Clearing brain fog: The importance of circadian rhythms

Brain fog describes an inability to think or focus. It also presents with poor mood and lack of motivation. Often it comes paired with other conditions such as:

  • Multiple Sclerosis
  • POTS
  • Thyroid disorders
  • Chronic fatigue syndrome
  • Alzheimer’s disease
  • Aging.

The area of the brain dedicated to motivation, emotion, learning and memory is the hippocampus. During Alzheimer’s disease, the hippocampus is one of the initial areas of the brain to become damaged. And this leads to the disorientation and shot-term memory loss early in the disease.

Based on the symptomology behind brain fog, it seems obvious that it involves the hippocampus. But for proper function, the hippocampus requires a functioning circadian system. And importantly, it seems to be a potential relay station for circadian behaviors.

brain fog circadian

Circadian rhythms and brain fog

When we look at what circadian rhythms do, it’s clear why the hippocampus is important. First of all, it’s role in motivation helps motivate us to find food. And it’s role in spatial memory helps us remember where we found food. That way, our likelihood of finding it again increases.

Furthermore, factors that promote a strong circadian rhythm promote new nerve formation in the hippocampus. Certainly Exercise and fasting. Probably the microbiome as well.

However, many think that syncing circadian rhythms simply involves tinkering with light exposure. Maybe some of the more deeply read on the subject understand the importance of time-restricted eating.

But clearing brain fog requires much more than these 2 aspects of circadian rhythms. Everyone should start there and continue those habits for at least 4 week. However, don’t be surprised if it requires more effort.

Entraining the hippocompaus

Many people erroneously believe that light entrains circadian rhythms in the brain. While the master clock is located in the suprachiasmatic nucleus(SCN) of the brain, the rest of the areas in the brain are peripheral clocks. As a consequence, they’re not always primarily entrained by light.

The feeding/fasting cycle entrains the hippocampus. Mice without access to feeding cues perform poorer on memory tasks. Furthermore, mice subjected to social jet lag perform worse, specifically on tasks dependent on the hypothalamus. Both time-restricted eating and calorie restriction provide these needed feeding cues.

Normally, hormones within the body signal environmental cues. For the food entrainable oscillator, insulin and insulin-like growth factor are the hormonal signals. Thus, if you are insulin resistant, you don’t have access to the food entrainable oscillator.

Therefore, correcting insulin resistance is key. Other outputs of the food entrainable oscillator including physical activity, good sleep, and other hormonal outputs are also required. At least for optimizing circadian rhythms and cognitive performance.

Redox balance is another important signal for entraining the hippocampus. The circadian rhythm of redox balance regulates the excitability of neurons in the SCN and the hippocampus. Factors regulating this include inflammation and antioxidant status. A recent study showed inflammation decreases alertness, affecting cognitive performance.

Physical activity, good sleep, and a healthy gut really move the needle on inflammation. So addressing these provide additive effects.

Stable circadian rhythms and brain fog in humans

A recent study showed that stable circadian rhythms increase cognitive performance in humans. The results were bolstered by functional MRI showing greater activity in the left hippocampus.

The authors attribute part of this effect to a better cortisol rhythm. Another important factor is that stable rhythms in behavior drive stronger cellular rhythms. Thus, nerves work better and repair optimal. A quote from the study:

“ These findings are the first to demonstrate that more consistent CARs are directly related to functioning of the hippocampus and that in turn is associated with successful memory performance in older individuals. This builds upon previous work illustrating that CARs are related to cognition…

These findings in healthy older adults support the hypothesis that the consistency of the CAR(Circadian activity rhythm) is linked to cognitive performance”

This backs up anecdotal evidence of a similar effect by comprehensively addressing circadian rhythms.

“I feel very motivated, clear headed, and focused. I used to experience insomnia 1-2 nights a week for no rhyme or reason. That hasn’t happened in a few weeks. My body temperature is consistently up, which is nice going into winter!”

This individual was already doing the light exposure and time-restricted eating. So adding in the other factors increased her clarity dramatically. Fortunately, she didn’t have other underlying issues such as insulin resistance or dysbiosis so it only took 4 weeks.


Brain fog can really mess with your brain. It affects mental performance, motivation, and messes with your mood. Many factors contribute to brain fog, and chief among these is circadian rhythms.

The hippocampus is the area of the brain that regulates learning, memory, motivation, and mood. It’s undoubtedly involved in brain fog, and heavily regulated by circadian rhythms. To begin people with brain fog should invest in their circadian rhythms by optimizing light exposure and time-restricted eating.

Identifying and addressing insulin resistance and disturbances in the gut are also both important. In order to synchronize the hippocampus, proper insulin signaling is a must. Factors within the gut that drive problems include:

  • Inflammation(Via inhibiting butyrate uptake)
  • Leaky gut(By increasing inflammation)
  • Poor digestion/motility(By causing microbial dysbiosis)
  • Microbial dysbiosis(by altering butyrate uptake)

All of these factors are interrelated and heavily dependent on stable circadian rhythms. Getting light during the day, blocking blue light at night, and time-restricted eating are a great place to get the ball rolling. Fufther tweaks help optimize hippocampal function, and thus, cognitive performance.


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