[Show abstract][Hide abstract] ABSTRACT: Cocoa flavanols (CF) positively influence physiological processes in ways that suggest their consumption may improve aspects of cognitive function. This study investigated the acute cognitive and subjective effects of CF consumption during sustained mental demand. In this randomized, controlled, double-blinded, balanced, three period crossover trial 30 healthy adults consumed drinks containing 520 mg, 994 mg CF and a matched control, with a three-day washout between drinks. Assessments included the state anxiety inventory and repeated 10-min cycles of a Cognitive Demand Battery comprising of two serial subtraction tasks (Serial Threes and Serial Sevens), a Rapid Visual Information Processing (RVIP) task and a 'mental fatigue' scale, over the course of 1 h. Consumption of both 520 mg and 994 mg CF significantly improved Serial Threes performance. The 994 mg CF beverage significantly speeded RVIP responses but also resulted in more errors during Serial Sevens. Increases in self-reported 'mental fatigue' were significantly attenuated by the consumption of the 520 mg CF beverage only. This is the first report of acute cognitive improvements following CF consumption in healthy adults. While the mechanisms underlying the effects are unknown they may be related to known effects of CF on endothelial function and blood flow.
Journal of Psychopharmacology 11/2009; 24(10):1505-14. DOI:10.1177/0269881109106923 · 3.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The notion that chewing gum may relieve stress was investigated in a controlled setting. A multi-tasking framework which reliably evokes stress and also includes performance measures was used to induce acute stress in the laboratory. Using a randomised crossover design forty participants (mean age 21.98 years) performed on the multi-tasking framework at two intensities (on separate days) both while chewing and not chewing. Order of workload intensity and chewing conditions were counterbalanced. Before and after undergoing the platform participants completed the state portion of the State-Trait Anxiety Inventory, Bond-Lader visual analogue mood scales, a single Stress Visual Analogue Scale and provided saliva samples for cortisol measurement. Baseline measures showed that both levels of the multi-tasking framework were effective in significantly reducing self-rated alertness, calmness and contentment while increasing self-rated stress and state anxiety. Cortisol levels fell during both levels of the stressor during the morning, reflecting the predominance of a.m. diurnal changes, but this effect was reversed in the afternoon which may reflect a measurable stress response. Pre-post stressor changes (Delta) for each measure at baseline were subtracted from Delta scores under chewing and no chewing conditions. During both levels of stress the chewing gum condition was associated with significantly better alertness and reduced state anxiety, stress and salivary cortisol. Overall performance on the framework was also significantly better in the chewing condition. The mechanisms underlying these effects are unknown but may involve improved cerebral blood flow and/or effects secondary to performance improvement during gum chewing.
[Show abstract][Hide abstract] ABSTRACT: In the absence of effective pharmacotherapy for diabetes there has been an increase in the use of, and research into, alternative treatment strategies. These include exercise, dietary interventions and the use of supplements including extracts of ginseng. Two separate, placebo-controlled, double-blind, cross-over studies investigating the effects of chronic ingestion of Panax ginseng (study 1 used G115, study 2 used Cheong Kwan Jang) on glycated Hb (HbA1c; study 1, n 18; study 2, n 11), fasting plasma insulin (study 1, n 17; study 2, n 12), fasting plasma glucose and postprandial response (following breakfast) (study 1, n 23; study 2, n 14) in healthy volunteers are reported. In both studies it was found that Panax ginseng had no effect on any gluco-regulatory parameter investigated. These results are not consistent with those reported for a diabetic sample (albeit using slightly different outcomes). These results would suggest that chronic use of Panax ginseng by non-diabetic individuals will have little long-term effect on glucose regulation. The benefits to glucose regulation associated with long-term ginseng use may only be present in populations with compromised glucose control; however, further research is needed to confirm such a speculation.
The British journal of nutrition 12/2008; 101(11):1673-8. DOI:10.1017/S0007114508123418 · 3.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The notion that chewing gum may relieve stress was investigated in a controlled laboratory experiment. The defined intensity stress simulator (DISS) is a multi-tasking platform which reliably induces stress and also includes performance measures. Using a partial crossover design 40 participants (mean age 22 years) underwent two intensities of the DISS while chewing and not chewing. Before and after completing the DISS participants completed the state portion of the State-Trait Anxiety Inventory, Bond-Lader visual analogue mood scales and a single stress visual analogue scale. Salivary cortisol levels were co-monitored. Baseline measures revealed that both levels of stress were effective in significantly reducing self-rated alertness, calmness and contentment while increasing self-rated stress and state anxiety. Cortisol levels fell during both levels of the stressor during the morning but this effect was reversed in the afternoon. Pre-post DISS changes (Δ) for each measure at baseline were subtracted from Δ scores under chewing and no chewing conditions. During both levels of stress the chewing gum condition was associated with significantly better alertness and reduced state anxiety, stress and salivary cortisol. Overall performance on the DISS was also significantly better in the chewing condition. The mechanisms underlying these effects are unknown but may involve neurohormonal interactions during the cephalic phase, improved cerebral blood flow and/or effects which were secondary to performance.
