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A Half Teaspoon of Dried Rosemary May Improve Cognitive Function

In Hamlet, Act 4, Scene 5, 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, awakens the mind…” After all, “plants can be considered as chemical factories that manufacture all sorts of compounds that could have neuroprotective benefits”. So, let’s cut down on processed foods and eat a lot of phytonutrient-rich whole plant foods, including, perhaps, a variety of herbs. Even the smell of certain herbs may affect how our brain works. Unfortunately, as I discuss in my video Benefits of Rosemary for Brain Function, I’ve found much of the aromatherapy literature scientifically unsatisfying. There are studies offering subjective impressions, for example, but while sniffing an herbal sachet is indeed “easy, inexpensive, and safe,” is it effective? The researchers didn’t even compare test scores.

However, even when there was a control group, such as one study where researchers had people perform a battery of tests in a room that smelled like rosemary, lavender, or nothing, and even when the researchers did compare test results, the lavender appeared to slow down the subjects and impair their performance, whereas the rosemary group seemed to do better. Perhaps that was just because of the mood effects, though, as I show at 1:36 in my video. Maybe the rosemary group did better simply because the aroma pepped them up in some way—and not necessarily in a good way, as perhaps the rosemary was somehow overstimulating in some circumstances?

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, as well as associate them with objective changes in stress hormone levels, as you can see at 2:05 in my video, but is that all simply because pleasant smells improve people’s moods? For instance, if you created a synthetic rosemary fragrance with a bunch of chemicals that had nothing to do with the rosemary plant, would it have the same effect? We didn’t know…until now.

Aromatic herbs do have volatile compounds that theoretically could enter the blood stream by way of the lining of the nose or lungs and then potentially cross into the brain and have direct effects. A 2012 study was the first to put it to the test. Researchers had people do math in a cubicle infused with rosemary aroma. The subjects got that same boost in performance, but for the first time, the researchers showed that their improvement correlated with the amount of a rosemary compound that made it into their bloodstream just from being in the same room. So, not only did this show that it gets absorbed, but that such natural aromatic plant compounds may have a direct effect on changes in brain function.

If that’s what just smelling it can do, what about eating rosemary? We have studies on alertness, 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 of 75, were given two cups of tomato juice, with either nothing, a half teaspoon of powdered rosemary, which is what one might use in a typical recipe, a full teaspoon, two teaspoons, more than a tablespoon of rosemary powder, or placebo pills to go even further to eliminate any placebo effects.

“Speed of memory is a potentially useful predictor of cognitive function during aging,” and, as you can see at 4:08 in my video, researchers found that the lowest dose had a beneficial effect, accelerating the subjects’ processing speed, but the highest dose impaired their processing speed, perhaps because the half-teaspoon dose improved alertness, while the four-teaspoon dose decreased alertness. So, “rosemary powder at the dose nearest normal culinary consumption demonstrated positive effects on speed of memory…” The implicit take-home message is more isn’t necessarily better. Don’t take high-dose herbal supplements, extracts, or 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, but that doesn’t mean you can eat the whole rosemary bush. In one study, an unlucky guy swallowed a rosemary twig that punctured through the stomach into his liver, causing an abscess from which two cups of pus and a two-inch twig were removed. So, explore herbs and spices in your cooking. Branch out—just leave the branches out.

That twig is like a plant-based equivalent of Migrating Fish Bones!

Interested in more on aromatherapy? See:

For more on spicing up your life, check out:

And, learn more about improving cognition and preventing age-related cognitive decline in:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:



Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

30 responses to “A Half Teaspoon of Dried Rosemary May Improve Cognitive Function

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    1. Tom,

      I read the link but I will tell you that I would have just skipped right over it because they use sentences like, “May decrease stress” versus “May decrease cortisol.”

      Dr. Greger’s study where the half-teaspoon dose improved alertness, while the four-teaspoon dose decreased alertness is so useful.

      I have been monitoring my brain and it still has such big gaps.

      I forget things are so basic. I still have enough brainpower to say, “Uh oh” when I recognize how bad it is that I forget the things I forget. But I am fighting back by continuing to try to learn things and I am learning and forgetting at the same time.

      I am not learning enough to be a Flowers for Algernon type of increase followed by not knowing whether 10 is bigger than 8. That isn’t what I messed up but it has been things that basic and it happens often enough that I know that I am in a war for my brain.

      I might even put some herbs in little bowls around the house. Harder to overdo that way.

      1. Wow. I am impressed that you kn ow the Flowers for Algernon story.

        I read it years ago. It was turned into a film at one point if memory serves.

        The thing that jumped out at me from that link was ‘Ingestion of large quantities of rosemary may result in ………. kidney damage.’

      2. Deb,
        I have been listening Dr. Caroline Leaf, who knows her brain research! PhD in Communication Pathology. She offers exercises to help your brain.

        Say everyday….I’ve decided to make more glial cells…..
        These are the cells that help us retrieve memories, our bodies will do what we believe.

  1. Thank you Dr. Michael Greger, I am learning to use more spices when I cook…
    Sorry, I follow your blog better than the videos which appear to be too time consuming for me. However, if I had time, I would watch them. I do like both formats. Kind regards.

    1. Laughing.

      I have a theory about vows because the grooms often mess up a line and that line is often the key one for them.

      I watched one who was highly money-oriented mess up on the richer or poorer and one who is youthful-oriented messed up on “death do us part” I can’t remember the other examples, but they always messed up perfectly at the right time.

