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.
Highlights
Shepherd’s Tea, Olympus tea or, interchangeably referred to as, Greek mountain tea is a popular naturally un-caffeinated Eastern European beverage derived from Sideritis scardica, a hardy perennial which is renowned for flourishing at high altitude
The primary active constituents of the caffeine-free Greek mountain tea appear to be phenolic acids, principally ferulic acid and chlorogenic acid and the flavone compound apigenin [3], and it is likely the latter which underpins the small number of published psychophysiological effects of
>35 kg/m2 ; high blood pressure; smoking; food allergies or insensitivities; pregnancy; breast feeding; currently taking any medication or dietary supplements which would contraindicate with the study; sleep disturbances and/or taking sleep aid medication; history of neurological, vascular or psychiatric illness; current diagnosis of anxiety or depression; migraines; recent history of alcohol/substance abuse; disorder of the blood; heart disorder/history of vascular illness; respiratory disorder requiring regular medication; Type I or II diabetes; renal disease; hepatic disease; severe disease of the gastrointestinal tract, and any health condition that would prevent the fulfilment of the study requirements
Summary
Shepherd’s Tea, Olympus tea or, interchangeably referred to as, Greek mountain tea is a popular naturally un-caffeinated Eastern European beverage derived from Sideritis scardica (ironwort), a hardy perennial which is renowned for flourishing at high altitude. Sideritis scardica is a triple monoamine (serotonin, noradrenaline and dopamine) reuptake inhibitor in vitro [4] with apigenin individually demonstrating a capacity to interact with monoamine transporters [5] as well as being a ligand for the benzodiazepine receptor This latter effect results in anxiolytic effects in mice during the stressful elevated plus maze task and may underlie the small number of mood improving effects in humans published recently. 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 to the active, Ginkgo control) This higher dose of Greek mountain tea 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. 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
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