Study under review: Sugar rush or sugar crash? A meta-analysis of carbohydrate effects on mood.
As summer rolls around the corner, you can be sure parents are ready to stop their kids from drinking too much soda at little Billy’s pool party. As the title of the article under review suggests, acute sugar intake (or carbohydrates in isolation) has been commonly thought to lead to a ‘sugar rush’ (burst of energy) followed by a ‘sugar crash’ (fatigue from using up said burst of energy) though there is no strong scientific evidence to support this myth.
The ‘sugar rush’ notion was dispelled in the scientific community when a comprehensive 1995 meta-analysis demonstrated no effect of sugar on behavior or cognitive performance in children. Nonetheless, the myth survives and for almost 25 years after that meta-analysis, researchers continued to study the influence of sugar on mood. This occurred in the context of the U.S population, which uses soda, energy, and sports drinks as one of the top ten sources of energy in the country. More specifically, some studies investigating the interaction between mood and simple sugars have suggested changes in cognitive performance and emotional wellbeing.
One appealing hypothesis regarding carbohydrates (CHOs) and emotional well-being is the serotonin hypothesis. This hypothesis, whose details are depicted in Figure 1, postulates that CHO consumption leads to higher levels of the feel-good neurotransmitter serotonin in the brain as a result of greater tryptophan (a precursor to serotonin) availability. This is supported by reports of individuals suffering from mood disorders (i.e. depression, anxiety, etc.) that tend to self-medicate with CHO-rich meals. However, one study from the 1980s failed to observe increases in tryptophan or serotonin after eating, except in a protein-free meal. This tryptophan-increasing effect appears to be stopped if as little as 5% of the ingested CHO drink or meal is protein.
Other studies have demonstrated conflicting results, reporting no influence or even slightly detrimental effects on the overall relationship between mood and CHO intake. While reviews have recently covered the relationship between CHO intake and mood, studies have not been quantitatively (meta-) analyzed to determine which direction the evidence leans and to quantify how heterogeneous the literature really is. The authors of the study under review conducted a meta-analysis to fill this gap by quantitatively analyzing the short-term effects of isolated CHO intake on mood while considering potential confounding variables such as CHO dose and/or type, fasting interval, and any activity preceding mood assessment.
Carbohydrates are believed to influence behavior and mood. While some studies suggest carbohydrate intake will increase the release of the “feel-good neurotransmitter” serotonin and even boost cognitive performance, some report no influence, if not slightly detrimental effects. The study under review aims to quantify the effect and explain the conflicting results through a review and meta-analysis of results and confounding factors that may influence the putative interaction between CHO intake and mood.
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Other Articles in Issue #55 (May 2019)
NERD Mini: Food groups’ association with the risk of overweight and obesity
How much do certain food groups contribute to obesity risk? A recent systematic review and meta-analysis explored this question.
NERD Mini: The state of the evidence concerning A1 beta-casein
A1 beta-casein is a type of protein found in the milk of certain breeds of cattle. There's some evidence to suggest that this protein is associated with negative health outcomes. But how good is this evidence?
Examining coenzyme Q10 for migraine relief
The exact causes of migraine headaches aren't fully known, but part of the equation may involve mitochondrial problems. Could supplementing a major player in mitochondrial energy production help mitigate migraines?
Are we saffroning our way to mitigating diabetes?
Certain herbs and spices may have a beneficial impact on diabetes. We've covered lemon balm and cinnamon in the past. In this volume, we add saffron to the list of spices we've examined in the NERD.
Pomegranate's antioxidant capacity may be one of a handful of reasons it could help with both exercise performance and recovery. This recent clinical trial put pomegranate extract to the test by exploring its effects in cyclists.
Dietary carbohydrate for glycemic control: Does it matter in type 1 diabetes?
This randomized controlled trial adds to the scarce literature examining the medium-term effects of a lower carb diet in people with type 1 diabetes.
Gucci vs. Gap carbs
Quality matters when it comes to carbs. This series of meta-analyses explored what measures of carb quality are most useful for predicting health outcomes.