Written by Ambika Nair

Have you ever wondered why we eat three meals a day, or why our bodies are able to fast as we sleep?

The term Chrononutrition refers to how we sync our dietary intake with our biological circadian clock. This coordination is key for us to be able to maintain sleep, metabolism, hormone release, immune function, and other crucial bodily processes linked to external stimuli. The suprachiasmatic nucleus (SCN) in the hypothalamus of our brains is the “master clock”, and the coordinator of these functions. Disruption of a key aspect to this coordination–dietary intake–may lead to long-term health complications.

A disrupted dietary-circadian clock is most prevalent in shift workers, especially those working odd hours in the healthcare industry. Around 70% of shift workers are considered to be overweight or obese. What is the science behind this phenomenon?

The SCN is the central pacemaker control center that releases electrical signals, proteins, and hormones. Expression levels fluctuate throughout a twenty-four hour period based on our visual stimulus from the light and dark environments. The release of these signals may activate other centers of the brain to coordinate body functions throughout the day. Specifically, the arginine vasopressin (AVP) neuropeptides of the SCN play a crucial role in signaling to control centers of circadian feeding and drinking rhythmic cycles (Ibid).

In a balanced cycle, the SCN works to maintain anabolic functions of the body’s organs while it is at rest. During the day, the body maintains catabolic functions including higher metabolic function and energy release through exercise. However, when the body becomes accustomed to irregular activity cycles throughout the day, it can lead to a disruption of these pathways. Notably, shift-workers who work late hours of the night into the early morning are not able to maintain adequate anabolic- restoration functions to reset for a twenty-four hour period. Sufficient amounts of the hormone leptin (satiety) aren’t reached while the hormone Ghrelin (hunger) increases. This still has not been properly researched. As a result, most shift workers find themselves hungry and snacking through the odd hours of night shifts. This irregular hormone production–along with a desynchronized metabolism during night hours–leads to rapid deposition of fats, weight gain, and chronic obesity issues.

Additionally, most shift workers find themselves eating foods high in carbohydrates during night hours. Cyclically, the body stores fat and metabolizes glucose at its highest rates during the day, while it stores glucose and metabolizes fats during night hours. Shift workers experience lower tolerance to fats and carbs because of the alteration in eating patterns. Insulin fluctuation in the body is heavily dependent on chrononutrition timing. Not enough time is given to the body to reset its insulin metabolism before breakfast for many shift workers. This can lead to increased weight gain and diseases such as dyslipidemia, hypertension, diabetes, and coronary heart disease.

In the United States, more than 15% of American workers work irregular night shift hours. In a study conducted by the American Journal of Medicine, healthcare ranked fifth in industries with the highest obesity rates, at 32% . Working night shifts increases the risk of obesity by 23%, and the risk of abdominal obesity by 35%.  It is important to understand the underlying connection between chronic health conditions and shift workers, specifically in healthcare.

Shreela Sharma, author and professor at the UTHealth School of Public Health, notes that “people who take care of others on a regular basis are generally less likely to take care of themselves. The focus of hospitals is on patient care, so sometimes the workers’ own care can take a back seat.”

It is true that the health of healthcare workers comes second to that of their patients. The implications of the industry on their own well-being is something we tend to overlook. However, the reality is that this problem becomes harder to ignore once it takes shape as a chronic health disorder. Working around the clock, and during night shifts–unsynchronized with the circadian rhythm–is mandatory for most professionals in the healthcare setting in order to provide continuous patient support. How can this lifestyle work to balance itself against the odds of accruing life-altering conditions? During the height of the COVID-19 pandemic, healthcare workers found themselves struggling more than ever with this circadian disruption. As mentioned, the proper maintenance of a twenty-four hour cycle between diet, hormonal balance, and immune system, is interconnected. Recently, research has been done on the crucial role the circadian rhythm plays in maintaining the body’s defenses against COVID-19. The dietary and sleep imbalance in shift workers result in a lower immunological response for healthcare workers towards the coronavirus (frontiers).

It is incredibly difficult to maintain a night work schedule, and most of the time the body cannot fully adjust and synchronize its pathways to this shift. A 2018 study on nurses’ dietary behaviors during night shifts found there to be higher intakes of caffeine and snacking behaviors, and a lower intake of liquids. After a survey done at the Houston Hospital, it was seen that an alarming 78% of hospital employees were overweight or obese. The high demand for healthcare workers to work nights, disrupting their circadian integrity, is an incredibly crucial factor to take into consideration when evaluating these statistics.

On top of this, working through an imbalanced cycle and a stressful work environment impacts inadequate hormone levels, psychological imbalance, and decision making. Some of these psychological conditions may include depression, insomnia, anxiety, and burnout syndrome. Nurses are a very high risk population for depressive episodes, partly resulting from the nature of their work shifts. In a Chinese study in 2014, it was found that nurses working irregular night shifts had a statistically significant higher probability of clinical depressive conditions in comparison to those who were not on such a schedule. Along with a shift in psychological well-being, healthcare workers working night shift hours for extended periods of time are seen to have increased levels of drug, tobacco, and alcohol consumption after work. Making unhealthy lifestyle choices as a consequence of circadian misalignment psychological dysfunction may offer an explanation for chronic health conditions in shift workers.

The average night shift healthcare worker finds themselves skipping breakfast after a long night shift, or deciding to sleep right after their meal. Breakfast plays a very crucial role in regulating chrononutrition for the next 24-hour circadian cycle, and works to determine the rhythm of bodily functions for that day. When this meal is skipped, dysfunctions of metabolism and the gastrointestinal tract systems can occur. Additionally, weak resetting of insulin secretion is strongly brought about by an insufficient fasting period before a breakfast meal, and leads to irregular glucose tolerance. Consequently, diseases such as diabetes, hypertension, and coronary heart disease are associated with skipping breakfast.

It may seem like a confusing conundrum for shift workers to overcome. On one hand,  it is important to eat a meal for breakfast, but on the other, breakfast and snacking throughout the night shift too close together is destructive for glucose tolerance. What kind of changes can healthcare workers make to prevent the onset of chronic illness? What changes can the healthcare industry make to prevent the onset of chronic illness in shift workers?

For one, foods rich in protein are more satiating than carbohydrates, which tend to onset quicker sleepiness. Additionally, the body is much more capable of metabolizing proteins during night hours in comparison to carbohydrates. A huge contributor to health conditions in shift workers is the inaccessibility to healthy foods during late hours in a hospital setting. Some hospitals have begun to utilize programs for healthcare workers to attain adequate nutrition while on-call. However, this is still something that is heavily overlooked. Currently, there are not enough policies in place in the U.S. that assure shift workers adequate break time to refuel with nutritious snacks throughout the shift. In other countries, such as Sweden, they have already begun to implement these policies for healthcare workers.

Unfortunately, there is not enough research at the moment of the circadian effects of meal skipping and late night snacking on the mental and physical well-being of healthcare workers. Most of the conclusions  drawn are a result of the physical and mental ailments we are witnessing. It is important that the wellbeing of our healthcare providers is not forgotten, to ensure these heroes can live their lives to the best of their abilities. The push for nutritional science research in recent times is a hopeful stepping stone towards identifying and finding solutions to the somewhat forgotten effects of a nuanced diet on human health.