Rosemary (Rosmarinus officinalis) is widely used as a spice when cooking, especially in Mediterranean dishes. It is also used for fragrance in soaps and cosmetics. Traditionally, rosemary has been used medicinally to:
- Improve memory
- Relieve muscle pain and spasm
- Stimulate hair growth
- Support the circulatory and nervous systems
It is also believed to increase menstrual flow, act as an abortifacient (causing miscarriage), increase urine flow, and treat indigestion. Almost none of these uses have been studied scientifically in humans. However, one study in humans found that long-term daily intake of rosemary prevents thrombosis.
In the lab, rosemary has been shown to have antioxidant properties. Antioxidants can neutralize harmful particles in the body known as free radicals, which damage cell membranes, tamper with DNA, and even cause cell death. Also in the lab, rosemary oil appears to have antimicrobial properties (killing some bacteria and fungi in test tubes). It isn't known whether rosemary would have the same effect in humans.
Rosemary leaf is used in Europe for indigestion (dyspepsia) and is approved by the German Commission E, which examines the safety and efficacy of herbs.
Muscle and joint pain
Applied topically (to the skin), rosemary oil is sometimes used to treat muscle pain and arthritis and improve circulation. It is approved by the German Commission E for these purposes. However, there is no scientific evidence that it works.
Historically, rosemary has been used to stimulate hair growth. In one study of 84 people with alopecia areata (a disease in which hair falls out, generally in patches), those who massaged their scalps with rosemary and other essential oils (including lavender, thyme, and cedarwood) every day for 7 months experienced significant hair regrowth compared to those who massaged their scalps without the essential oils. But the study was not well designed, and it is impossible to say whether rosemary caused the hair growth.
Neutralize food-borne pathogens
Several studies show that rosemary inhibits food-borne pathogens like Listeria monocytogenes, B. cereus, and S. aureus.
Improve memory or concentration
Rosemary is often used in aromatherapy to increase concentration and memory, and to relieve stress. One study suggests that rosemary, combined with other pleasant-smelling oils, may lower cortisol levels and help reduce anxiety. Another study found that the use of lavender and rosemary essential oil sachets reduced test taking stress in graduate nursing students.
Several studies suggest that rosemary extract may inhibit tumor growth by preventing cancerous cells from replicating. One study found that rosemary, on its own and in combination with curcumin, helped prevent breast cancer. A second study found similar effects of rosemary on colon cancer cells.
The use of herbs is a time-honored approach to strengthening the body and treating disease. However, herbs can trigger side effects and interact with other herbs, supplements, or medications. For these reasons, you should take herbs with care, under the supervision of a health care provider.
Rosemary is generally considered safe when taken in recommended doses. However, there have been occasional reports of allergic reactions. Because of their volatile oil content, large quantities of rosemary leaves can cause serious side effects, including vomiting, spasms, coma and, in some cases, pulmonary edema (fluid in the lungs).
Because higher doses of rosemary may cause miscarriage, pregnant and nursing women should not take rosemary as a supplement. But it is safe to eat as a spice in food.
People with high blood pressure, ulcers, Crohn's disease, or ulcerative colitis should not take rosemary.
Rosemary oil can be toxic if ingested and should never be taken orally.
Antiplatelet and anticoagulant drugs (blood thinners)
Rosemary may affect the blood's ability to clot. It could interfere with any blood-thinning drugs you are taking, including:
- Warfarin (Coumadin)
- Clopidogrel (Plavix)
Rosemary may interfere with the action of ACE inhibitors taken for high blood pressure, including:
- Captopril (Capoten)
- Elaropril (Vasotec)
- Lisinopril (Zestril)
- Fosinopril (Monopril)
Diuretics (water pills)
Rosemary can act as a diuretic, raising your risk of dehydration. It can increase the effects of diuretic drugs, including:
- Furosemide (Lasix)
Because of its diuretic effects, rosemary might cause the body to lose too much water, and the amount of lithium in the body can build up to toxic levels.
Rosemary may alter blood sugar levels and could interfere with drugs taken to control diabetes.
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