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The circadian rhythm is often associated with sleep, eating, and physical activity patterns. However, it is involved in many other processes in the body, including digestion and cellular function. The body is controlled by diurnal oscillations, which is why some activities seem easier at certain times of the day. This influence can impact the best times to eat meals and take nutritional supplements or medication.

Many complementary medicine traditions, such as Ayurveda and Traditional Chinese Medicine, incorporate circadian rhythms in their treatments. Western medicine is starting to recognize the power of these rhythms to facilitate treatments and contribute to dysfunction when they are in disarray.

Circadian Rhythm: Power and Importance

Every process in the body, including regulatory mechanisms against oxidative stress, the composition of the microbiome, and intracellular signaling, has some type of oscillating pattern that fits within a daily 24-hour rhythm. The body upregulates certain components of metabolism and mechanisms required for functions during active hours and down-regulates them during rest periods.

Several circadian transcription factors control positive and negative feedback loops in the cells to determine the functions of key organs and systems, including the heart, lungs, immune system, and metabolism, as well as the intracellular processes, such as cellular respiration and DNA repair. This internal clock system regulates roughly one-third of the body’s entire gene activity. Each person’s genetic code regulates these systems and affects the body’s timing for peak performance, such as whether that person is an early bird or a night owl.

The central regulator of circadian rhythms is the suprachiasmatic nucleus (SCN), located in the hypothalamus of the brain. It does this mainly by controlling melatonin secretion, the main circadian hormone.

Health problems associated with circadian rhythm disruption include:

– Allergies
– Asthma
– Cardiovascular disease
– Hypertension
– Insomnia
– Jet lag
– Metabolic disorders
– Neurological disorders
– Psychiatric disorders
– Social jet lag
– Stroke
– Gastrointestinal disorders
– Rheumatic disorders
– Certain cancers

Other lifestyle factors may affect human health if diurnal rhythms are disrupted. For example, bright light at night, mistimed meals, and late-night arousal from exercise may alter synchronization cues for the circadian rhythm, causing a shift in metabolism and sleep. Consistent disturbances to daily rhythms may cause adverse health effects over time. Behaviors practiced at less optimal times of day affect nutrient sensing, glucose metabolism, and lipid metabolism. Disruptions in the circadian rhythm also reduce life expectancy. Furthermore, as individuals age, they become more sensitive to disruptions in circadian rhythms and less sensitive to synchronization techniques. This is especially true if disruptions occur in adolescence or early adulthood.

How to Support Circadian Rhythms

Maintaining circadian rhythms is an important action for long-term health. Certain markers, such as cortisol, melatonin, and body temperature, may help determine if an imbalance exists.

A few simple actions to take to maintain a balanced rhythm include:

• Avoid exercising late at night
• Avoid foods that can induce a phase shift (e.g., high-fat meals)
• Consume lots of antioxidant-rich fruits and vegetables, especially those rich in polyphenols
• Do not eat late at night, and aim to have the last meal 3-4 hours before bedtime
• Eat the biggest meals early in the day
• Follow a regular meal schedule within a restricted period (10 hours or less), as timed restricted feeding of the same high-fat meal was shown to produce better metabolic outcomes than eating throughout the day, and a 5-hour shift in meal timing has led to a similar shift in circadian rhythms
• Get a good night’s sleep and avoid night shift work when possible; or, commit to night shift work schedules fully
• Limit caffeine, which has been shown to shift circadian rhythms
• Aim for sunlight exposure during the day
• Minimize light exposure at night; or, wear blue-light-blocking glasses if exposed to bright electric light

In addition to generally maintaining a functional circadian rhythm, consider the impact of enzymes, digestion and absorption, and metabolism when deciding at what time to take certain supplements and medications. Before making any changes in the diet, supplementation, and lifestyle, talk to a doctor, nutritionist, dietician, or another member of the healthcare team. Personal options should be based on individual circumstances, conditions, medications, and health needs.