MR is frustrated that their morning glucose is almost always elevated. Since you have heard about the impact of “chronotype” on glucose, you ask them about eating patterns and explore whether they are early birds or night owls.
The 2024 American Diabetes Association (ADA) Standards of Care introduced the field of chrononutrition, the science of how our body’s 24-hour cycle (circadian rhythm), nutrition, and health interact. Growing evidence shows that factors, including when and type of food is eaten, hormones, genetics, exercise, sleep cycles, and a person’s daily light exposure, influence health and risk for metabolic disease.
When we consider a person’s chronotype, we realize that it’s not just “what” individuals eat that impacts metabolic health. Could “when” they eat and their chronotype be just as crucial for glucose regulation? Can we leverage this information to suggest modifications in the type of nutrients consumed throughout the day to support improved glycemia?
We have learned the association between circadian rhythm disruptions and metabolic disorders from people who perform shift work. Working in shift work and having type 2 diabetes is associated with increased A1c, neuropathy, and decreased psychological well-being.1 Glucose metabolism and tolerance follow a circadian rhythm throughout the day. Hormones, such as insulin and cortisol, cycle daily and regulate insulin sensitivity and glucose metabolism changes. Research suggests when food intake is out of sync with the daily cycle, this can reduce glucose tolerance and increase the risk of metabolic diseases such as type 2 diabetes, obesity, and cardiovascular disease.
“Meal timing and food nutrient components (chrononutrition) play an important role in regulating the circadian clock, enhancing metabolic health, and reducing the risk of type 2 diabetes.” 2
Post-prandial glucose response is affected by what and how much we eat and can vary based on the time of day the meal is consumed. Meal timing can affect type 2 diabetes, so it is important to consider timing in addition to composition alone. In a 2020 review article by Henry et al., they reported several different studies completed in individuals with type 2 diabetes and healthy subjects. These studies suggested both morning and late-night eating can contribute to the greatest glucose excursions. Eating after 8 pm was independently associated with an increase in A1C levels. Consuming more than a third of daily calories late in the evening led to higher post-meal glucose excursions and reduced morning glucose tolerance compared to other times of day. And a study of individuals with type 2 diabetes showed higher post-meal glucose trends after morning meals verses identical meals consumed throughout the day. These small studies suggest that modifying when a meal is consumed could reduce glycemia and the risk of diabetes. However, more extensive studies are needed to support causation and associate it with a person’s genetics and true chronotype.
Macronutrient meal composition and the time of day consumed may also play a role in chrononutrition. Whether it is a variation of calories consumed or manipulating different macronutrients from meal to meal, the relationship between food type and timing could affect glucose metabolism. Changes in insulin sensitivity throughout the day can affect post-meal glucose in response to varying carbohydrate quantity, quality, and rate of digestion. Davis et. Al, 2019 found that increased protein and lower carbohydrates at dinner meals reduce night post-prandial glucose compared to standard meals.
The key nutrition recommendations from the 2024 ADA Standards of Care are focused on individualizing eating patterns, meal plans, and dietary approaches. Research continues to evolve in this field, and there is much more to understand and validate. Most of the articles regarding chrononutrition referenced in the ADA Standards of Care are specific for type 2 diabetes, but we know circadian cycles and metabolism also play a role in type 1 diabetes. More research is needed to improve our understanding of why nutrients consumed at different times of day have differing effects, how this relates to the individual’s circadian biomarkers and genetics, and how it interplays with psychological factors that drive sleep cycles.
There is much to learn, but are there practical approaches we could consider implementing now? Yes! We can start by:
Blog contributed by nutrition expert Christine Craig, MS, RDN, CDCES
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