Traditional practitioners call tulsi (or holy basil) the “Queen of Herbs” and believe it can help the body deal with stress. What does the science say about its many purported benefits? Read on to find out.
What is Tulsi or Holy Basil?
Tulsi or holy basil [Ocimum sanctum or Ocimum sanctum Linn) is an important herb in Ayurvedic medicine (the traditional medicine of India). It is especially known as an adaptogen, an herb that supports the body’s stress response (whether physical, chemical, metabolic, or psychological) .
It is known as the “Queen of Herbs” and in Sanskrit means ‘the incomparable one.’ In fact, Hinduism links the tulsi plant to the figure of a goddess .
Tulsi is believed to promote long life and is taken as an elixir to promote balance and resilience to all of life’s challenges .
Traditional indications for this herb include common colds, bronchitis, diarrhea, stomach disorders, headaches, inflammation, arthritis, heart disease, skin diseases, eye diseases, various forms of poisoning, insect bites, and malaria .
Tulsi is from the Lamiaceae (mint) family of herbs and alternatively may be called Ocimum tenuiflorum Linn, Tulasi, or Holy Basil (a direct translation from the Latin, Ocimum sanctum) .
Different parts of the herb have been used medicinally, including the leaves, stem, flower, root, seeds, and even the whole plant .
It may be taken as an herbal tea, dried powder, or fresh leaf used in cooking traditional dishes .
Constituents of Tulsi (Holy Basil)
Active compounds in whole tulsi leaves include [R, 2):
- Eugenol (1-hydroxy-2-methoxy-4-allylbenzene) is largely responsible for the therapeutic effects of the herb
- Oleanolic acid
- Ursolic acid
- Rosmarinic acid
- β-caryophyllene [R, 2):
- Eugenol (67.4% – 72.8%)
- β-elemene (11.0% – 10.9%)
- β-caryophyllene (7.3% – 8.4%)
- Germacrene D (2.4% – 2.2%)
- Linalool (54.95%)
- Methyl chavicol (methyl carvicol – also called Estragol) (11.98%)
- Methyl cinnamate (7.24%)
- Linolen (0.14%) [R].
- Protein: 30 Kcal, 4.2 g
- Fat: 0.5 g
- Carbohydrate: 2.3 g
- Vitamins: vitamin C (25 mg vitamin C per 100 g) and vitamin A
- Minerals: Calcium: 25 mg; Phosphorus 287 mg; Iron: 15.1 mg
- Phytonutrients: Chlorophyll and many other phytonutrients 
Holy Basil Benefits
Due to insufficient clinical studies, tulsi supplements have not been approved by the FDA for medical use. Further research will be required to determine whether tulsi is effective or safe for long-term use. Talk to your doctor before using tulsi supplements to avoid unexpected interactions.
1) Stress and Anxiety
Tulsi is a calming herb that produces relaxation effects. However, on its own tulsi does not induce drowsiness or sleep.
Tulsi prevented stress-induced changes in blood levels of corticosterone (in rats; comparable to cortisol levels in humans) .
Tulsi constituents ocimarin and the ocimumosides A and B show antistress activity including normalizing blood sugar levels and cortisol levels at a dosage 40 mg/kg (in rats) .
In a randomized, double-blind, placebo-controlled study of 158 patients ages 18 – 65, OciBest, the whole plant extract of Tulsi, was found to be 1.6 times or 39 percent more effective in the management of stress symptoms than the placebo over a six-week time period .
In a study of 35 subjects with Generalized Anxiety Disorder, taking tulsi (500 mg) with two meals daily reduced anxiety and feelings of depression over a two-month period .
An alcohol extract of Tulsi root (400 mg/kg) is a CNS stimulant or an anti-stress agent in mice. It was as effective as the antidepressant desipramine, commonly sold as Norpramin .
Tulsi essential oil had strong anti-inflammatory effects in an animal model of granulomatous disease .
A study on tulsi extract showed significant anti-inflammatory activity in human cells, validating its traditional use in treating cardiovascular disease .
