When most people think of rosemary, it typically brings to mind something delicious to eat, but not necessarily its mind altering effects. That just goes to show that we still have a lot to learn about the therapeutic effects of rosemary and other plants containing “essential oils.” Researchers publishing in Therapeutic Advances in Psychopharmacology, have shown for the first time that blood levels of a component found in rosemary oil correlate with improved cognitive performance.
Rosemary (Rosmarinus officinalis) is one of many historically “medicinal” plants that contain essential oils. How such plants affect our behaviour is still unclear. Mark Moss and Lorraine Oliver, working at the Brain, Performance and Nutrition Research Centre at Northumbria University in the UK, designed an experiment to investigate the pharmacological effects of 1,8-cineole, one of rosemary’s main chemical components.
Cognitive performance and mood were tested in 20 subjects, who were exposed to different levels of the rosemary aroma. Using blood samples to detect the amount of 1,8-cineole subjects had actually absorbed, the researchers used speed and accuracy tests, and mood assessments to judge the rosemary oil’s affects.
For the first time in human subjects, the results demonstrate that the concentration of 1,8-cineole in the blood is related to an individual’s cognitive performance – with higher concentrations resulting in improved performance. Both speed and accuracy were improved, suggesting that its not just a speed–accuracy trade off.
The chemical also had an effect on mood, although much less pronounced. However, this was a negative correlation between changes in contentment levels and blood levels of 1,8-cineole. What makes this even more interesting is that it suggests that compounds given off by the rosemary essential oil affect mood and cognitive performance through different neurochemical pathways. The oil did not appear to improve attention or alertness.
“Only contentedness possessed a significant relationship with 1,8-cineole levels, and interestingly to some of the cognitive performance outcomes, leading to the intriguing proposal that positive mood can improve performance whereas aroused mood cannot,” said Moss, in a press release.
Terpenes like 1,8-cineole can enter the blood stream via the nasal or lung mucosa. As small, fat-soluble organic molecules, terpenes can easily cross the blood–brain barrier. Volatile 1,8-cineole is found in many aromatic plants, including eucalyptus, bay, wormwood and sage in addition to rosemary, and has already been the subject of a number of studies, including research that suggests it inhibits acetylcholinesterase (AChE) and butyrylcholinesterase enzymes, important in brain and central nervous system neurochemistry: rosemary components may prevent the breakdown of the neurotransmitter acetylcholine.