[Show abstract][Hide abstract] ABSTRACT: It is currently debated whether glucose facilitation of cognitive performance is due to differential targeting of hippocampal memory or whether task effort is a more important determinant. Using a placebo-controlled, double-blind, crossover 2(Drink: glucose/placebo)×2(Effort: ±secondary task) design, 20 healthy young adults’ recognition memory performance was measured using the ‘remember-know’ procedure. Two high effort conditions (one for each drink) included secondary hand movements during word presentation. A 25 g glucose or saccharine (placebo) drink was consumed 10 min prior to the task. The presence of a secondary task resulted in a global impairment of memory function. There were significant Drink×Effort interactions for overall memory accuracy but no differential effects for ‘remember’ or ‘know’ responses. These data suggest that, in some circumstances, task effort may be a more important determinant of the glucose facilitation of memory effect than hippocampal mediation. However, the phenomenon need to be further explored.
[Show abstract][Hide abstract] ABSTRACT: L-Theanine is an amino acid found naturally in tea. Despite the common consumption of L-theanine, predominantly in combination with caffeine in the form of tea, only one study to date has examined the cognitive effects of this substance alone, and none have examined its effects when combined with caffeine. The present randomised, placebo-controlled, double-blind, balanced crossover study investigated the acute cognitive and mood effects of L-theanine (250 mg), and caffeine (150 mg), in isolation and in combination. Salivary caffeine levels were co-monitored. L-Theanine increased 'headache' ratings and decreased correct serial seven subtractions. Caffeine led to faster digit vigilance reaction time, improved Rapid Visual Information Processing (RVIP) accuracy and attenuated increases in self-reported 'mental fatigue'. In addition to improving RVIP accuracy and 'mental fatigue' ratings, the combination also led to faster simple reaction time, faster numeric working memory reaction time and improved sentence verification accuracy. 'Headache' and 'tired' ratings were reduced and 'alert' ratings increased. There was also a significant positive caffeine x L-theanine interaction on delayed word recognition reaction time. These results suggest that beverages containing L-theanine and caffeine may have a different pharmacological profile to those containing caffeine alone.
[Show abstract][Hide abstract] ABSTRACT: It has previously been assumed that levels of caffeine typically found in decaffeinated beverages have no behavioural effects. However, recent findings from our laboratory indicate that caffeine doses as low as 9 mg have psychoactive properties which can endure for several hours. The current study aimed to establish the lowest active dose of caffeine and to ascertain the duration of any effects. Twenty participants took part in this randomised, placebo-controlled, double-blind, balanced-crossover study assessing the effects of three different doses of caffeine (2.5, 5, and 10 mg) administered in fruit juice. Cognitive performance, mood, autonomic activity and salivary caffeine were assessed pre-dose and at 1, 3, 6 and 9 h post-dose. Compared with placebo, performance was impaired by 2.5 mg, whilst 5 mg had negative effects on mood and mixed effects on performance and 10 mg improved performance. A number of these effects were apparent at 9 h post-treatment. Given that the average cup of decaffeinated coffee contains 3–5 mg caffeine, these results demonstrate that decaffeinated coffee is not inert as previously believed and this has implications for research which utilises decaffeinated coffee as placebo. Effects of caffeine are also longer-lasting than previously thought with effects apparent 9 h post-dose. This finding may offer an alternative explanation to withdrawal models for differing results in the literature pertaining to baseline performance in consumers and non-consumers of caffeine.
[Show abstract][Hide abstract] ABSTRACT: The present study aimed to systematically assess acute, dose-related behavioural effects of an extract of guaraná plant for the first time in humans. This double-blind, counterbalanced, placebo-controlled study (n=26) assessed the acute mood and cognitive effects throughout the day of four different doses (37.5 mg, 75 mg, 150 mg and 300 mg) of a standardised guaraná extract (PC-102). Assessment included the Cognitive Drug Research computerized test battery and Bond-Lader mood scales. Guaraná improved secondary memory performance and increased alert and content mood ratings. The two lower doses produced more positive cognitive effects than the higher doses. This research supports previous findings of cognitive improvements following 75 mg guaraná and provides the first exploration of different dose effects of guaraná in humans. The findings suggest that the effects cannot be attributed to caffeine alone.
Journal of Psychopharmacology 02/2007; 21(1):65-70. DOI:10.1177/0269881106063815 · 3.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Salvia officinalis (sage) has previously been shown both to possess in vitro cholinesterase inhibiting properties, and to enhance mnemonic performance and improve mood in healthy young participants. In this double-blind, placebo-controlled, crossover study, 30 healthy participants attended the laboratory on three separate days, 7 days apart, receiving a different treatment in counterbalanced order on each occasion (placebo, 300, 600 mg dried sage leaf). On each day mood was assessed predose and at 1 and 4 h postdose. Each mood assessment comprised completion of Bond-Lader mood scales and the State Trait Anxiety Inventory (STAI) before and after 20 min performance of the Defined Intensity Stress Simulator (DISS) computerized multitasking battery. In a concomitant investigation, an extract of the sage leaf exhibited dose-dependent, in vitro inhibition of acetylcholinesterase and, to a greater extent, butyrylcholinesterase. Both doses of sage led to improved ratings of mood in the absence of the stressor (that is, in pre-DISS mood scores) postdose, with the lower dose reducing anxiety and the higher dose increasing 'alertness', 'calmness' and 'contentedness' on the Bond-Lader mood scales. The reduced anxiety effect following the lower dose was, however, abolished by performing the DISS, with the same dose also being associated with a reduction of alertness during performance. Task performance on the DISS battery was improved for the higher dose at both postdose sessions, but reduced for the lower dose at the later testing session. The results confirm previous observations of the cholinesterase inhibiting properties of S. officinalis, and improved mood and cognitive performance following the administration of single doses to healthy young participants.