The Effects of Carbohydrates, in Isolation and Combined with Caffeine, on Cognitive Performance and Mood—Current Evidence and Future Directions

Abstract

This review examines the effects of carbohydrates, delivered individually and in combination with caffeine, on a range of cognitive domains and subjective mood. There is evidence for beneficial effects of glucose at a dose of 25 g on episodic memory, but exploration of dose effects has not been systematic and the effects on other cognitive domains is not known. Factors contributing to the differential sensitivity to glucose facilitation include age, task difficulty/demand, task domain, and glucoregulatory control. There is modest evidence to suggest modulating glycemic response may impact cognitive function. The evidence presented in this review identifies dose ranges of glucose and caffeine which improve cognition, but fails to find convincing consistent synergistic effects of combining caffeine and glucose. Whilst combining glucose and caffeine has been shown to facilitate cognitive performance and mood compared to placebo or glucose alone, the relative contribution of caffeine and glucose to the observed effects is difficult to ascertain, due to the paucity of studies that have appropriately compared the effects of these ingredients combined and in isolation. This review identifies a number of methodological challenges which need to be considered in the design of future hypothesis driven research in this area.

Sugar rush or sugar crash? A meta-analysis of carbohydrate effects on mood

“…Considering that no beneficial effects of CHOs on mood were identified, our metaanalysis calls into question the existence of a mood-boosting mechanism (serotonin-based or otherwise) related to CHO consumption. In fact, the validity of the CHO-serotonin mechanism and, by extension, the CHO-mood relationship has received criticism and has been difficult to replicate in experimental settings (for reviews, see Benton, 2002;Boyle et al, 2018;van de Rest et al, 2017). Interestingly, even in studies that have found CHO to influence serotoninergic activity, it is suggested that this effect is observable only under specific conditions (e.g., stress; Markus, 2007), and for clinical populations rather than healthy individuals (for a review, see Wurtman and Wurtman, 2018), calling into question the validity of the CHO-mood relationship for the general population.…”

“…Over the last three decades, an increasing number of empirical reports have suggested that ingestion of CHOs does not lead to any pronounced increases in subjective mood and overall affect, but can even have detrimental effects on mood (Adan and Serra-Grabulosa, 2010; Brody and Wolitzky, 1983;Duckworth et al, 2013;Giles et al, 2012;Harte and Kanarek, 2004;Howard and Marczinski, 2010;Jones and Sünram-Lea, 2008;Meikle et al, 2004;Miller et al, 2013Miller et al, , 2014O'Neal et al, 2013;Owen et al, 2013;Qin et al, 2017;Hammersley, 1998, 1995;Riby et al, 2004;Scholey et al, , 2009Scholey and Fowles, 2002;Scholey and Kennedy, 2004;Seo et al, 2014;Stollery and Christian, 2013;Sünram-Lea et al, 2011;Ullrich et al, 2015;van der Zwaluw et al, 2014;Zacchia et al, 1991). Researchers have acknowledged the complicated nature of the results and have challenged the reliability of CHO effects on mood (Benton, 2002;Boyle et al, 2018;van de Rest et al, 2017). Whereas CHO effects on cognition are strong and well-documented (Messier, 2004;Riby, 2004;Smith et al, 2011), the effects of CHO administration on mood are not as dependable, a finding that could be attributed to a number of factors including the diverse methodologies employed by researchers to assess CHO-mood interactions.…”

“…This poses a problem for the investigation of mood effects as activity prior to mood assessment is likely to affect mood ratings. Furthermore, as the facilitation effects of CHOs are suggested to be more reliable in the cognitive domain (for a review, see Boyle et al, 2018), some studies assess mood as a variable of secondary importance, without appropriate justification as to why such measures are included and no a priori hypotheses with regards to expected mood outcomes. More importantly, the focus on cognitive outcomes means that sample sizes are selected based on the number of participants needed to observe CHO-related cognitive facilitation.…”

“…There have been several reviews on the CHO-mood relationship (Benton, 2002;Benton and Donohoe, 1999;Benton and Nabb, 2003;Boyle et al, 2018;Gibson and Green, 2002;van de Rest et al, 2017) Therefore, we will provide an overview of the methodologies used in studies assessing CHO-mood interactions and aim to systematically disentangle the effect of moderating variables on the CHO-mood relationship. First, if the effects of CHOs are related to fluctuations in serotonin synthesis and availability, we expected that strong CHO-mood interactions would appear beyond the first hour post-CHO ingestion.…”

Prevalence and Perceived benefits of energy drink Consumption in medical students

“…11 It suggests that there is some association between the cognition-regulatory effects of caffeine and glucose when used in unison. 12 Some energy drinks also contain Amphetamine which causes elevation of mood & euphoria. 5 High doses of Amphetamine can lead to delusions & simulate schizophrenia-like conditions.…”