Rosemary: what the evidence says about memory, hair and the kitchen

Rosemary is a woody Mediterranean herb, also listed by botanists as Salvia rosmarinus Moss 2018, used fresh or dried with roasts, potatoes, beans and breads. FDA lists rosemary among the spices and natural seasonings generally recognized as safe for their intended use in food FDA. At normal cooking amounts it is a flavoring, and the trial doses below are higher or in different forms.

"There's rosemary, that's for remembrance" is Shakespeare, not science, but researchers have tested it. In a 2003 trial, 144 adults did a computerized test battery in a cubicle scented with rosemary oil, lavender oil or nothing. They were told the study was about something else, to limit expectation effects. Rosemary improved overall quality of memory and secondary memory but slowed speed of memory, and the rosemary group felt more alert afterward than the other two groups Moss 2003.

Eaten rosemary has been tested too. In 28 older adults (mean age 75), a single 750 mg dose of dried rosemary leaf powder, close to culinary amounts, improved speed of memory compared with placebo, while the highest dose, 6,000 mg, impaired it, and other measures showed some harmful effects Pengelly 2012. More is not better here. In 68 university students, 500 mg capsules twice a day for a month improved self-reported memory, anxiety, depression and sleep scores Nematolahi 2018, and in 80 healthy adults a 250 mL bottle of commercial rosemary water produced small improvements on some cognitive tasks Moss 2018.

These trials are small, short and mostly from a few research groups, so they are a reason for curiosity rather than a memory plan. A sprig on the windowsill or rosemary in your cooking costs little either way.

The hair claim comes from one trial. Researchers in Iran randomly assigned 100 people with androgenetic alopecia (pattern hair loss) to rosemary oil or 2% minoxidil for six months. Neither group gained hair at three months; both had significantly higher hair counts at six months, with no difference between groups, and scalp itching was more common with minoxidil Panahi 2015. With no placebo group and a single trial, it cannot show how much of the gain came from the oil itself, and 2% is a lower strength of minoxidil than many people use.

Essential oil is concentrated: the EU monograph on rosemary oil for skin use says not to apply it to broken or irritated skin, to keep it away from eyes and mucous membranes, and that use under 18 has not been establishedEMA. Dilute it in a carrier oil and patch-test first. For culinary rosemary, dried herb or tea, iHerb lists dried rosemary and rosemary products.