The impact of glycaemic load on cognitive performance: A meta-analysis and guiding principles for future research

Glucoregulatory status modulates acute cognitive effects of repeated low-glycaemic snack consumption in older adults: a decentralized randomized controlled trial

PURPOSE

This study examined the effects of differential postprandial glucose responses on cognition in healthy older adults in a real-life setting. We hypothesised that consumption of a lower GI snack would have favourable effects on cognitive functioning and that this effect would be more pronounced in individuals with better glucoregulatory status.

METHODS

Twenty-eight healthy adults, aged 50-65 years, underwent two intervention periods of three consecutive test days, consuming either a low-GI snack or a control snack twice a day in a cross-over design. Cognitive performance and self-reported cognitive ability, mood, and appetite were measured six times on each of the six test days using a mobile application. Continuous glucose monitoring (CGM) occurred throughout the study. Glycated haemoglobin (HbA1c) and fasting glucose levels were taken as markers of glucoregulatory status.

RESULTS

Consumption of the low-GI snack led to blunted post-prandial glucose responses but did not affect cognitive functioning. Significant interactions between the snack effect and glucoregulatory status were observed for Spatial Memory (p < 0.01), Symbol Search (p < 0.05), Composite Cognition score (p < 0.05), and a trend for subjective cognitive ability (p = 0.07), indicating poorer effects of the low GI snack in subjects with poorer glucoregulation. Fluctuations in blood glucose parameters did not mediate the cognitive effects of the snacks or cognitive function fluctuations throughout the test days.

CONCLUSION

We demonstrated that poorer glucoregulatory status negatively affected the cognitive responses to a low-GI snack intervention. This interaction between glucoregulatory status and treatment response was detectable in non-diabetic subjects with normal to mildly compromised glucose regulation.

TRIAL REGISTRATION

NCT05801731, 24-03-2023.

Acute effects of Hibiscus sabdariffa on blood pressure and cognitive function

INTRODUCTION

Hibiscus sabdariffa is well known for its blood pressure lowering properties, particularly in hypertensive individuals. To date, effects of hibiscus on cognitive performance have not been assessed, hence the current pilot study explored the acute effects of hibiscus consumption on cognitive performance and metabolic outcomes in overweight individuals.

METHODS

Twenty participants aged 35 ± 2.8 years with a BMI of 30 ± 1.2 (kg/m2) were recruited to a randomised, placebo-controlled crossover study. Participants received either a hibiscus-containing beverage or an inert placebo alongside a high carbohydrate breakfast. Metabolic and cognitive measures were assessed across a 2-hour postprandial period.

RESULTS

Consumption of the hibiscus drink significantly reduced postprandial glucose response compared to placebo after 30 and 45 min, with no change in blood pressure. Hibiscus consumption significantly attenuated the decline in delayed word recall on the visual verbal learning test. Additionally, there was a decrease in retroactive interference after hibiscus, suggesting that newly learned information interfered less with recall of previously learned information in comparison to placebo. Furthermore, non-significant improvements (p = 0.063) in executive function and pattern separation were observed following hibiscus consumption.

CONCLUSION

To summarise, this pilot study demonstrates that acute hibiscus consumption moderately affects aspects of memory and executive function, coupled with beneficial effects on postprandial glucose response. Further research is warranted to confirm these findings in larger sample sizes and to determine the effect of longer-term consumption of hibiscus on these outcomes.

Cognitive benefits of sleep: a narrative review to explore the relevance of glucose regulation

Sleep is essential for maintaining optimal health. Both sleep duration and quality have been linked to various physiological functions and physical and mental health outcomes. Nutrition has been shown to impact sleep parameters, from the nutrient composition of foods, such as tryptophan levels, to the physiological response to foods, such as the glucose response. However, the relationship between glycemic control and sleep, and its impact on next-day benefits, particularly on cognitive performance, remains complex and is not fully understood. This narrative review aims to explore the relationship between glycemia and sleep, and how it may affect cognitive performance the following day. The review includes data from observational and interventional studies, discussing mechanisms of action that may explain the modulating effect of glycemia on sleep and cognition. The evidence suggests that lower postprandial glucose and low variation of nocturnal glucose are associated with better sleep quality and shorter sleep onset latency. Good sleep quality, in turn, is positively associated with cognitive processes such as sustained attention and memory consolidation measured the next day after sleep. Future research opportunities lie in investigating the effects of modulating the glycemic and insulinemic responses through evening meals on sleep quality and next-day cognitive performance. Well-designed clinical trials involving healthy individuals are necessary to establish the effects of these interventions. Controlling glycemic and insulinemic profiles through the evening meal may have significant implications for improving sleep quality and cognitive performance, with potential impact on individual mental health, productivity, and overall well-being.

