Fiona Dodd

Monoterpenoid extract of sage (Salvia lavandulaefolia) with cholinesterase inhibiting properties improves cognitive performance and mood in healthy adults

Extracts of sage (Salvia officinalis/lavandulaefolia) with terpenoid constituents have previously been shown to inhibit cholinesterase and improve cognitive function. The current study combined an in vitro investigation of the cholinesterase inhibitory properties and phytochemical constituents of a S. lavandulaefolia essential oil, with a double-blind, placebo-controlled, balanced crossover study assessing the effects of a single dose on cognitive performance and mood. In this latter investigation 36 healthy participants received capsules containing either 50 µL of the essential oil or placebo on separate occasions, 7 days apart. Cognitive function was assessed using a selection of computerized memory and attention tasks and the Cognitive Demand Battery before the treatment and 1-h and 4-h post-dose. The essential oil was a potent inhibitor of human acetylcholinesterase (AChE) and consisted almost exclusively of monoterpenoids. Oral consumption lead to improved performance of secondary memory and attention tasks, most notably at the 1-h post-dose testing session, and reduced mental fatigue and increased alertness which were more pronounced 4-h post-dose. These results extend previous observations of improved cognitive performance and mood following AChE inhibitory sage extracts and suggest that the ability of well-tolerated terpenoid-containing extracts to beneficially modulate cholinergic function and cognitive performance deserves further attention.

Influence of dietary nitrate supplementation on physiological and cognitive responses to incremental cycle exercise

Dietary inorganic nitrate supplementation causes physiological effects which may enhance exercise tolerance. However it is not known whether nitrate might alter cognitive function during exercise. In a double-blind, cross-over study, sixteen subjects ingested either nitrate-rich beetroot juice or a placebo and completed a continuous cycle exercise test involving 20min stages at 50% and 70% V˙O2peak and a final stage at 90% V˙O2peak until volitional exhaustion. Cognitive tasks were completed before, during and after exercise. In the dietary nitrate condition: plasma [nitrite] increased (p<0.01), systolic blood pressure decreased (p<0.05) and there was a trend for a reduced oxygen uptake at 50% V˙O2peak. Tissue oxygenation improved across exercise intensities and exercise tolerance was greater at 90% V˙O2peak (p<0.05). Rating of perceived exertion, energy levels and cognitive performance were similar between conditions with mental fatigue being evident from 70% V˙O2peak onwards (p<0.05). Dietary nitrate supplementation enhanced short-term endurance exercise performance with concomitant mental fatigue but did not improve cognitive performance post-fatigue.

Vitamins and psychological functioning: a mobile phone assessment of the effects of a B vitamin complex, vitamin C and minerals on cognitive performance and subjective mood and energy

Despite being widely consumed, the effects of multi‐vitamin supplements on psychological functioning have received little research attention.

Multivitamins and minerals modulate whole-body energy metabolism and cerebral blood-flow during cognitive task performance: a double-blind, randomised, placebo-controlled trial

BackgroundThe brain is by far the most metabolically active organ in the body, with overall energy expenditure and local blood-supply closely related to neural activity. Both energy metabolism and cerebral vaso-dilation are dependent on adequate micronutrient status. This study investigated whether supplementation with ascending doses of multi-vitamin/minerals could modulate the metabolic and cerebral blood-flow consequences of performing cognitive tasks that varied in difficulty.MethodsIn this randomised, double-blind, placebo-controlled, parallel-groups study 97 healthy females (25–49 y), who were not selected on the basis of any nutritional parameters, received either placebo or one of two doses of multivitamins/minerals. Cerebral blood-flow (CBF) parameters in the frontal cortex, and total energy expenditure (TotalEnergy), carbohydrate and fat oxidation (CarbOxi/FatOxi), were measured during 5 tasks of graded cognitive difficulty and a control task (5 min per task) using Near-infrared spectroscopy (NIRS) and Indirect calorimetry of exhaled pulmonary gas (ICa) respectively. Assessments took place 60 min after the first dose and following eight weeks supplementation.ResultsDuring task performance supplementation with the first dose of micronutrients led to a dose-dependent increase in TotalEnergy and FatOxi throughout the post-dose assessment period following the higher dose, and increases in the total concentration of haemoglobin, a proxy measure for CBF, during task performance following the lower dose of vitamins/minerals (also containing coenzyme-Q10). Chronic supplementation over 8 weeks led to a dose-dependent increase in TotalEnergy during the task period. There were no interpretable effects on mood or cognitive performance.ConclusionsThese results show that acute supplementation with micronutrients in healthy adults can modulate metabolic parameters and cerebral blood flow during cognitive task performance, and that the metabolic consequences are sustained during chronic supplementation. These findings suggest that both brain function and metabolism are amenable to micronutrient supplementation, even in adults who are assumed to have nutritional status typical of the population.Trial registrationClinicalTrials.gov - NCT02381964.

