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 .
The plant contains an essential oil that is needed for survival and known to boost memory .
Rosemary is known to have one of the highest antioxidant properties of spices and can combat fungus, bacteria, and cancer .
The antioxidant properties of rosemary extracts differ due to :
- Genetic and growth conditions
- Geographical origin
- Climatic conditions
- Extraction process
- Quality of original plant
- Harvesting date
- Storage and processing
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 :
- Oils like 1,8-cineole, α-pinene, camphene, α-terpineol, borneol with antioxidant, antimicrobial, and anticancer effects [R, R].
- Phenolic acid derivatives:
- 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 .
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 .
Volunteers (20) scored better and more accurately in simple subtraction tests, even with decreased reaction times .
2) Rosemary Protects the Brain
Carnosic acid builds up in nerve cells and other protective cells in the brain .
Carnosic acid protects against oxidative stress, which can cause Alzheimer’s and reduced cell death in rat brains (hippocampus) .
Rosemary also prevents beta-amyloid plaques, one of the leading causes of Alzheimer’s .
3) Rosemary Can Fight Cancer
In human ovarian cancer cells, some active rosemary constituents stopped cancer cell growth and killed existing cancer cells .
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 .
4) Rosemary Protects the Skin
Rosemary oil is also effective against bacteria (P. acnes) that cause acne .
5) Rosemary Improves Asthma
In a study of 40 asthma patients (DB-RT), rosemary extracts decreased asthma symptoms such as :
- Chest pain
- Production of sputum (a mixture of saliva and mucus)
6) Rosemary Limits Weight Gain
Another study found similar results (69% improvements compared to the controls). While the extract did not decrease food intake, it increased fat loss .
7) Rosemary Has Antioxidant Properties
In one study, rosemary extracts contained antioxidant properties. The strength of the antioxidant effects increased with extraction time .
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 .
Rosemary extracts showed antiviral properties against HIV, but at harmful concentrations .
Carnosol is a non-toxic compound of rosemary that also has antiviral properties. However, it was not as effective as the rosemary extract .
9) Rosemary Has Anti-Inflammatory Properties
It decreases the production of nitric oxide, a product of inflammation .
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 .
This effect was most likely because rosemary stops platelet activity, which are the molecules responsible for the clotting of blood .
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 .
12) Rosemary Helps the Gut
- Relieves gas .
- Decreased infections (in rats with colitis/infection of the colon) .
- Discharges bile .
- This decreases the chances of infection, and bile buildup can reduce your gut’s defense mechanisms .
- Increased bile flow (in rats) .
- This helps discharge bile.
- Discharged urine (in rats) 
- 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 .
It can also potentially help fight gut diseases like IBS .
13) Rosemary Protects the Liver
Carnosol (found in rosemary) prevented liver damage in rats .
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 .
Rosemary extracts decreased plasma glutamic-pyruvic transaminase, a marker of liver injury, by 72% in rats .
14) Rosemary Protects the Lungs
Giving rabbits rosmarinic acid (found in rosemary) supplements prevented fluid accumulation in the lungs .
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 .
Rosemary oil also increased the time it took for rats to respond to heat-induced pain .
16) Rosemary May Reduce Spasms
It reduces involuntary muscle spasms. Studies of guinea pigs found that rosemary oil reduced spasms in the heart (ileum and atria) .
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 .
18) Rosemary Helps Reduce Cough
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 .
20) Rosemary May Increase Movement
Rosemary oil consumption increased movement/activity in rats. The greater activity is due to increases in 1,8-cineole .
21) Rosemary Combats Arthritis
Rosemary combats the progression of rheumatoid arthritis by reducing oxidative damage to the joints and surrounding tissues .
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 .
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 .
3) Rosemary May Increase Blood Glucose Levels
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) .
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 .
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 .
Diabetics and people with high blood sugar are also advised to consume rosemary in moderation as it can raise blood glucose levels .
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 .
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 .
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% .
Using rosemary extract with 5-fluorouracil, the most common drug against colorectal cancer improved outcomes by suppressing genes that contribute to drug resistance .
2) Rosemary with Pain Relievers
Rosemary oil with common pain relievers like codeine and Tylenol increased pain tolerance in rats .
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 .
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 .
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