Rosemary is probably a staple in your spice cabinet, up there with parsley, sage, and thyme. But did you know that this aromatic herb in the mint family (botanical name Rosmarinus officinalis) is also sold in capsules and tinctures, and as an essential oil, for its supposed health benefits? It’s said to help memory, improve thyroid function, aid digestion, stimulate hair growth, lift mood, and ease anxiety.
The belief that rosemary boosts brain power dates back centuries. In ancient Greece, students are said to have worn garlands of rosemary to boost their memory, while Roman students rubbed the herb’s oil on their foreheads before exams. It even became a part of funeral ceremonies to help the living remember the dead. In Hamlet, Ophelia says, “There’s rosemary, that’s for remembrance.”
Rosemary has also been used in traditional Chinese medicine for headaches, indigestion, and insomnia. In colonial America, it was used for strokes, dizziness, and nervous conditions. As late as World War II, French nurses burned it as an antiseptic. And throughout the ages, it has served as a food preservative and fragrance.
Compounds in rosemary do have antioxidant and anti-inflammatory properties. In animal and test-tube studies, they have been shown to improve glucose and lipid metabolism, have stomach-protective properties, and reduce enzymes involved in the breakdown of acetylcholine (a neurotransmitter that plays a role in memory).
Though research in people is sparse, a recent small study in Therapeutic Advances in Psychopharmacology found that young adults who had the highest blood levels of a key rosemary compound following inhalation of the essential oil performed better and faster on some cognitive tasks. This suggests that volatile compounds in rosemary oil may be absorbed into the blood and perhaps even cross the blood-brain barrier. But the field of aromatherapy is hard to study, and these findings are preliminary. Interestingly, a study in the Journal of Medicinal Food found that low doses of rosemary (not much more than used in cooking) had positive effects on memory speed in older adults, while high doses worsened performance.
The Natural Standard, which reviews alternative and complementary medicine, says there is unclear, conflicting, or insufficient evidence for the use of rosemary for cognition, hair loss, anxiety/stress, constipation, arthritis, cardiovascular disease, diabetes, dyspepsia (indigestion), hyperthyroidism, and many other conditions for which it’s touted.
Bottom line: Given the lack of convincing evidence for health benefits, there’s no reason to take rosemary supplements. Plus, the same research that suggests benefits in animals also raises red flags about possible herb-drug interactions, contraindications, and side effects.
Especially avoid supplements if you are pregnant. There’s no harm in using the oil for its aroma. But never take it orally—even fairly low doses can be toxic, and large doses can be deadly. Allergic reactions to rosemary are also possible.