The Acute and Chronic Cognitive and Cerebral Blood Flow Effects of a Sideritis scardica (Greek Mountain Tea) Extract: A Double Blind, Randomized, Placebo Controlled, Parallel Groups Study in Healthy Humans

Abstract

Background: The presence of polyphenols such as hydroxy-cinnamic acids and flavonoids in Sideritis scardica (Greek mountain tea) are likely responsible for the cognitive and mood effects of its consumption and this could be underpinned by the ability of such polyphenols to prevent monoamine neurotransmitter reuptake and to increase cerebral blood flow (CBF). Objective: The current study extends the small amount of Sideritis scardica literature in humans by assessing both cognitive and mood outcomes in a sample of older adults, as well as blood pressure (BP) and CBF, in a subsample, utilizing near-infrared spectroscopy (NIRS). Design: This randomized, double-blind, placebo-controlled, parallel groups trial randomized N = 155, 50–70-year-old male and female participants who were assessed for the cognitive (N = 140), mood (N = 142), BP (N = 133) and CBF (N = 57) effects of two doses of Greek mountain tea (475 and 950 mg) as well as an active control of 240 mg Ginkgo biloba, and a placebo control, following acute consumption (Day 1) and following a month-long consumption period (Day 28). Results: Relative to the placebo control, 950 mg Greek mountain tea evinced significantly fewer false alarms on the Rapid Visual Information Processing (RVIP) task on Day 28 and significantly reduced state anxiety following 28 days consumption (relative also to the active, Ginkgo control). This higher dose of Greek mountain tea also attenuated a reduction in accuracy on the picture recognition task, on Day 1 and Day 28, relative to Ginkgo and both doses of Greek mountain tea trended towards significantly faster speed of attention on both days, relative to Ginkgo. Both doses of Greek mountain tea, relative to placebo, increased oxygenated haemoglobin (HbO) and oxygen saturation (Ox%) in the prefrontal cortex during completion of cognitively demanding tasks on Day 1. The higher dose also evinced greater levels of total (THb) and deoxygenated (Hb) haemoglobin on Day 1 but no additional effects were seen on CBF on Day 28 following either dose of Greek mountain tea. Ginkgo biloba led to lower levels of Ox% and higher levels of Hb on Day 1 and lower levels of both HbO and THb on Day 28. Conclusions: The significantly improved cognitive performance following Greek mountain tea on Day 1 could be due to significant modulation of the CBF response. However, these improvements on Day 28 are more likely to be due to the reductions in state anxiety and, taken together, suggests that the former mechanism is more likely to facilitate acute cognitive effects and the latter more likely to underpin more prolonged cognitive improvements.

The Effect of (Poly)phenol-Rich Interventions on Cognitive Functions and Neuroprotective Measures in Healthy Aging Adults: A Systematic Review and Meta-Analysis

“…Fifteen studies [26][27][28][29][30][31][35][36][37][40][41][42][43][44][45] met the inclusion criteria and were included in the current systematic review. The studies examined the effects of (poly)phenol-rich supplementation intake on cognitive functions and/or brain-related parameters (e.g., neuroimaging, neuroplasticity, CBF, etc).…”

“…Eight papers [26,27,35,36,40,41,43,44] examined only the effect of rich-(poly)phenol supplementation on different cognitive functions such as visual attention, working memory, reaction time, executive functioning, and learning abilities. Five studies [28,29,31,37,42] examined the effect of rich-(poly)phenol supplementation on cognitive function as well as a variety of brain-related parameters such as brain perfusion, cerebral blood flow, cerebral hemodynamics, hippocampal functional connectivity, neuroplasticity, neuroinflammation, and other brain-related parameters. Two studies [30,45] only examined the change in cerebral blood flow parameters following rich-(poly)phenol supplementation without cognitive function measurements.…”

“…Two studies [30,45] only examined the change in cerebral blood flow parameters following rich-(poly)phenol supplementation without cognitive function measurements. Concerning the acute (up to 2 h) and chronic effects of (poly)phenol-rich supplementation on the abovementioned functions, twelve studies investigated the chronic effect [26,27,29,31,35,36,[40][41][42][43][44][45], two studies investigated only the acute effect [30,37], and only one study [28] investigated both acute and chronic effect of (poly)phenol-rich supplementation on cognitive and brain functions.…”

“…These (poly)phenol compounds (i.e., flavones, flavonols, isoflavones, flavanones/flavanonols, flavanols, and anthocyanidins) are present in high amounts in fruits, vegetables, and natural products such as parsley, celery, onions, leeks, broccoli, soy, oregano herbs, green tea, red wine, citrus fruit, berry fruits, and dark chocolate [20,21]. Although research has historically focused on antioxidant properties [22][23][24][25], recent data from randomized placebo-controlled trials suggest (poly)phenols may also modulate neurological disorders, cerebral hypoperfusion, and neuroinflammation while simultaneously enhancing memory, learning, and cognitive performances in old-aged adults [19,[26][27][28][29][30][31][32][33][34]. Mastroiacovo et al [26] demonstrated a daily consumption of 250 mL Cocoa drinks, with a high flavanol content (993 mg), for 8 weeks has the potential to improve psychomotor performance, verbal fluency performance, as well as the overall cognitive performance (i.e., z-score).…”

“…Whyte et al [27] indicated that 3 months of daily supplementation with 100 mg purified wild blueberry extract, with a total (poly)phenol of 50 mg, improved both verbal and short-term spatial episodic memory functions. Furthermore, Wightman et al [28] showed that acute supplementation with Greek mountain tea (950 mg) improves accuracy of working and episodic memory, speed of attention, processing of visual information, and cerebral hemodynamics in the prefrontal cortex. Improvements in resting regional cerebral blood flow have also been reported following an acute ingestion of high-flavanol (494 mg) cocoa drink [30] and after daily ingestion of 387 mg anthocyanin-rich blueberry concentrate for 12 weeks [31].…”