  2. sorry i’m a little confused so the recommendation is to eat half a tsp dried rosemary every day but if more than half a tsp per day is consumed it’s detrimental and has the opposite effect?

    1. The recommendation is to use spices and herbs in your everyday cooking in culinary amounts. (whole rosemary can be tied in cheesecloth and used in soups and stews) Rosemary was also tested as aromatherapy when subjects did math problems in a cubicle infused with rosemary scent.

  3. If you’re interested in improving or preserving memory function (and who amongst us isn’t?) I just read a wonderful book written by Dr. Ayesha Sherzai and Dr. Dean Sherzai called “The Alzheimer’s Solution”. Their first suggestion is eating a WFPB diet…DR. G would approve! The book is all about the power of lifestyle, not drugs.

    1. I saw them interviewed on the Rich Roll Podcast. It was excellent. AFAIK Dr. Dean Ornish is conducting clinical trials on reversing Alzheimer’s with a WFPB diet and other lifestyle modifications right now.

      1. I have been interested particularly after seeing the details of what they will be looking at.

        1) The primary endpoint measure is cognitive function testing.

        2) Changes in hippocampal volume at Dr. Howard Rosen’s lab at UCSF;
        3) telomere length at Dr. Elizabeth Blackburn’s lab at UCSF
        4) changes in the microbiome at Dr. Rob Knight’s lab at UCSD
        5) inflammatory biomarkers at UCSF;
        6) changes in gene expression and proteomics at Dr. David Sinclair’s lab at Harvard.

        Can I use the pun that it is a no-brainer that many of those will probably show good results? But if the hippocampus volume fails, it will be a less-brainer. But if the primary endpoint is met, then, even if the hippocampus volume fails, it might be a none-the-less brainer.

        40 weeks.

        I just looked and I think it is still accepting patients, so I am not sure it really has started yet.

        I look now and then.

        I also am not 100%

          1. Fumbles, also, exercise and sleep are the two lifestyle factors that impact hippocampus size and cognitive function.


            Max Cynader (leading brain researcher) talk on maintaining brain health.

            A couple of months ago I saw an interview of Dr Greger by Plant based news where they asked him about Dr Ornish’ research. I recall Dr Greger saying it was disappointing ie a wash, but I believe that had to do with the ‘reversing ‘ aspect. I have been trying to find that interview to post. Certainly from a preventative and a supportive viewpoint, a whole food balanced diet is one of the best things we can do for ourselves.

    1. Marilyn, I also grow rosemary, sage, and even some thyme, in my small garden.
      And, yes, you can’t beat the taste of fresh leaves picked right off the plant!

    2. Marilyn,

      I was just pondering Sage last night at Whole Foods.

      The concept of sage advice is something I will look into where it came from.

      My history with it is more like what YR said of a smudge burning – though not for aura cleansing. I think in college people did it to cover up pot smell and in California we used to do Native American sweat lodges and all sorts of fun things. I liked float tanks, but I always liked the smell of sage.

      I did a lot of the sound and light and smell experimental things. That all probably started for me in college, too. I had a class where the teacher would assign us things and I still find it all useful.

      I used to be more skeptical and maybe still am about the wider “healing” culture but today, I ended up watching grotesque video after grotesque video where homeopathy healed gangrene and their methodology still bothers me. But they have some pretty amazing results.

      I laugh because they give things and say, “She was indifferent to her husband” so we give this and THAT logic is not comforting to me.

      But when I back away from their logic and see things like sulfur and start thinking about the vegetables with sulfur and I see silica and think about how much the silica water helped my brain, I want someone other than the homeopathic peddlers to do the logic with studies rather than case studies.

      But they still do get results.

      I just could never give my cousin arsenic even with a homeopathic name even though I can look at videos of gangrene getting healed and say that they seem to have good results.

      So does infrared and so does PEMF and other things.

      Apparently, only the medical doctors can’t seem to figure out anything to give to avoid amputation is my sarcastic comment and that comes because I just watched seriously grotesque videos and found so many things.

      The homeopathic doctors – some just give one thing and some 10 things and I don’t understand the logic enough to do it with my cousin. But I am still looking to see if any of it is safe for diabetics with gangrene.

      I have good feelings about the infrared and PEMF and amino acids.

      It should be a medical person giving him things to try.

      They don’t even try any of the things and that does frustrate me.

      Amputation should be last.

      1. Homeopathy can work is what conclusion I come to. But the way they figure out which one to use is a list of things like:

        Uses a lot of covers because they are cold and likes to be alone and all sorts of symptoms.

        I want them to rephrase everything by the mechanism.

        Tell me that they are cold from poor circulation and don’t have a sexual response due to low nitric oxide or anything other than what they do.

  4. There are many books about aromatherapy.
    I wonder if using dozens different plant oils is of any help
    Sometimes i burn the nice smelling commercial wooden sticks just for fun
    I use just dried herbs like mint . rosemary …

  5. PEMF also doubles the effectiveness of fungal infection treatments and lowers the virulence of viral infections.

    Dr Pawluk speculated that it might help with COVID by the same mechanisms it helps with other viral infections but they made him take it down.

  6. Dear Dr Greger! What is your opinion on essential oil rosemary? It is highly sourced with the upmost distillation standards. Please advise!
    Beneita Flemmer

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