Behavioural effects of compounds co-consumed in dietary forms of caffeinated plants

Research into the cognitive and mood effects of caffeine in human subjects has highlighted some fairly robust and well-accepted effects. However, the majority of these studies have focused on caffeine in isolation; whilst caffeine is normally consumed in the form of plant-derived products and extracts that invariably contain other potentially bioactive phytochemicals. The aim of the present review is to consider the possible mechanisms of action of co-occurring phytochemicals, and any epidemiological evidence suggesting that they contribute to potential health benefits ascribed to caffeine. Intervention studies to date that have been conducted to explore the effects on brain function of the non-caffeine components in caffeine-bearing plants (coffee, tea, cocoa, guaraná), either alone or in combination with caffeine, will also be summarised. Research is beginning to accumulate showing independent effects for several of the phytochemicals that co-occur with caffeine, and/or a modulation of the effects of caffeine when it is co-consumed with these naturally concomitant phytochemicals. The present review highlights that more research aimed at understanding the effects of these compounds is needed and, more importantly, the synergistic relationship that they may have with caffeine.

The Acute Effects of Caffeinated Black Coffee on Cognition and Mood in Healthy Young and Older Adults

Cognitive and mood benefits of coffee are often attributed to caffeine. However, emerging evidence indicates behavioural effects of non-caffeine components within coffee, suggesting the potential for direct or synergistic effects of these compounds when consumed with caffeine in regular brewed coffee. The current randomised, placebo-controlled, double-blind, counterbalanced-crossover study compared the effects of regular coffee, decaffeinated coffee, and placebo on measures of cognition and mood. Age and sex effects were explored by comparing responses of older (61–80 years, N = 30) and young (20–34 years, N = 29) males and females. Computerised measures of episodic memory, working memory, attention, and subjective state were completed at baseline and 30 min post-drink. Regular coffee produced the expected effects of decreased reaction time and increased alertness when compared to placebo. When compared to decaffeinated coffee, increased digit vigilance accuracy and decreased tiredness and headache ratings were observed. Decaffeinated coffee also increased alertness when compared to placebo. Higher jittery ratings following regular coffee in young females and older males represented the only interaction of sex and age with treatment. These findings suggest behavioural activity of coffee beyond its caffeine content, raising issues with the use of decaffeinated coffee as a placebo and highlighting the need for further research into its psychoactive effects.

Acute Post-Prandial Cognitive Effects of Brown Seaweed Extract in Humans

(Poly)phenols and, specifically, phlorotannins present in brown seaweeds have previously been shown to inhibit α-amylase and α-glucosidase, key enzymes involved in the breakdown and intestinal absorption of carbohydrates. Related to this are observations of modulation of post-prandial glycemic response in mice and increased insulin sensitivity in humans when supplemented with seaweed extract. However, no studies to date have explored the effect of seaweed extract on cognition. The current randomized, placebo-controlled, double-blind, parallel groups study examined the impact of a brown seaweed extract on cognitive function post-prandially in 60 healthy adults (N = 30 per group). Computerized measures of episodic memory, attention and subjective state were completed at baseline and 5 times at 40 min intervals over a 3 h period following lunch, with either seaweed or placebo consumed 30 min prior to lunch. Analysis was conducted with linear mixed models controlling for baseline. Seaweed led to significant improvements to accuracy on digit vigilance (p = 0.035) and choice reaction time (p = 0.043) tasks. These findings provide the first evidence for modulation of cognition with seaweed extract. In order to explore the mechanism underlying these effects, future research should examine effects on cognition in parallel with blood glucose and insulin responses.

Modulation of cerebral blood flow parameters in humans following consumption of nitrate-rich beetroot juice

Nitrate, abundant in beetroot, has been shown to reduce blood pressure and the oxygen cost of sub-maximal exercise; improve endothelial function and modulate regional perfusion in the brain. In this randomised, placebo-controlled, double-blind, crossover study, 16 physically active healthy young adult males received either 450 ml of beetroot juice (∼5.5 mmol nitrate) or a fruit flavoured placebo drink. Following a 90-min absorption period participants performed Stroop and Rapid Visual Information Processing tasks (9-min each) at rest, and during cycling at 50% and 70% VO2max and finally following exercise. Pre-frontal cerebral haemodynamics, as indexed by concentration changes in oxygenated and deoxygenated haemoglobin, were assessed throughout using Near Infrared Spectroscopy. Dietary nitrate modulated the haemodynamic response to task performance/exercise, with a significant interaction effect revealing lower cerebral deoxygenated haemoglobin relative to placebo during each task within each of the four post-intervention assessments. Dietary nitrate also significantly reduced systolic blood pressure post-exercise and time to limit of tolerance during 90% VO2max was significantly increased. Cognitive performance was unaffected. These data support previous reports of modulation of blood pressure and lowered deoxygenated haemoglobin in muscle following dietary nitrate and demonstrate that this effect on deoxygenated haemoglobin extends to the frontal cerebral cortex. Taken together these findings suggest a decrease in oxygen extraction during mental and physical performance with no resultant detrimental effects on cognitive performance and a positive effect on physical performance, suggesting a decrease in oxygen cost.