The study investigated whether sixteen weeks of oral Hericium erinaceus affected cognitive function, measured on a scale based on the Revised Hasegawa Dementia Scale.

Participants were randomised to Hericium erinaceus tablets or placebo for sixteen weeks under double-blind conditions, with cognitive assessment at four-weekly intervals and a further four weeks of observation after intake ceased.

The authors reported that participants receiving Hericium erinaceus scored significantly higher on the cognitive function scale than placebo at weeks 8, 12 and 16, and that scores rose with duration of intake. Scores declined significantly in the four weeks after intake stopped. Laboratory testing indicated no adverse effect attributable to the intervention.

A small sample of fifteen participants per arm drawn from a single national population. Participants had diagnosed mild cognitive impairment, so the findings do not describe healthy adults. A single cognitive instrument was used, with no biomarker or imaging endpoints, and the difference did not persist once supplementation stopped.

The study investigated both the acute single-dose and the 28-day effects of Hericium erinaceus on cognitive performance, subjective stress and mood in healthy, cognitively unimpaired adults.

Participants were randomised in a double-blind, parallel-groups design to 1.8 g per day of Hericium erinaceus or placebo for 28 days. Cognitive performance was assessed at intervals after the first dose and again at day 29, using the Stroop task, word recall, a global cognition composite, the Perceived Stress Scale and Visual Analogue Mood Scales.

The authors reported significantly faster Stroop task performance 60 minutes after a single dose. No statistically significant difference was observed on the global cognitive composite or on most individual tasks, and reduced accuracy on immediate word recall was observed acutely. At 28 days no statistically significant differences were observed on the stress or mood scales.

An explicitly designated pilot study with a small sample, and the authors state the findings should be interpreted with caution. Multiple outcomes assessed at several timepoints raise the possibility of chance findings, and one memory measure moved in an unfavourable direction. The population was young and healthy over a short 28-day period.

The study investigated the stress-relieving effects of a standardised ashwagandha extract in adults reporting high stress, and examined the hormonal changes accompanying them.

Sixty stressed but otherwise healthy adults were randomised to 240 mg of a standardised extract once daily or matched placebo for sixty days under double-blind conditions. Outcomes were the Hamilton Anxiety Rating Scale and the DASS-21, alongside morning cortisol, DHEA-S and testosterone. The trial was prospectively registered.

All sixty participants completed the trial with no adverse events recorded. Participants receiving ashwagandha showed a statistically significant reduction in Hamilton Anxiety Rating Scale scores relative to placebo, and significantly greater reductions in morning cortisol. The reduction on the DASS-21 did not reach statistical significance.

A small single-site sample over sixty days. The primary between-group anxiety difference was marginal while a second validated scale returned a null result. The study was funded by the manufacturer of the extract tested, and much of the wider literature on this ingredient originates from a narrow set of research groups.

The study investigated whether eight weeks of a standardised Withania somnifera extract, added to existing stable medication, altered cognitive performance, alongside mood stability and tolerability.

Participants maintained on stable medication were randomised in a double-blind fashion to 500 mg per day of the extract or placebo for eight weeks. A battery covering working memory, attention and social cognition was administered with mood and anxiety rating scales. Primary funding came from an independent research foundation.

The authors reported a statistically significant advantage for the extract on three of the cognitive tasks assessed, with a medium effect size on one. No statistically significant differences were observed on the remaining cognitive measures, and mood and anxiety scores remained stable in both groups. Adverse events were described as minor.

Only three of a large number of cognitive comparisons reached significance, so chance findings from multiple testing cannot be excluded. Attrition was uneven between groups, the sample was small, and participants were a medicated clinical population rather than healthy adults. Study material was supplied by the extract manufacturer.

The study investigated whether Korean Red Ginseng extract reduces fatigue in healthy adults over three weeks, alongside a full safety assessment.

Forty-six healthy adults were randomised to Korean Red Ginseng extract or matched placebo for three weeks under double-blind conditions. Fatigue was assessed by visual analogue scale, with plasma lactic acid and cortisol as objective markers, and safety monitored through adverse events, urinalysis, haematology and blood biochemistry.

The authors reported significantly lower fatigue scores in participants receiving Korean Red Ginseng than placebo. No statistically significant difference was observed between groups for plasma cortisol or lactic acid, so the effect was seen in self-rated fatigue rather than in those blood markers. Safety measures were comparable to placebo.

