Rosemary has been used as medicine since the ancient Greeks. Its effects range from improving memory to growing hair.

However, in excess, rosemary may produce adverse effects. Read on to learn the benefits and limits of rosemary supplementation.

What Is Rosemary?

Rosemary (R. officinalis) is a widely used herb that originates from the Mediterranean region. It dates back to the ancient Greeks who hailed the plant for assisting memory and stimulating the brain [1].

The plant contains an essential oil that is needed for survival and known to boost memory [1].

Rosemary is known to have one of the highest antioxidant properties of spices and can combat fungus, bacteria, and cancer [2].

The antioxidant properties of rosemary extracts differ due to [2]:

  • Genetic and growth conditions
  • Geographical origin
  • Climatic conditions
  • Extraction process
  • Quality of original plant
  • Harvesting date
  • Storage and processing

Rosemary can be taken in a wide range of forms including [1, 3, 4, 5, 6]:

  • Powder
  • Tea
  • Extracts
  • Oil

The different forms of rosemary can produce different effects. The extracts especially differ depending on how the rosemary is extracted and what compounds are extracted.

What It’s Made of

Rosemary is made up of a wide variety of oils, phenolic acid derivatives, and phenolic diterpenes including [7]:

  • Oils like 1,8-cineole, α-pinene, camphene, α-terpineol, borneol with antioxidant, antimicrobial, and anticancer effects [R, R].
  • Phenolic acid derivatives:
    • Rosmarinic acid, found heavily in the leaves, protects the lungs and fights Alzheimer’s [8, 9].
    • Carnosic acid, which protects the brain and has strong antioxidant properties [10, 11, 11].
  • Phenolic diterpenes like carnosol, which has antioxidant effects, protects the liver and improves cognition in Alzheimer’s patients [12, 13, 7].

Rosemary Health Benefits

1) Rosemary Improves Brain Function

In a study (B-RCT) of 144 volunteers, aromatherapy with rosemary improved working memory performance, memory quality, and increased alertness. However, memory speed declined compared to controls [14].

In a trial (DB-RCT) of 28 elderly subjects, low doses (750 mg) of rosemary powder improved memory speed. However, at larger doses (>1500 mg) memory speed, attention, and quality of memory declined [1].

Volunteers (20) scored better and more accurately in simple subtraction tests, even with decreased reaction times [15].

Finally, rosemary tea reduced depression in mice [3].

2) Rosemary Protects the Brain

Carnosic acid protects neurons from oxidative stress and overstimulation [11].

Carnosic acid builds up in nerve cells and other protective cells in the brain [11].

A rosemary extract also enhanced the production of NGF [4].

Carnosic acid protects part of the brain (middle cerebral artery) from tissue damage (ischemia/reperfusion injury). It reduced blood clots and brain swelling in rats [11, 16].

Carnosic acid protects against oxidative stress, which can cause Alzheimer’s and reduced cell death in rat brains (hippocampus) [17].

Rosemary also prevents beta-amyloid plaques, one of the leading causes of Alzheimer’s [18].

Other cognitive disorders, such as dementia and ataxia, are treated by suppressing acetylcholinesterase (AChE). Rosmarinic acid suppressed AchE by 85.8%, even at low doses [9].

3) Rosemary Can Fight Cancer

In human ovarian cancer cells, some active rosemary constituents stopped cancer cell growth and killed existing cancer cells [19].

There is a vast array of data supporting rosemary’s effectiveness against varieties of cancers including [20, 21]:

  • Leukemia
  • Colon
  • Pancreas
  • Breast
  • Prostate
  • Ovaries
  • Cervix
  • Bladder
  • Liver
  • Lung

Both rosmarinic acid and rosemary extracts decreased heterocyclic amines (HCAs), which are cancer-causing molecules found in meats such as beef, chicken, pork, and fish [22].

Rosemary extracts with the highest carnosic acid concentration were the most effective. In liver cancer cells, carnosic acid decreased cell viability from 83.05 to 2.5% [23, 12, 24].

4) Rosemary Protects the Skin

In a study of 10 healthy subjects, rosemary extracts protected the skin from UV damage, increasing its effectiveness with time [5].

