic nucleus

The suprachiasmatic nucleus (SCN) is a small region in the hypothalamus that serves as the master circadian pacemaker, regulating the body’s internal clock. It receives input from light-sensitive cells in the eyes, synchronizing circadian rhythms with the external day-night cycle.

The SCN generates circadian signals, influencing processes such as the sleep-wake cycle, hormone secretion, and body temperature. Disruptions to the SCN, caused by factors like irregular sleep patterns can lead to disturbances in circadian rhythms and impact overall health.


What happens when circadian rhythms are disrupted?

Disruption of circadian rhythms, whether through irregular sleep patterns or other factors, can have various adverse effects on both physical and mental health. Some of the consequences of circadian rhythm disruption include:


Immune System Dysfunction

The circadian system interacts with the immune system, and disruptions can lead to immune system dysfunction, increasing susceptibility to infections and inflammatory conditions.


Sleep Disturbances

The most immediate impact is often on the sleep-wake cycle. Disruptions can lead to difficulties falling asleep, staying asleep, or experiencing restorative sleep, resulting in insomnia or other sleep disorders.


Impaired Cognitive Function

Circadian rhythms play a role in cognitive performance, memory, and attention. Disruptions can lead to impaired cognitive function, difficulty concentrating, and decreased alertness.


Mood Disorders

Circadian rhythms influence the regulation of mood-related hormones. Disruptions may contribute to mood disorders such as depression and anxiety.


Metabolic Consequences

Circadian rhythms play a role in regulating metabolism. Disruptions can contribute to metabolic disorders, insulin resistance, and an increased risk of obesity.


Hormonal Imbalances

The circadian system influences the release of hormones, including cortisol, melatonin, and growth hormone. Disruptions can lead to hormonal imbalances, affecting various physiological processes.


Cardiovascular Health

Circadian rhythms influence blood pressure and heart rate. Disruptions may contribute to cardiovascular problems, including hypertension and an increased risk of cardiovascular disease.


Digestive Issues

Circadian rhythms influence digestive processes. Disruptions may contribute to gastrointestinal issues, including irritable bowel syndrome (IBS) and other digestive disorders.


Increased Risk of Chronic Diseases

Prolonged disruptions to circadian rhythms have been associated with an increased risk of chronic diseases, including certain cancers, diabetes, and neurodegenerative disorders.


Recent Studies on Circadian Rhythm and Immune Health:

Recent research published in the Journal of Clinical Investigation has found compelling evidence that disrupting your circadian rhythm can worsen lung infection outcomes and impair your body’s ability to repair and regenerate lung tissue after illness.

In one part of the study, researchers analyzed data from over 84,000 participants in the UK Biobank database. They found that those with poor circadian rhythms had a higher likelihood of hospitalization for respiratory infections like the flu. They also spent longer in the hospital and had a higher risk of death after being discharged.

Another key part of the study looked at mice infected with influenza virus at different times of day. Mice infected at dusk had much worse lung damage and poorer oxygen levels a month later compared to those infected at dawn. Genetically disrupting the circadian clocks in lung cells also led to impaired repair and regeneration after infection.


How exactly does circadian rhythm impact immunity and recovery?

The circadian rhythm profoundly influences immunity and recovery processes. It helps control when the immune system is active, making sure important parts like white blood cells and cytokines follow a daily pattern. This coordination makes the immune responses work better during the day.

Additionally, the circadian rhythm controls inflammation, ensuring a balanced and appropriately timed inflammatory response to infections. It influences the recruitment and activity of immune cells, contributing to an effective defense against threats.

The circadian system also plays a vital role in cellular repair, regeneration, and the overall recovery of tissues and organs after infection or injury.

And more specifically related to study data discussed previously in this article…

Studies have shown it controls the timing and levels of inflammation in the lungs. But this research found it also independently enhances processes of lung repair, proliferation, and regeneration through distinct circadian-controlled mechanisms in different lung cell types.


So how can you optimize your circadian rhythm to give your body an edge against the flu?

Here are some tips based on the research:

  • Establish a regular sleep-wake cycle by going to bed and waking up at consistent times every day, even on weekends. Sticking to a schedule helps keep your circadian rhythm strong.
  • Expose yourself to bright light in the mornings within 30 minutes of waking to help reset your body clock. Open the curtains as soon as you wake up.
  • Limit light exposure in the evenings, especially from artificial blue-light emitting screens like phones, tablets, and computers. Install computer software that filters out blue light in the evenings.
  • Exercise daily, but earlier in the day rather than late afternoon or evening. Morning exercise has been shown to boost immunity.
  • Avoid heavy meals close to bedtime, which can disrupt your body’s circadian signals.
  • Manage stress levels with relaxation techniques. Chronic stress has been linked to weakened circadian rhythms.
  • The study mentioned considering supplements but did not mention resveratrol (such as ResveraMost), but other studies have confirmed the use of resveratrol to assist entraining the circadian rhythm.



By following these circadian-optimizing lifestyle habits, you give your immune system a boost and optimize your body to repair and regenerate at its peak capacity just in case a viral infection strikes you during flu season. A strong, well-regulated circadian rhythm may be one of your best everyday defenses.