The authors of the randomised, placebo-controlled, parallel group study from the United Kingdom assessed the effects of 90 days of a proprietary multi-ingredient herbal supplement, containing nine individual ingredients (Bacopa monnieri, gotu kola leaf, turmeric whole powder, full spectrum reishi, rosemary, cardamom, holy basil, turmeric extract, green tea, and seagreens), in a group of healthy adults, aged 55–75 years.
The authors hypothesise that the positive results could be attributed to a potential interaction with the dopaminergic neurotransmitter system through the gut microbiome.
However, as the authors note, herbal products are seldom consumed in isolation and yet much less research has investigated the effects of combinations of herbal compounds, which is a concern as the interaction between compounds could be anticipated to exert effects not seen when supplemented alone.
The researchers emphasise the importance of turning to multi-herbal supplementation due to its potential to influence the intricate web of pathways that underlie cognitive activities.
The amalgamation of various herbs, encompassing terpenes, phenolic compounds, micro- and macro-nutrients, and polysaccharides, is suggested to be especially effective in enhancing cognitive function.
These phytochemical groups individually target key mechanisms that directly and indirectly support cognitive function, and the authors of the study suggest that when combined, they offer a more comprehensive approach to boosting cognition.
For instance, terpenes, such as those found in Waterhyssop (Bacopa monnieri), have been shown to enhance cognitive performance and memory, particularly in older populations with mild cognitive impairment.
Supplementation with Seagreens, rich in macro- and micro-nutrients, has been found to support brain development, neurone firing, and neurotransmitter regulation, potentially due to its iodine and calcium and potassium levels.
Polysaccharides from herbal compounds like Reishi and Seagreens, which feed the gut microbiota in the mammalian large intestine, have been found to potentially impact brain function by promoting gut-brain axis communication, with potential mechanisms underpinning this gut-brain-axis connection including communication via the Vagus nerve, the immune system, the HPA axis, regulation of neurotransmitter metabolism and synthesis and systemic inflammation.
Despite evidence for the benefits of these herbal compounds, the effects of multi-ingredient herbal supplements remain limited.
Therefore, the authors of the new study suggest that combining herbs with various phytochemical groups, such as terpenes, phenolics, micro- and macro-nutrients, and polysaccharides, can have a more comprehensive impact on cognitive function due to their diverse mechanisms of action in the brain.
Male and female participants (N = 128) aged between 55–75 years completed lab-based cognitive assessments, and provided stool and urine samples, at baseline and then following 90 days of multi-ingredient herb, or placebo, supplementation.
Positive effects were all focused on speed of cognitive task performance, with an additional improvement in the false alarm rate on the rapid visual information processing task.
The improvements were found to coincide with an increased presence of tyrosine in the urinary metabolome, and the researchers suggest this may implicate the role of dopamine in these processing and/or motor speed increases.
The multi-ingredient herbal supplementation was also found to significantly reduce levels of three bacterial species in the gut microbiome and one of these, Sutterella, coincides with lower levels of constipation.
Surprisingly, memory deficits were observed in response to 90 days of multi-ingredient herbal supplement supplementation.
However, the authors note that the COVID-19 pandemic, which disrupted the study, could also have influenced the results, given its known impact on cognitive function.
They add that the unequal randomisation of treatment groups before and after the pandemic makes it challenging to determine its exact impact.
Journal: Frontiers in Nutrition
Volume 10 - 2023, doi: 10.3389/fnut.2023.1257516
“Chronic supplementation of a multi-ingredient herbal supplement increases speed of cognitive task performance alongside changes in the urinary metabolism of dopamine and the gut microbiome in cognitively intact older adults experiencing subjective memory decline: a randomized, placebo-controlled, parallel groups investigation"
Authors: E. Wightman, et al.