A Randomised Double-blind Placebo-controlled Acute Trial of Encapsulated Lemon Balm Efficacy and Tolerance on Calmness and Mood During Periods of Cognitive Demand

Cognitive overload can be a common occurrence in an information saturated world (Eppler et al., 2008; Graf et al., 2021; Pass et al., 2004), and chronic cognitive overload is considered an initiating step in the emergence of various physical and emotional health concerns, likely due to high processing demands on the working memory neural system (Graf et al., 2021). Over time, psychological and physiological stress may arise, however current chemical interventions may be unsuitable for those experiencing mild-to-moderate levels of stress (Ghazizadeh et al., 2021). Indeed, long-term use of psychotropic medicines have previously been associated with a worsening of psychological symptoms (Bertuccioli et al., 2022). Therefore, identifying interventions for those experiencing mild-to-moderate stress will have strong public health implications for the prevention or reduction of symptoms. In addition, an opportunity for dietary supplementation as an over-the-counter option for those who do not wish to take chemical interventions is becoming a popular choice (Ghazizadeh et al., 2021; Bertuccioli et al. 2022).

The current study will employ a parallel, double-blind, randomised placebo-controlled trial, assessing the effect of a single dose intervention of lemon balm extract (or matched placebo) in young-to-middle-aged adults with moderate levels of perceived stress. Subjects will be pre-screened to determine eligibility using the perceived stress questionnaire, where scores between 14 to 26 are indicative of moderate stress, to provide a total of 130 participants. The study comprises a familiarisation visit followed by an acute test day at the Nutritional Psychology Unit based at the University of Reading. The familiarisation visit will allow participants to practice the cognitive battery, complete calmness and mood measures, and provide information on habitual diet (Epic-Norfolk FFQ) and general health and lifestyle patterns to confirm eligibility. On the acute test day, subjective calmness and mood ratings will be recorded at various timepoints throughout the day, beginning with an initial baseline measurement (0h), and then 1h, 3h and 5h after consuming an acute dose of lemon balm extract (300mg) or a matched placebo. At these same timepoints, a computer-based cognitive battery will be completed, consisting of several tasks assessing domains of executive function, attention and memory. On the acute test day participants will arrive fasted and will be provided with a standardised breakfast (two croissants and a glass of water) to be consumed prior to 0h baseline measures. A standardised lunch (cheese sandwich, packet of crisps, and water) will also be provided after the 3h timepoint.