Association of Plant-Based Dietary Patterns with Activities of Daily Living Disability in Older Adults Based on a 10-Year Cohort Study

BACKGROUND

In the context of population aging, activities of daily living (ADL) disability has brought great challenges to the health of the elderly. The relationship between plant-based dietary patterns and the health of the elderly has been widely discussed. However, few studies have explored the correlation between plant-based dietary patterns and ADL disability in older adults.

METHODS

We included 2004 participants from the Chinese Longitudinal Health Longevity Survey (CLHLS). The Simplified Food Frequency Questionnaire was used to measure Plant-Based Diet Index (PDI), healthy Plant-Based Diet Index (hPDI), and unhealthy Plant-Based Diet Index (uPDI). A Cox proportional hazards model was used to assess associations between plant-based dietary patterns and ADL disability in older adults and to explore age differences in these associations.

RESULTS

uPDI and hPDI showed nonlinear associations with ADL disability. Following covariate adjustments, older adults in the highest tertile of the hPDI have a lower risk of ADL disability than those in the lowest tertile (HR = 0.61). Older adults in the highest tertile of the uPDI have a higher risk of ADL disability than those in the lowest tertile (HR = 1.33). Subgroup analyses showed that hPDI was more protective against ADL disability in those under 80 years of age, whereas uPDI was only significantly associated with an increased risk of ADL disability in those under 80 years of age.

CONCLUSIONS

Increasing the intake of healthy plant-based diets and reducing the intake of unhealthy plant-based and animal-based diets can help prevent and improve ADL disability in the elderly.

Associations between breakfast skipping and outcomes in neuropsychiatric disorders, cognitive performance, and frailty: a Mendelian randomization study

BACKGROUND

Prior studies have identified a correlation between breakfast skipping and a heightened risk of mental health issues. This investigation aimed to employ a Two-Sample Mendelian Randomization (MR) approach to explore the potential causal links between breakfast skipping and various psychiatric, neurological disorders, cognitive performance, and frailty.

METHODS

Utilizing data from genome-wide association studies within European demographics, this research scrutinized the association between breakfast habits and several neuropsychiatric conditions and physical health outcomes, including Alzheimer's disease (AD), Attention Deficit Hyperactivity Disorder (ADHD), Bipolar Disorder (BD), Major Depressive Disorder (MDD), Narcolepsy, Insomnia, cognitive performance, and frailty. In this MR analysis, the Inverse Variance Weighted (IVW) method was primarily utilized for evaluation. Outcomes were reported as Odds Ratios (OR) and regression coefficients (β), and underwent validation through False Discovery Rate (FDR) corrections, thereby offering a rigorous evaluation of the effects of breakfast habits on both mental and physical health dimensions.

RESULTS

Findings demonstrate a significant causal link between skipping breakfast and an increased risk of ADHD (OR = 2.74, 95%CI: 1.54-4.88, PFDR = 0.003) and MDD (OR = 1.7, 95%CI: 1.22-2.37, PFDR = 0.005). Conversely, no substantial causal associations were identified between breakfast skipping and AD, BD, narcolepsy, or insomnia (PFDR > 0.05). Moreover, a notable causal relationship was established between skipping breakfast and a reduction in cognitive performance (β = -0.16, 95%CI: -0.29-0.04, PFDR = 0.024) and an increase in frailty (β = 0.29, 95%CI: 0.12-0.45, PFDR = 0.003).

CONCLUSION

The MR analysis reveals that skipping breakfast is associated with an increased risk of ADHD, MDD, decreased cognitive performance, and greater frailty, while showing no associations were found with AD, BD, narcolepsy, or insomnia. These findings warrant further investigation into the underlying mechanisms and emphasize the importance of regular breakfast consumption for mental and physical well-being.

No food for thought-How important is breakfast to the health, educational attainment and wellbeing of school-aged children and young people?