More skin cells survived in the volunteers who received rosemary extracts. This protection helps reduce aging, cancer, or UV light damage [5, 6].

Rosemary oil is also effective against bacteria (P. acnes) that cause acne [6].

5) Rosemary Improves Asthma

In a study of 40 asthma patients (DB-RT), rosemary extracts decreased asthma symptoms such as [25]:

  • Wheezing
  • Chest pain
  • Coughing
  • Production of sputum (a mixture of saliva and mucus)

Additionally, rosmarinic acid and rosemary extracts decreased the production of asthma-induced inflammatory cells (eosinophils, neutrophils, and mononuclear cells) in rats [26].

6) Rosemary Limits Weight Gain

In rats fed high-fat diets, rosemary extracts decreased weight gain by 64% and fat gain by 57% compared to controls [27].

Another study found similar results (69% improvements compared to the controls). While the extract did not decrease food intake, it increased fat loss [28].

7) Rosemary Has Antioxidant Properties

In one study, rosemary extracts contained antioxidant properties. The strength of the antioxidant effects increased with extraction time [2].

Rosemary extracts were better at stopping oxidative damage than commonplace antioxidants such as butylated hydroxytoluene (BHT), Trolox, and ascorbic acid [29, 24].

8) Rosemary Is Antimicrobial

Rosemary extracts completely stopped bacterial growth in multiple strains of bacteria (Gram-positive and Gram-negative). The effects were more pronounced for the Gram-positive bacteria [2].

In one study, extracts were able to inhibit 28 of 29 bacterial strains studied [30, 31, 32].

Rosemary also has antifungal properties [2, 32, 33].

Rosemary extracts showed antiviral properties against HIV, but at harmful concentrations [34].

Carnosol is a non-toxic compound of rosemary that also has antiviral properties. However, it was not as effective as the rosemary extract [34].

9) Rosemary Has Anti-Inflammatory Properties

At higher doses, rosemary extracts decreased the production of inflammatory molecules (such as IL-1β, COX-1, TNFα, and iNOS) in human cells [35].

It decreases the production of nitric oxide, a product of inflammation [24].

Rosemary essential oil significantly reduced white blood cell (leukocyte) rolling, another process of the inflammatory response [36].

10) Rosemary Prevents Blood Clots

Cell and mice studies found that rosemary possessed antithrombotic effects, meaning it stopped blood from clotting and restricting blood flow [37].

This effect was most likely because rosemary stops platelet activity, which are the molecules responsible for the clotting of blood [37].

11) Rosemary May Have Antiulcer Properties

Rat studies proved that rosemary has antiulcer properties. A rosemary extract decreased ulcers from 44-51.8% in rats depending on the type of extract. The antioxidant compounds in rosemary help bring about this effect [38].

12) Rosemary Helps the Gut

Rosemary extract:

  • Relieves gas [39].
  • Decreased infections (in rats with colitis/infection of the colon) [40].
  • Discharges bile [39].
    • This decreases the chances of infection, and bile buildup can reduce your gut’s defense mechanisms [41].
  • Increased bile flow (in rats) [42].
    • This helps discharge bile.
  • Discharged urine (in rats) [43]
    • Urine buildup can cause uremia, which is an overflow of waste products in the blood. Urine retention is also common in people with thyroid problems [44].

It can also potentially help fight gut diseases like IBS [40].

13) Rosemary Protects the Liver

Carnosol (found in rosemary) prevented liver damage in rats [13].

Carnosol consumption decreased malondialdehyde, a marker of oxidative stress in the liver, by 69%. It also protected the liver tissue from distorting and prevented liver glycogen (energy storage molecules) from depleting [13].

Rosemary extracts decreased plasma glutamic-pyruvic transaminase, a marker of liver injury, by 72% in rats [42].

14) Rosemary Protects the Lungs

Giving rabbits rosmarinic acid (found in rosemary) supplements prevented fluid accumulation in the lungs [8].

15) Rosemary Reduces Pain

In traditional medicine, rosemary has been used to fight painful menstruation (dysmenorrhea), especially stomach cramps and kidney colic pain, which is pain caused by blockage of urine from the kidney to the bladder [45].

