Rosemary & the Brain

Even when there is a control group, where researchers had people do a battery of tests in a room that smelled like rosemary, lavender, or nothing, and even when they did compare test results, the lavender appeared to slow them down, impair their performance, whereas the rosemary group seemed to do better. But, maybe that’s just because of the mood effects.

Atsumi T, Tonosaki K. Smelling lavender and rosemary increases free radical scavenging activity and decreases cortisol level in saliva. Psychiatry Res. 2007 Feb 28;150(1):89-96. https://www.ncbi.nlm.nih.gov/pubmed/17291597

McCaffrey R, Thomas DJ, Kinzelman AO. The effects of lavender and rosemary essential oils on test-taking anxiety among graduate nursing students. Holist Nurs Pract. 2009 Mar-Apr;23(2):88-93.

Now, there have been studies that measured people’s brain waves, and were able to correlate the EEG findings with the changes in mood and performance, along with objective changes in stress hormone levels. But is this all just because pleasant smells improve people’s moods? Like, if you created some synthetic rosemary fragrance with a bunch of chemicals that had nothing to do with the rosemary plant, would it still have the same effect?

 

Aromatic herbs do have volatile compounds that theoretically could enter the bloodstream by way of the lining of the nose or lungs, and then potentially cross into the brain, and have direct effects. But, this was the first study to put it to the test. They had people do math in a cubicle infused with rosemary aroma. And so, yes, they got that same boost in performance, but for the first time, showed that how much better they did correlated with the amount of a rosemary compound that made it into their bloodstream, just from being in the room. And so, not only did this show that it gets absorbed, but that such natural aromatic plant compounds may be playing a direct effect on changes in brain function.

 

If that’s just what smelling it can do, what about eating rosemary? We have the studies on alertness and cognition and reduced stress hormone levels inhaling rosemary.

 

However, there were no clinical studies on cognitive performance following ingestion of rosemary, until now. Older adults, average age 75, were given two cups of tomato juice, with either nothing, or a half-teaspoon of powdered rosemary, which is what one might use in a typical recipe, or a full teaspoon, two teaspoons, or over a tablespoon of rosemary powder. And, they even gave them some placebo pills to go with it, to even further eliminate any placebo effects.

 

“Speed of memory is a potentially useful predictor of cognitive function during aging.” And, what they found is that the lowest dose had a beneficial effect, accelerating their processing speed. But, the highest dose impaired their processing speed, maybe because the half-teaspoon dose improved alertness, while the four-teaspoon dose “decreased alertness.” So, “rosemary powder at the dose nearest to normal culinary consumption demonstrated positive effects on speed of memory”—the implicit take-home message being more isn’t necessarily better. Don’t take high-dose herbal supplements, extracts, tinctures; just cooking with spices is sufficient. A conclusion, no doubt, pleasing to the spice company that sponsored the study.

No side effects were reported,

  • Hugel HM. Brain Food for Alzheimer-Free Ageing: Focus on Herbal Medicines. Adv Exp Med Biol. 2015;863:95-116.
  • In Hamlet, act IV, scene V, Ophelia notes that rosemary is “for remembrance,” an idea that goes back at least a few thousand years to the ancient Greeks, who claimed that rosemary “comforts the brain,…sharpens understanding, restores lost memory, [and] awakens the mind.” After all, plants can be considered little “chemical factories” that manufacture all sorts of compounds that could have “neuroprotective benefits.”

 

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