Your Internal Clock Is Ticking: Why Body's Circadian Rhythm Is The Gatekeeper of Your Health

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The timing of your meals is as important as what you eat, say experts

You have eaten your weekly quota of colourful vegetables, basked in sunlight for the much-needed Vitamin D, and sweated it out in your home gym too. However, you are still falling short of your ideal weight or health goals. Despite eating textbook healthy food, deficiencies still show up in your monthly health reports.

Is there any other factor that influences how our body digests food and absorbs nutrients? It turns out it just might be our circadian rhythm.

What is circadian rhythm?

“The word circadian is derived from the Latin phrase ‘circa diem’ which means ‘around a day’. Circadian rhythm or body clock is an internal process regulating the sleep-wake cycle, endocrine and metabolic pathways of an organism in response to the external environment. It maintains a complete homeostatic balance. Suprachiasmatic Nucleus (SCN) located at the hypothalamus in the brain controls it,” says Sweedal Trinidade, senior dietetics officer at PD Hinduja National Hospital and Medical Research Centre in Mumbai.

The energy obtained from the food we eat is used to synthesise proteins, DNA, cell membrane components, polysaccharides, etc. Our body clock knows the time for food, digestion, sleep, and other functions. Any deviation from a normal pattern for a long time can disrupt the circadian rhythm, hamper digestion, and affect overall health in the long run.

The rat race

Is there any link between the circadian rhythm and nutrient absorption? Professor Anura Kurpad from the physiology and nutrition department at St John’s Medical College in Bengaluru said that a clear link has been established in rats.

“There is rat-based literature on the effect of circadian rhythms on nutrient absorption. This could be due to patterns in enzyme secretion by the stomach and pancreas, or due to the actual absorption of digested molecules like sugars into the intestinal cells. The latter — the circadian variability of transporters for glucose, fructose, and dipeptides— has been very elegantly demonstrated in rats. Obviously, it is difficult to do this in humans. The regulation of this variation might be done by a gene called the clock gene, or even by nerve or hormone control – a ‘high command’ in the hypothalamus of the brain,” he said.

The reason this happens, said the professor, is that animals have a sleep-wake cycle, and it makes sense to have the intestine work at peak efficiency when feeding is going on. “We get used to a timed meal pattern. Some studies in humans show that changing meal timing patterns can change the glucose cycles in the blood. In animals that have a mutation in the clock gene, circadian rhythms of glucose absorption get attenuated – this might be one of the reasons shift workers or those who do a lot of travel across time zones, are at risk of gaining weight (although the caveat is that the main reason for gaining is just disrupted eating patterns, snacking, etc),” he added.

Brain clock and heart activity

There is a connection between circadian rhythm and heart activity too, says Dr Rebecca Pinto, a physiotherapist and dietician. “For years, doctors and researchers have noticed that heart problems like fatal arrhythmias are more likely to occur at certain times of the day. Taking blood pressure medication in the evening seems to improve its effectiveness because it works with the body’s circadian rhythms. The reason for this has recently become clear: a genetic factor involved in the rhythm of the brain’s clock also controls the electrical activity in the heart,” she said.

Similarly, the time at which you eat your food affects how you lose weight, added Dr Pinto. “When your body is used to regular exercise, it gets used to fat loss and fat gain at different times of the day. Eating the wrong food at the wrong time can hamper your efforts in the gym,” she said.

Factors affecting circadian rhythm

Sweedal Trinidade listed the factors that affect circadian rhythm:

Genetic mutations
Working in shifts or jet lag
Blue light or light from electronic devices at late night
Lifestyle changes (partying or working till late hours)

Trinidade says that sleep-wake cycle disruption is one of the reasons for the rise in metabolic disorders nowadays. The other reasons are the easy availability of calorie-dense or processed foods and a sedentary lifestyle.

Inadequate sleep and vitamin deficiency

Paraj Primlani, founder of ParaFit and a certified nutritionist, says that people who get less than seven hours of sleep on average generally have deficiencies of vitamins A, D, and B1, as well as magnesium, niacin, calcium, zinc, and phosphorus. The body’s clock is responsible for more than just sleep and wakefulness. Other functions like hunger, mental alertness, heart regulation, and immunity also operate on a daily rhythm. Disrupting the body’s natural normal cycle can cause various health problems, he said.

Circadian rhythm and digestion

Dietician Mac Singh, who is the co-founder of the Fitelo app, says that our ancestors used to eat their last meal before sunset, and modern research supports that. “Your digestion system is at its full capacity during the daytime. Most enzymes and digestive juices are secreted during the daytime and that helps in better absorption of nutrients. As we move close to the sunset our digestive system becomes weaker. There is an all-time rise in digestive issues such as constipation and bloating. One of the major reasons for this is eating at the wrong time,” he said.

“Apart from digestion, we have seen an all-time rise in sleep disorders and anxiety. All these concerns are directly related to our circadian rhythm. Today, we hardly go out in the sun and that disturbs our biological clocks. Adding to that, artificial lighting everywhere further confuses the body’s clock. A disturbed biological clock confuses the digestive system regarding the secretion of digestive enzymes,” he added.