Circadian rhythms are a cycle of mental, physical and behavioural changes of most living things (humans, animal, plants and microbes), which follow a daily cycle. Sleep, digestion, hormonal release and body temperature are all influenced by circadian rhythms. When they are disrupted or abnormal, chronic health disorders can result. Sleep disorders, depression, seasonal affective disorder (SAD), bipolar disorder, obesity and depression have been associated with irregular circadian rhythms.

Circadian rhythms respond primarily to dark and light, such as the rhythm of night - sleep; day - awake

Circadian rhythms and Biological clocks

Biological clocks are the body’s inborn timing device and can be found in almost all tissue and organs. Made of specific protein molecules which interact in cells throughout the body, biological clocks produce circadian rhythms and regulate their timing.

The master clock coordinates all biological clocks in living things

All of the biological clocks in the body are coordinated and synchronized by a master clock located in the brain. The master clock receives direct input from the eyes. It is a structure made of a group of about 20,000 neurons (nerve cells), called the suprachiasmatic nucleus (SCN), located in the hypothalamus part of the brain.

Circadian rhythms mainly take their cue from daylight

Daylight can turn on or off the genes which control the molecular structure of biological clocks. Changing the light/dark cycle results in a speeding up, slowing down or resetting of biological clocks and circadian rhythms.

The central role of circadian rhythms is coordinating an organism’s life with an earth’s day

Circadian rhythms effect on the body

Circadian rhythms have an influence on:

• Sleep patterns
• Hormone release
• Digestion
• Body temperature

When biological clocks run fast or slow, they can disrupt or result in abnormal circadian rhythms and this is linked to chronic health conditions.

What affects the circadian rhythm

When circadian rhythm regulation is disturbed it can have a major effect on the health of the body resulting in disease and disorders. Mental health – such as depression, and physiological problems – cardiovascular disease, diabetes, obesity, metabolic syndrome and cancer can be associated with disturbances in the circadian rhythm.

The circadian rhythm is affected by:

Environmental factors –
seasons, night and day duration and light

Lifestyles factors – 
poor sleep, shift work, diet

Hereditary – 
mutations in circadian genes

Cosmic events – 
cosmic spin and magnetic waves

Aging

Getting older has an affects on circadian rhythms. As we age two nutrients important for regulation of circadian rhythms decline. NAD+ and Melatonin.

NAD+ (nicotinamide adenine dinucleotide)

Nicotinamide adenine dinucleotide is a cofactor that is central to metabolism and found in all living cells. It contributes to the regulation of circadian rhythms and sleep-wake cycles. B3 converts biochemically to NAD+, an essential biological molecule in our body that supports the functioning of our cells. NAD+ metabolism has a close relationship with the efficient functioning of the circadian clock.

As we age our NAD+ levels decline and this decline is associated with cellular aging and chronic disease.

Supplements with NAD+ contain precursors which are substances that convert to NAD+ once in the body. NAD+ not only supports circadian rhythm regulation, it also helps with cellular communication, plays an important role in maintaining healthy metabolic function and protects the brain from damage from oxidative stress.

Melatonin

Melatonin is a hormone secreted by the pineal gland located in the brain. It is one of the major signaling molecules used by the master biological clock. Its secretion is affected by age, light, environmental and physiological factors, and genetics. Aging affects melatonin levels, but lower melatonin secretion also speeds up aging, along with visceral adiposity (fat around the waist), cardiovascular function and tumor development.

Supporting the circadian rhythm

Magnesium plays a role getting the rhythm right.

Getting enough dietary magnesium is important in helping the body to adapt to the rhythm change of day - to - night. Magnesium levels are also associated with the rate of metabolism in cells – when magnesium levels in the body are low, the ability of cells to convert nutrients to energy is low.

The importance of getting a good night sleep

• Cognitive processing. Being attentive is vital for performance of all activity. This includes learning, working, leisure activities and social interactions. Cognitive processing and performance can be affected by dysfunction in the circadian rhythm and sleep deprivation. Our ability to concentrate improves during the day and is lowest during night and early morning.
  ​
• Jet lag. Travelling to and through different time zones can interrupt circadian rhythms. It may take a few days to reset the biological clock to the new time zone.
   
• Maintain a regular sleep/wake pattern. This allows the body to anticipate and prepare for awake times and sleep times. Go to bed at the same time every day, and rise at the same time everday of the week and avoid daytime napping.
   
• Be active during the day. Exercise and enjoyable activities reduce stress and strengthen circardan rhythms, promote daytime alertness and improve sleep. Avoid stimulating activities close to bed time.
   
• Spend time in natural light during the day and darken the environment at night

Eat in rhythm

Not only do circadian rhythms respond to light but also to feeding times, adjusting clocks to respond to regular cues.

Eating times help modulate circadian rhythms

When irregualr eating patterns occur, as happens with shift workers for example, circadian physiology is dysrupted and chronic health disorders can occur, such as type 2 diabetes. 

• Make breakfast and lunch your bigger meals - to respond to your more active time of day and eat less at the end of the day
• Eat at the same times every day
• Fast between meals
• Limit caffeine containing beverages
• Avoid spicy foods in the evening

​Note: Intermitted fasting is being studied for its effects on the body and its ability to reset the body clock. Fasting is a natural occurance in nature due to food not always being available. When fasting, metabolic changes occur allowing for the body to adapt and essentially reprogram a variety of cellular responses. Let's face it - we eat too much too often. 
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​Supplement

• Melatonin
• NAD+ (nicotinamide adenine dinucleotide)
• Magnesium

In conclusion

As we age and with certain diseases, the circadian system can become depleted and the production of melatonin decreases leading to disturbance in sleep and the health of the of the body. Getting enough day light, exercise during the day, healthy sleep patterns and supplementing with NAD+ and melatonin can support the rhythms of the body. 

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References

https://www.nigms.nih.gov/education/pages/factsheet_circadianrhythms.aspx

Circadian Rhythm, Lifestyle and Health: A Narrative Review https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6123576/

Temporal partitioning of cardiac metabolism by the cardiomyocyte circadian clock. https://www.ncbi.nlm.nih.gov/pubmed/27474266

Circadian Rhythms in Attention https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6430172/

The Functional and Clinical Significance of the 24-Hour Rhythm of Circulating Glucocorticoids https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5563520/

New perspectives on the role of melatonin in human sleep, circadian rhythms and their regulation

https://www.sleep.org/articles/4-tips-maximize-circadian-rhythm/

The Functional and Clinical Significance of the 24-Hour Rhythm of Circulating Glucocorticoids https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5563520/

Age-associated changes in oxidative stress and NAD+ metabolism in human tissue. https://www.ncbi.nlm.nih.gov/pubmed/22848760

The Circadian NAD+ Metabolism: Impact on Chromatin Remodeling and Aging  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5165141/

Intracellular magnesium and the rhythms of life https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5134708/

Aerobic exercise improves self-reported sleep and quality of life in older adults with insomnia https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2992829/

Yoga for improving sleep quality and quality of life for older adults. https://www.ncbi.nlm.nih.gov/pubmed/24755569

https://www.cell.com/cell/fulltext/S0092-8674(19)30166-7?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0092867419301667%3Fshowall%3Dtrue

The Big Breakfast Study: Chrono‐nutrition influence on energy expenditure and bodyweight https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5969247/

Timed high-fat diet resets circadian metabolism and prevents obesity The FASEB Journal article fj.12-208868. Published online May 25, 2012.

https://www.medicalnewstoday.com/articles/324207.php