A purified extract of the fresh leaves and stems of tulsi yielded appreciable amounts of eugenol, as well as the following compounds: cirsilineol, cirsimaritin, isothymusin, isothymonin, apigenin, and rosmarinic acid .
The anti-inflammatory activity of these compounds was comparable to ibuprofen, naproxen, and aspirin at 10-, 10-, and 1000-microM concentrations, respectively .
3) Cognitive Function
In rats, tulsi promotes memory and attention by inhibiting acetylcholinesterase, thus increasing acetylcholine levels .
A water extract of dried tulsi protected against drug- and aging-induced memory problems in mice, indicating that tulsi may be beneficial in the treatment of cognitive disorders such as Alzheimer’s disease and dementia .
While promising, all of these studies were conducted in animals. Future research will determine whether tulsi is at all effective in humans.
4) Heart Health
An alcohol extract of tulsi leaves reduced heart tissue inflammation in a mouse model of a heart attack (myocardial infarction), possibly due to its high phenol content .
Tulsi extract may prevent cardiovascular disease by inhibiting myeloperoxidase (MPO), an oxidative enzyme that may cause plaque accumulation in the arteries (known as atherosclerosis) .
A study on tulsi extract showed significant anti-inflammatory activity in human cells, validating its traditional use in treating cardiovascular disease .
Tulsi leaf essential oil was shown to lower cholesterol and protect the heart via its antioxidant effects (in rat studies) .
In a study of rabbits, tulsi leaf significantly decreased blood levels of cholesterol, triacylglycerol (formerly called triglycerides), and LDL cholesterol with a significant increase in HDL cholesterol .
Again, however, all of these studies were conducted in animals or cells. Future human trials will provide better-quality data.
5) High Blood Pressure
Because tulsi is rich in potassium (18,991 µg/g), according to a trace element study, some researchers are studying whether it can reduce blood pressure .
In a cell study, the tulsi extract/fractions eugenol and tulsi oil inhibit ACE (an enzyme that increases blood pressure) in a concentration-dependent manner and therefore may help reduce blood pressure .
Note that these are extremely early results that have not yet been studied in humans, or even in animals. Clinical studies will be required to determine whether tulsi is effective for this purpose.
6) Diabetes and Blood Sugar Imbalance
In a small study of type 2 diabetes patients, tulsi lowered fasting blood sugar levels by 17.6% and post-meal blood sugar levels by 7.3%. While promising, these results will need to be repeated in larger, higher-quality studies to determine whether tulsi is really effective for this purpose .
A water-based extract of tulsi decreased blood sugar levels in a study of diabetic rats .
7) Liver Health
An alcohol extract of tulsi leaf at 200 mg/kg body weight per day was shown to protect the liver from toxin-induced damage (in rats) .
No human studies have been conducted to investigate tulsi’s effect on liver health.
8) Stomach Ulcers
An alcohol extract of tulsi leaves (eugenol content 5%) at a dose of 50 – 200 mg/kg, twice daily for five days orally, was dose-dependently protective against some types of stomach ulcers (alcohol-induced, but not aspirin-induced) .
In a study of rats and guinea pigs, tulsi protected against a variety of ulcer-inducers, including aspirin, alcohol, and histamine .
Once again, this potential benefit has only been studied in animals. Human studies will be required.
Strong antioxidant capacity was measured from Tulsi essential oil and was particularly correlated with its eugenol content .
Tulsi leaf powder was shown to combat cadmium-produced free radicals and restored liver and kidney functions in a study of broiler chickens .
Human studies have not yet been conducted. Future research will determine the extent of tulsi’s antioxidant capacity in humans.
Animal studies (mice) showed an alcoholic leaf extract of tulsi reduced signs of pain, indicating potential as an analgesic .
Another rat study showed that for both an alcohol extract of tulsi and an aqueous suspension of tulsi (500 mg/kg) were as effective as 300 mg of the NSAID, sodium salicylate .
Once again, this effect has only been studied in animals. Future research will determine whether tulsi is or contains an effective painkiller for humans.
