Mint Family (Lamiaceae)
In Latin, rosemary means dew of the sea, and its native habitat includes rocky and poor soil conditions by the Mediterranean Sea. Like other aromatic mint family plants, rosemary has long been used to help preserve food, well before research confirmed the antimicrobial properties of these herbs. Interestingly, rosemary was traditionally considered an herb of remembrance to remember a loved one at particular rituals or events, and to improve memory when studying (De la Foret, n.d.). Traditionally, it has also been used to alleviate pain and anxiety, and for its antimicrobial properties, but contemporary research is revealing a range of other benefits of rosemary.
Rosemary can help protect the skin from sun damage when taken orally.
One study found that a combination of rosemary extract enriched in polyphenols and diterpenes and a citrus bioflavonoid extract inhibited ultraviolet (UV) damage on human cells in vitro (outside of a living organism) and in human volunteers taking the extracts orally (Pérez-Sánchez et al., 2014). The effects were stronger with the combination of extracts than with the individual extracts, and also stronger than the sum of the effects of the individual extracts. Significant effects were seen after eight weeks of daily supplementation and were stronger after 12 weeks (Pérez-Sánchez et al., 2014).
In an animal study, rosemary essential oil was found to result in greater wound healing than the rosemary water extract (de Macedo et al., 2020).
In an in vitro study of human melanoma cells; rosemary extract resulted in a dose-dependent reduction of melanoma (skin cancer) cell growth (de Macedo et al. 2020). In a different animal model study, treatment with oral doses of rosemary extract for 15 days resulted in a reduction in number and size of tumours (de Macedo et al., 2020).
Rosemary extract and rosemary essential oil is approved by the European Commission and US Food and Drug Administration for addition to foods to prevent bacteria and extend shelf life (Ribeiro-Santos et al., 2015). An in vitro study has shown that rosemary extract at a concentration of 40ug/ml inhibits growth of herpes simplex virus type 1 and type 2 cells (Al-Megrin et al., 2020).
Rosemary’s warmth can help during early stages of a fever, when feeling cold. A rosemary tea can help soothe a sore throat, and rosemary can also alleviate congestion in the sinuses and lungs through inhalation (De la Foret, 2017).
As a warming, aromatic herb, rosemary can ease stagnant or cold digestion, like some other mint family herbs. Because it has milder energetics than ginger, garlic, and cayenne, it can be used in somewhat larger quantities in food. It has likely been paired with fatty foods to support the liver, which releases bile to help support fat digestion (De la Foret, 2017).
In an animal study, supplementation with rosemary leaf was found to improve diastolic function (when the heart fills up with blood before pumping out to body) and reduce hypertrophy (a response to stress on the heart, often a thickening of the heart muscle) after myocardial infarction/heart attack (Murino Rafacho et al., 2017). It is thought to have done this by improving energy metabolism and decreasing oxidative stress (Murino Rafacho et al., 2017). While research specific to human heart health is lacking, the animal study suggests that rosemary may be useful for human heart health.
There is some evidence that rosemary essential oil can stimulate hair growth.
In a randomised, double-blind study, 86 patients with hair loss were given either a blend of essential oils that included rosemary to apply to the scalp, or given the oil without the essential oils (Hay et al., 1998). Nearly half of the essential oil group had improved hair growth compared to six percent of the control group - however, because it was a blend, the effect could not be attributed solely to rosemary (Hay et al. 1998).
In another study, a topical treatment comprised of 10% rosemary essential oil performed as well as minoxidil, a commercial hair loss treatment, when used for six weeks in an in vivo animal model (Uronnachi, et al., 2022).
Because free radical damage can cause inflammation, and can occur if there’s a deficiency of antioxidants in the body, antioxidants can help to counter chronic inflammation. Inflammation can be associated with pain, so antioxidants that counter free radical damage can modulate inflammation, which may then alleviate pain. In an in vitro study, rosemary extract was found to have good free radical scavenging activity, indicating its antioxidant effects (Al-Megrin et al., 2020).
Some of the most renowned effects of rosemary are on the nervous system, and may start to be felt just by having a whiff of its aroma. It can positively affect mood and memory via its aromatic constituents and its other constituents, and even a small quantity can have an effect.