Rosemary oil also increased the time it took for rats to respond to heat-induced pain [45].

16) Rosemary May Reduce Spasms

Rosemary leaves have antiepileptic properties [39, 46].

It reduces involuntary muscle spasms. Studies of guinea pigs found that rosemary oil reduced spasms in the heart (ileum and atria) [47].

17) Rosemary Improves Mood

In a study of 144 volunteers, the smell of rosemary brought about feelings of content, much more so than those smelling lavender or no smell at all [14].

Mice supplemented with rosemary leaf infusions showed less anxiety [3].

18) Rosemary Helps Reduce Cough

Rosemary leaves help release mucus and saliva (sputum) to heal coughs [39, 46].

19) Rosemary Helps Grow Hair

In a study (DB-RCT) of 50 patients with androgenetic alopecia (permanent balding), rosemary oil increased hair counts significantly after six months [48].

20) Rosemary May Increase Movement

Rosemary oil consumption increased movement/activity in rats. The greater activity is due to increases in 1,8-cineole [49].

21) Rosemary Combats Arthritis

Rosemary combats the progression of rheumatoid arthritis by reducing oxidative damage to the joints and surrounding tissues [39].

Side Effects of Rosemary Consumption

1) Rosemary Supplementation May Reduce Fertility

Rat’s reproductive organs became smaller after long-term rosemary leaf extract consumption. It also decreased sperm count, mobility, and density. All of these factors negatively affect fertility. Also, pregnant female rats had more fetal loss [50].

2) Rosemary Increases Scalp Itching

In a study (DB-RCT) of 50 permanent balding patients, using rosemary oil to help grow hair increased scalp itching [48].

3) Rosemary May Increase Blood Glucose Levels

Rosemary can raise blood glucose levels. Rabbits with induced diabetes increased glucose levels by 55% in two hours [51].

4) Rosemary Oils May Irritate the Skin

In individuals with highly sensitive skin, bath preparations with rosemary oils may cause dermatitis or reddening of the skin (erythema) [52].

5) Rosemary May Induce Convulsions

Although rosemary can reduce convulsions, at high doses of camphor, a compound in rosemary may actually cause epilepsy-like convulsions [53].


Many of the mentioned studies use high concentrations of rosemary extract to see the intended effects. Therefore, experiencing many of the effects, such as anticancer, might be unlikely with everyday rosemary consumption [54].


Pregnant women are advised not to consume rosemary in excess because it may induce abortion. Breastfeeding women are also advised to use rosemary in moderation [55, 56].

Diabetics and people with high blood sugar are also advised to consume rosemary in moderation as it can raise blood glucose levels [51].


A meta-analysis found doses of rosemary extract at 0.1-100 μg/mL to be most effective in fighting cancer. However, an effective dose for human use has not been established due to the wide range of concentrations used in different studies [54].

Overall, the rosemary plant is classified as safe by the FDA and found to have very low toxicity in rats even at high concentrations and extended periods of time [54, 57].

It is recommended to take 4-6 g of rosemary dry leaf/twig supplements daily and 2-4 mL of liquid extracts three times daily [52].

Drug Interactions

1) Rosemary with Cancer Drugs

Rosemary extract in conjunction with cisplatin, an anticancer drug, increased the effectiveness of the drug against human ovarian cancer cells by 50% to 85% [19].

Using rosemary extract with 5-fluorouracil, the most common drug against colorectal cancer improved outcomes by suppressing genes that contribute to drug resistance [58].

Rosmarinic acid with certain Vitamin D derivatives increased the drug’s effectiveness in multiple leukemia studies [59, 10].

2) Rosemary with Pain Relievers

Rosemary oil with common pain relievers like codeine and Tylenol increased pain tolerance in rats [45].

Synergies with Other Supplements

In a study of 12 volunteers, rosemary extracts with citrus supplements protected the skin against UV damage better than each supplement alone [5].

User Reviews

One user noted that rosemary helped her with her very oily skin. Another user saw good improvements in memory and improving brain fog.

Other people use the product to improve hair loss and intestinal problems [60].


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