Effects of macronutrient manipulation on postprandial metabolic responses in overweight males with high fasting lipids during simulated shift work: A randomized crossover trial

Performance Nutrition for Physician Trainees Working Overnight Shifts: A Randomized Controlled Trial

PURPOSE

To compare acute effects of 2 dietary interventions with usual dietary habits on physician trainees' alertness during overnight shifts.

METHOD

This registered, controlled, block randomized crossover trial (NCT03698123) was conducted between October 2018 and May 2019 at Stanford Medicine. Physician trainees working at least 3 overnight shifts during a 1-week period were recruited. During the first night, participants followed their usual dietary habits. During the intervention nights (low carbohydrate-to-protein ratio and high carbohydrate-to-protein ratio interventions), participants received healthy dinners, snacks, water, and, upon request, caffeinated beverages, at the beginning of their shifts and were instructed to eat meals before 10 pm. The sequence of interventions on the second and third nights were block randomized across study weeks. Outcome measures (a priori) were overnight changes in validated measures of specific neurobehavioral dimensions: psychomotor vigilance, sensory-motor speed, working memory, and risk decision making, as well as self-reported sleepiness and work exhaustion.

RESULTS

Sixty-one physician trainees participated in this study. Compared with usual dietary habits, overnight changes in psychomotor vigilance scores (scale 0-1,000) improved by 51.02 points (95% CI: 12.08, 89.96) and sleepiness (scale 1-7) improved by 0.69 points (95% CI: 0.33, 1.05) under the low carbohydrate-to-protein ratio intervention. Compared with usual dietary habits, overnight changes in sleepiness (scale 1-7) improved by 0.61 points (95% CI: 0.25, 0.96) under the high carbohydrate-to-protein ratio intervention. Neither intervention had beneficial effects relative to usual dietary habits with respect to sensory-motor speed, working memory, risk decision making, or work exhaustion. There were no differences in outcomes between low carbohydrate-to-protein ratio and high carbohydrate-to-protein ratio interventions.

CONCLUSIONS

Dietary interventions may mitigate negative effects of physician trainee sleep deprivation during overnight shifts. Future studies are warranted to further examine the effectiveness of nutritional strategies on physician alertness during overnight shifts.

Chrononutrition in the management of diabetes

Circadian rhythms are 24-h cycles regulated by endogeneous molecular oscillators called the circadian clock. The effects of diet on circadian rhythmicity clearly involves a relationship between factors such as meal timings and nutrients, known as chrononutrition. Chrononutrition is influenced by an individual's "chronotype", whereby "evening chronotypes" or also termed "later chronotype" who are biologically driven to consume foods later in the day. Research in this area has suggested that time of day is indicative of having an influence on the postprandial glucose response to a meal, therefore having a major effect on type 2 diabetes. Cross-sectional and experimental studies have shown the benefits of consuming meals early in the day than in the evening on postprandial glycaemia. Modifying the macronutrient composition of night meals, by increasing protein and fat content, has shown to be a simple strategy to improve postprandial glycaemia. Low glycaemic index (GI) foods eaten in the morning improves glycaemic response to a greater effect than when consumed at night. Timing of fat and protein (including amino acids) co-ingested with carbohydrate foods, such as bread and rice, can reduce glycaemic response. The order of food presentation also has considerable potential in reducing postprandial blood glucose (consuming vegetables first, followed by meat and then lastly rice). These practical recommendations could be considered as strategies to improve glycaemic control, rather than focusing on the nutritional value of a meal alone, to optimize dietary patterns of diabetics. It is necessary to further elucidate this fascinating area of research to understand the circadian system and its implications on nutrition that may ultimately reduce the burden of type 2 diabetes.