There have been reports from teachers of pupils in the United Kingdom arriving at school hungry. Poor nutritional intake during childhood can increase the risk of developing both short- and long-term health problems. Breakfast consumption has been associated with several outcomes including better diet quality and healthier weight status. Nevertheless, skipping breakfast is a frequent behaviour in young people, particularly adolescents, and those from lower socio-economic groups, who are less likely to meet dietary recommendations and nutritional targets. The aim of this narrative review is to explore the contribution of breakfast consumption at home or at school and the impact of breakfast skipping on nutrient intakes in school-aged children (aged 4-18 years), and their effect on weight and cardiometabolic health. We will also summarise evidence for a link with cognitive function and educational attainment. A broadly positive effect of breakfast intake on diet quality, weight status and school-related outcomes was found in the literature, although inconsistencies in findings and methodological limitations within the evidence base are notable. Further research is warranted to better understand impact of breakfast intake and school breakfast provision on longer-term learning, educational attainment and health outcomes. This also needs to consider the cost benefit, type of breakfast and any unintended consequences such as encouraging multiple breakfasts. Breakfast consumption could improve the nutritional intakes of the most vulnerable young people and may help to address inequalities in educational outcomes at least in the short term.

Acute effects of drinks containing blackcurrant and citrus (poly)phenols and dietary fibre on postprandial glycaemia, gut hormones, cognitive function and appetite in healthy adults: two randomised controlled trials

(Poly)phenol (PP)-rich blackcurrant (BC) extracts reduce postprandial glucose concentrations. Combinations with other fruit (poly)phenols and fruit fibre may enhance the effect. This study investigated the acute effects of combinations of BC extracts, high (H-BC) and low (L-BC) (poly)phenol concentrations, sweet orange extracts (SO) and fibre-rich orange pulp (F) in reducing postprandial glycaemia. In two randomised, double-blind, crossover design studies, healthy participants consumed seven types of 200 mL beverages: in the GLU-FX trial, H-BC (1600 mg PP); L-BC (800 mg PP); SO (800 mg PP); BC + SO (1600 mg PP) or CON (placebo); in the GLU-MIX trial, BC + F (800 mg PP), F (1.5 g fibre), or CON2 (placebo), immediately followed by consumption of 75 g available carbohydrate (starch and sugars). Blood was sampled at baseline and postprandially to measure changes in glucose, insulin, and gut hormones; appetite changes were assessed by visual analogue scales and, in GLU-MIX, ad libitum food intake and cognitive function were assessed. Twenty-nine and thirty-seven adults completed GLU-FX and GLU-MIX, respectively. L-BC reduced early postprandial glycaemia (0-30 min) with no differences in glucose incremental Cmax or total glycaemic response. No significant effect was observed following other drinks relative to CON. L-BC and H-BC drinks inhibited insulin secretion up to 30 min and GIP up to 120 min. In GLU-MIX, BC + F improved some indicators of cognitive function but not all. Measures of appetite were unaffected. The impact of (poly)phenol-rich BC extracts on total postprandial glycaemia in healthy participants was minimal and not enhanced when administered in combination with an orange (poly)phenol extract or orange pulp. Clinical Trials registered at https://www.clinicaltrials.gov: NCT03184064 (GLU-FX) and NCT03572296 (GLU-MIX).

A multimeal paradigm producing a low glycemic response is associated with modest cognitive benefits relative to a high glycemic response: a randomized, crossover trial in patients with type 2 diabetes

BACKGROUND

Type 2 diabetes (T2DM) and poor glucose regulation in the immediate postprandial period are both associated with impairments in cognitive function. There is evidence that foods that generate a better postprandial glycemic response, such as low GI foods (which produce a lower glycemic peak, less variability, and a more sustained decline), are associated with cognitive benefits over the morning. However, the potential impact of consuming multiple meals of this nature over the course of a day on cognition in T2DM has not been explored.

OBJECTIVES

The primary aim of this research was to investigate whether a multimeal paradigm producing a low glycemic response was associated with cognitive benefits in patients with noninsulin-dependent T2DM relative to a multimeal paradigm producing a high glycemic response.

METHODS

Twenty-five adults with noninsulin-dependent T2DM (mean age: 57 y) consumed 2 multimeal profiles consisting of a breakfast, lunch, and afternoon snack on 2 separate test days following a randomized, counterbalanced, crossover design. The 2 conditions were a low GI profile (LGIP) and a high GI profile (HGIP).

RESULTS

Cognitive function, glycemic response, mood, and satiety were assessed over the day from 8:30 to 17:00. Overall, there were limited cognitive effects. However, there was evidence for cognitive benefits in the period before lunch, as demonstrated by better global cognitive and executive functions for the LGIP relative to the HGIP. No clear effects were observed for mood.

CONCLUSIONS

This study shows that a multimeal paradigm producing a low glycemic response was associated with some benefits for cognitive function in patients with T2DM.

CLINICAL TRAIL REGISTRY REFERENCE

NCT03360604 (clinical trial.gov).