Rosemary is said to have been eaten by Ancient Greek students to improve their memory; students also wore rosemary garlands when studying for examinations (Nutritional Geography, n.d.). Contemporary research is also generating evidence about rosemary’s impact on memory, although most of the studies have been small and further research is needed to elucidate the potential of rosemary to support cognitive function.
In an animal model study, 90 days of administration of rosemary extract containing carnosic acid, one of its medicinal constituents, was found to have a significant protective effect against cognitive dysfunction that affects learning and memory (Farr et al., 2016).
Pengelly et al. (2012) conducted a randomised, placebo-controlled, double-blinded, study of 28 older adults (mean age of 75) to explore effects of rosemary leaf powder on cognitive performance. The study focused on acute effects, so a pre-dose testing session was done to establish baseline performance for that day, followed immediately by the allocated intervention and assessments at 1, 2.5, 4, and 6 hours post-intervention, using a placebo and four doses of rosemary. It revealed that the lowest dose - 750 mg dose of rosemary leaf - improved speed of memory, whereas the highest dose of 6000mg impaired speed of memory. Other measures had mixed results; ‘continuity of attention’ was significantly impaired (compared to placebo) at 1500mg, 3000mg, and 6000mg; quality of working memory was significantly impaired (compared to placebo) at 750mg, 1500 mg, and 6000mg. However, with both of these measures, the differences were small compared to the baseline performance for the day (Pengelly et al., 2012). This study also demonstrates that more is not always better, and modest amounts of herbs can have big impacts.
Rosemary has been found to alleviate anxiety and depression via inhalation and tea ingestion.
In a study of nursing students by McCaffrey et al. (2009), inhalation of rosemary essential oil and lavender essential oil was found to reduce anxiety during examination - as measured by self assessment and pulse rate changes, but students found lavender to be too relaxing for a test-taking context. Students reported that rosemary inhalation helped with both anxiety and focus and concentration (McCaffrey et al., 2009).
In another study, 22 healthy volunteers were given rosemary tea once a day for ten days to assess plasma levels of anxiety and depression biomarkers; the purpose was to explore effects on biomarkers in healthy individuals before experimenting on people with depression (Achour et al., 2022). This study used 5g of dried rosemary in 100ml boiled water, and various markers were assessed before the rosemary consumption and at the end of the experiment. It found partial support for antianxiety and antidepressant effects, mainly by significantly increasing the plasma level of BDNF (brain derived neurotrophic factor), a factor whose impaired function and expression has been found to be associated with several psychiatric disorders, including major depression (Achour et al., 2022).
As with the learning and memory studies, the sample sizes of these studies were small; further research is needed to glean greater understanding of how rosemary affects mood, the most appropriate dosages and ways of using, and the scope of its treatment potential.
A clinical trial of 81 patients found that dried rosemary leaf consumption (300mg/day) helped alleviate withdrawal syndrome symptoms of opium addiction when compared to the control group (Solhi et al., 2013). Patients were assessed at three, seven, and 14 days after the start of the intervention. Rosemary was found to reduce insomnia and relieve musculoskeletal pain during the four weeks of consumption, with significant results at days 3 and 7 for both sleep duration and clinical opioid withdrawal scale scores (Solhi et al., 2013). This points to potential use for treatment of withdrawal syndrome of addiction to opioids other than opium.
Neuropathic pain is caused by damage to the nervous system - the brain, spinal cord, or peripheral nerves (Cleveland Clinic, n.d.). This type of pain is different from pain that occurs from damage to tissues, often by injury, or chronic pain, for example in arthritic joints. Rosemary has long been used for chronic pain and acute pain from injury, and a recent study suggests it may help alleviate neuropathic pain, too.
In one animal model of sciatic nerve constriction, intraperitoneal (abdominal cavity) administration of rosemary and rosmarinic acid ethanolic extract was administered. It was found to prevent nerve damage and reduce inflammatory markers in the lumbar (lower back) spine area when compared to the control (Ghasemzadeh et al., 2016).
As with many aromatic herbs, it’s best to avoid large (more than culinary) doses of rosemary during pregnancy and breastfeeding. Because rosemary may lower blood glucose, those taking insulin should continue to their blood glucose levels. It may slow blood clotting, so people taking anticoagulant drugs should avoid medicinal doses or taking rosemary supplement (WebMD, n.d.). Some people have skin sensitivity to rosemary.