In this small study, 22 healthy individuals between the ages of 20 and 50 drank a cup of rosemary tea (a simple brew of 5 grams of dried rosemary in water) every day for 10 days. Before and after the experiment, researchers ran blood tests to measure key markers of participants’ stress levels and immune response.
While the immunity markers stayed relatively consistent after the daily tea, researchers did find a significant increase in the concentration of one protein: brain-derived neurotrophic factor (BDNF). BDNF is an essential molecule for brain health. Essentially, it helps our noggins grow new neurons and synapses while protecting the ones we already have. BDNF seems to help shield our brain’s neurons from stress-induced damage, and it’s often excreted during bouts of exercise. Normal levels (i.e., not low) of BDNF are considered a biomarker for a healthy mood and mental well-being.
Since BDNF levels increased following the intervention, researchers believe that rosemary might help promote a positive mood and ease everyday stress and anxiousness.* They also found that participants experienced a slight decrease in cortisol levels following their teatime, another signal of a healthy stress response.*
This was only one small trial, and there was no control group (so you can’t rule out the placebo effect), but the results track with existing research on rosemary. Previous studies have found that the herb can help promote calm and improve sleep quality in college students and have a mood-boosting effect on mice.* Supplementing with rosemary led to an increase in self-reported focus, enthusiasm, and outlook in another clinical study, and there’s also good reason to think the herb can help promote memory and cognitive function.*
In short, consuming rosemary seems to be one (delicious) botanical approach to supporting mood and overall brain health.*