A small sample over a short three-week period. The benefit was confined to a self-reported measure while both objective fatigue markers returned null results, so results should be interpreted cautiously. The study was published in a journal closely associated with the ginseng industry.

The study set out to determine whether a standardised Panax ginseng extract was superior to placebo for fatigue, with quality of life, mood and symptom burden as secondary endpoints.

Patients reporting moderate or greater fatigue were randomised to 400 mg of Panax ginseng extract twice daily or matched placebo for 28 days. The primary endpoint was change in a validated fatigue subscale, with quality of life, anxiety, depression and functional scores assessed as secondary endpoints.

No statistically significant difference was observed between groups on the primary fatigue endpoint. Both groups improved significantly from baseline, indicating a substantial placebo and regression-to-the-mean component. Secondary outcomes covering quality of life, mood and function were also not significantly different between groups.

Conducted in a single clinical population over 28 days, so the null result does not describe healthy adults, other doses or longer exposures. Fatigue was measured by self-report instruments sensitive to expectancy effects, and the marked improvement in the placebo group limits the sensitivity of the comparison.

The study investigated whether ninety days of a standardised Bacopa monnieri extract altered cognitive performance in healthy adults relative to placebo, using a validated computerised battery.

Healthy adults were randomised in a double-blind, placebo-controlled independent group design and received the extract or matched placebo daily for ninety days. Cognitive assessment was conducted at baseline and after the treatment period using the Cognitive Drug Research computerised system.

The authors reported significantly improved performance on the working memory factor, specifically spatial working memory accuracy, in participants receiving the extract. A reduction in false-positive responses on a rapid visual information processing task was also reported. The authors noted that the effective dosage range and the effects of longer administration remain to be established.

Substantial attrition, with 62 of 107 recruited participants completing, which reduces statistical power and raises the possibility of differential dropout. Effects were confined to a subset of measures within a broad battery, so multiple-comparison inflation cannot be excluded. A single proprietary extract at one dose was tested in healthy volunteers.

The study set out to assess the effects of twelve weeks of Bacopa monnieri extract on learning, memory, information processing and anxiety in healthy adults, noting that inconsistent results in the existing literature may relate to methodological differences.

Seventy-two healthy adults were randomised in a double-blind, placebo-controlled parallel-group design to 450 mg per day of the extract or matched placebo for twelve weeks. Outcome measures covered verbal learning and memory, inspection time, attention and interference, alongside state and trait anxiety.

No statistically significant difference was observed between the extract and placebo groups on any of the cognitive measures assessed. The authors reported a non-significant trend towards lower state anxiety, and framed the overall findings as challenging earlier reports of cognitive and anti-anxiety effects.

With 72 participants across two groups the trial may have been underpowered to detect small effects, so a null result does not establish the absence of an effect. A single dose over a single twelve-week period was tested in healthy, non-impaired adults, which may limit sensitivity to change.

The study investigated the effects of spray-dried red and black maca extracts on self-reported mood, energy and health-related quality of life, alongside blood glucose, blood pressure and haemoglobin, with acceptability and safety as secondary outcomes.

Participants were randomised in a double-blind, placebo-controlled design to 3 g per day of placebo, red maca extract or black maca extract for twelve weeks. Outcomes were assessed by questionnaire alongside blood glucose, blood pressure and haemoglobin measurement, with adverse effects self-recorded throughout.

The authors reported that participants receiving red or black maca recorded higher mood, energy and health status scores than placebo, with the larger differences reported for red maca. Both extracts were well tolerated with no serious adverse effects recorded.

Mood and energy outcomes were self-reported questionnaire measures rather than objective performance tests. The published abstract contains an internal inconsistency between the stated participant total and the reported group allocations. The cohort comprised Peruvian lowland and highland residents, and cultivars differ considerably in composition, which limits comparison with other trials.

The study investigated whether fourteen days of maca extract supplementation altered endurance cycling performance in trained male cyclists compared with placebo.

Eight experienced male cyclists completed 40 km cycling time trials before and after each of two fourteen-day supplementation periods in a randomised, double-blind crossover design with a washout of at least one week. Time-trial performance was the principal physiological outcome.

Participants receiving maca improved their 40 km time-trial performance relative to their own baseline. However, no statistically significant difference was observed between the maca and placebo conditions after supplementation, so the improvement did not exceed that seen with placebo.

A very small sample of eight participants, described by the authors as a pilot investigation, so it is underpowered and the null between-group result cannot be treated as evidence of no effect. Two authors were affiliated with the company supplying the extract, and the cultivar used was not specified.