Chrono-Nutrition: What is it and Does it Affect Cardiac Health?
Chrono-nutrition is a relatively new field of research in nutritional epidemiology. It encompasses three fields of eating behaviour: timing, frequency and regularity. Circadian rhythm misalignment can occur due to a variety of circumstances. Today, people often take part in activities that are misaligned with their circadian rhythm and the natural light-dark cycle. We find ourselves having irregular eating patterns, often due to external pressures to conform to social and work schedules. Eating food at different time points during the day can result in a misalignment between the sleep-awake, fasting-feeding cycles, and the light-dark cycle. This can subsequently disrupt the natural rhythm of physiologic processes such as glucose, lipid metabolism and blood pressure. Eventually, circadian misalignment can result in an increased risk of developing cardiovascular disease and type 2 diabetes.
What Circadian Rhythms and Chronotypes?
Cardiac Rhythms: Circadian rhythms are a period of approximately 24 hours, donating the physiological and behavioural processes of a living being. This includes animals, plants, fungi and cyanobacteria. Circadian rhythms are generated by an endogenous clock, but can be modulated by external signals such as sunlight and temperature.
Chronotypes: A person’s chronotype is the circadian typology of that particular person, which is a behavioural indicator of their internal circadian clock system. Based on a person’s chronotype people can be labelled as morning or evening people. A morning chronotype denotes someone who goes to sleep earlier and wakes earlier. In contrast, an evening chronotype denotes someone who goes to sleep later and wakes later. Both genetic variations and environmental factors influence the distribution of chronotypes in a given population.
The Link Between Chronotypes and Dietary Intake
Chrono-nutrition, the timing of dietary intake, may be implicated by a person’s chronotype, and thus has an impact on the timing of energy and nutrient intake. It is currently unknown whether a person’s chronotype is determined by their eating patterns or dietary intake, or whether your chronotype influences your diet. Literature and research on this topic is currently emerging and we are far from understanding the link between chronotype and diet, and how chrono-nutrition can affect cardiometabolic health. A review published in ‘Advances in Nutrition’ in January 2019 provides an overview of recent epidemiologic research on chronotype, and its association with dietary intake, eating behaviour and cardiometabolic health.
People with a morning chronotype consumed a mean of 0.25 more servings of fruit and 0.13 more servings of vegetables each day, compared with people with an evening chronotype.
Evening chronotypes were also associated with a lower intake of whole grains, rye, potatoes, and vegetables and roots, whereas intake of wine and chocolate was higher.
Intakes of alcohol and sucrose were also higher, whereas intakes of carbohydrates, protein, fibre, folic acid and sodium were lower.
Evening chronotypes were more likely to be smokers, physically inactive and have lower perceived health.
People with evening chronotypes have been reported to have lower energy and macronutrient intakes in the morning compared to people with morning chronotypes.
By contrast, in the evening, evening chronotypes reported higher intakes of energy, sucrose, fat, and saturated fatty acids than did morning chronotypes.
The Association Between Chronotype and Cardiovascular and Cardiometabolic Disease
Cardiovascular: Circadian misalignment has long been recognised as a risk factor for the development of cardiovascular diseases. This misalignment has largely been studied in shift work, however, more recently research has suggested that even a mild circadian misalignment, minor shifts between the sleep-awake cycle, is detrimental to health in non-shift workers.
It is known that cerebrovascular and cardiovascular events exhibit a bimodal pattern. Strokes follow a circadian rhythm with a major morning peak and a secondary early evening peak. Scientists have suggested that this circadian rhythm may be affected by exogenous factors such as eating behaviour and physical activity. As such, a person’s chronotype may correlate with cerebrovascular and cardiovascular disease risk. In one study, people with an evening chronotype were shown to have a 1.3-fold increased risk of arterial hypertension, a faster resting heart rate, and a lower systolic blood pressure, serum total cholesterol, and LDL cholesterol than people with a morning chronotype. Furthermore, an evening chronotype has also been related to lower high-density lipoprotein (HDL) cholesterol, good cholesterol, concentrations.
Alterations in when you eat can also increase the risk of metabolic diseases. Studies have shown that, despite consuming the same calories, people that eat later lose less weight that people who eat earlier in the day. Similarly, people given a bigger breakfast and a smaller dinner had greater weight loss, a greater reduction in waist circumference and improved metabolism compared to people given a smaller breakfast and a larger dinner.
Taken together, this evidence implies that chronotypes may modulate physiologic processes linked to cardiovascular health, including heart rate, blood pressure, and blood lipid concentrations. It remains to be elucidated whether variations in chronotype during childhood or adolescence could influence the path towards cardiovascular disease risk factors later in life, and whether this effect could be modulated by chrono-nutrition.
Cardiometabolic: Research on irregular meal patterns suggests that eating meals irregularly is associated with a higher risk of metabolic syndrome and cardiometabolic risk factors, which includes diabetes, heart disease and stroke. In fact, scientists have shown in a RCT in lean and obese women that consuming meals regularly for two weeks in comparison to an irregular meal pattern, led to a beneficial impact on cardiometabolic risk factors such as, lower peak insulin, lower fasting total and LDL-cholesterol.
Type 2 Diabetes: Glucose tolerance generally reduces during the course of the day, reaching its lowest point in the evening. Thus, glucose metabolism also follows a circadian rhythm. The circadian misalignment induced in shift workers is believed to underlie their raised postprandial glucose and insulin concentrations and an increased risk of impaired glucose tolerance and type 2 diabetes. Furthermore, scientists have shown that circadian misalignment can lead to some subjects to exhibit postprandial glucose responses similar to the range observed in prediabetes. Together, such findings implicate circadian misalignment as a predisposing factor to the development of type 2 diabetes. In one study, people with an evening chronotype were shown to have a 2.5-fold increased risk of type 2 diabetes than individuals with a morning chronotype. Interestingly, sex differences have also been implicated, wherein an evening chronotype was related to diabetes in men and to metabolic syndrome in women. As a person’s chronotype may affect dietary intake and eating patterns, which in turn could influence glucose metabolism and potentially lead to type 2 diabetes and metabolic syndrome.
There is limited evidence of the role of chrono-nutrition on cardiovascular and cardiometabolic disease, however this evidence does suggest that consuming meals irregularly is adversely associated with cardiovascular and cardiometabolic risk. Scientific evidence is providing increasing knowledge into the relation between chronotype, diet and cardiometabolic health. Overall, studies suggest that an evening chronotype is associated with a lower intake of fruits and vegetables and higher intake of energy drinks, alcoholic, sugary, and caffeinated beverages, as well as higher energy intake from fat. A limited number of studies also demonstrate that an evening chronotype is potentially related to changes in timing of food intake, irregular eating and meal skipping, particularly breakfast.
Hence, meal timing can play a critical role in determining health outcomes and can potentially be used to foresee obesity, cardiovascular and cardiometabolic diseases. Chrono-nutrition thus has a vital role in coordinating food intake with the body’s daily rhythms, particularly given that a variety of enzymes involved in lipid and glucose metabolism are regulated according to circadian cycles. As such, any disruption to this rhythm (as in shift work or jet lag) can alter the body’s rhythm and increase the risk of disease.
Working with our bodies natural rhythm will allow us to maintain or restore health, simply eating meals at the appropriate times, getting exposure to daylight during the day and going to bed early have important ramifications for our future health and wellbeing.
However, there is still a need for more large-scale studies to further advance our understanding of the association between chrono-nutrition and long-term cardiometabolic health. This will potentially guide the development of health-promotion strategies aimed at preventing and treating chronic diseases based on a person’s chronotype.
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