11) Immune Function (Th1 and Th2)
Daily ingestion of 300 mg capsules of tulsi leaf extract significantly increased IFN-y, IL-4, and T-helper cells, and natural killer cell activity – all important components of the immune system – after four weeks of intervention in 24 healthy volunteers .
Tulsi appears to increase both the Th1 and Th2 immune responses .
Larger studies will determine the extent of tulsi’s effect on the immune system and whether it could be useful in any clinical situations.
Tulsi is currently being studied for its potential usefulness against skin cancer, lung cancer, and breast cancer and potential preventative effects against liver cancer, stomach cancer, and oral cancer .
The research we discuss below is still in the animal and cell stages. Future studies will determine whether any of tulsi’s active compounds are useful in cancer therapies. Do not under any circumstances attempt to replace conventional cancer therapy with supplements like tulsi. If you want to use tulsi as a supportive measure, talk to your doctor to avoid any unexpected interactions.
In mice, an alcoholic extract of tulsi leaves applied topically was protective against chemically-induced skin cancer .
Pre-treatment with an alcoholic extract of tulsi leaves decreased the number of tumors induced by a range of skin carcinogens in a mouse model of skin cancer .
In another study, a water-alcohol extract of tulsi reduced tumor size and increased survival rates of mice with melanoma .
Tulsi seed oil was also protective against the development of skin cancer and improved survival rates of mice with tumors .
In a review study, a tulsi alcohol extract induced cell death in human lung cancer cells and suppressed the growth of lung cancer cells in mice .
In mice, tulsi extracts reduced MMP9 activity, thus reducing the formation of tumors when tumor cells were injected into the animals .
Tulsi extract reduced the formation of tumors in mice injected with lung cancer cells .
Phytochemicals contained in tulsi, including carnosic acid, rosmarinic acid, and luteolin are able to inhibit the growth of lung cancer .
Cell studies have shown that tulsi leaf extract prevented the spread of breast cancer and prevented an increase in the levels of COX–2/inflammation .
In cell-based studies, Eugenol (a primary constituent of Tulsi), luteolin, and apigenin killed human breast cancer cells [R, 36].
Carnosic acid and rosmarinic acid were shown to inhibit the growth of human breast cancer cells .
Tulsi (leaf alcohol extract) protected liver cells from DNA damage and increased antioxidant levels in response to cancer-causing chemicals and drug exposures .
In rats, tulsi significantly prevented chemical-induced liver cancer .
Additional anti-cancer effects were also observed in liver cells from the tulsi phytochemicals apigenin, luteolin, carnosic acid, and rosmarinic acid .
Studies have shown that including tulsi leaves in the diet prevented chemically–induced stomach cancer in mice .
An alcohol-based 70% tulsi leaf extract reduced chemical–induced stomach cancer in rats .
In an animal study (rats), tulsi selectively induced cell death in chemical-induced stomach cancer, but not in the normal stomach tissue .
Cell culture studies have shown that phytochemicals in tulsi, luteolin, β-sitosterol, ursolic acid, and apigenin also inhibit growth and kill stomach cancers .
In a study of 41 patients in India (aged 17 – 56 years), tulsi combined with turmeric was shown to be highly potent against Oral Submucous Fibrosis (OSMF), which if not treated, can progress to oral cancer .
In hamsters, water extract of tulsi taken by mouth had the greatest anticancer activity against papillomas and squamous cell carcinomas .
In a cell study, tulsi water extract was shown to be highly effective against oral cancer cells .
Two flavonoids in tulsi, orientin (a derivative of luteolin) and vicenin (an apigenin), have been shown to protect human blood cells from radiation-induced DNA damage .
19) Bone Healing
A tulsi extract significantly reduced the healing time after a jaw fracture in 29 patients. Tulsi may increase calcium uptake, bone calcification, or enzymes involved in bone remodeling, such as alkaline phosphatase .
Tulsi essential oil showed strong antibacterial activity against antibiotic-resistant Staphylococcus, Enterococcus, and Pseudomonas bacteria species .
A fatty oil of tulsi also showed strong antibacterial activity against Staphylococcus aureus, Bacillus pumilus, and Pseudomonas aeruginosa, and had the greatest effectiveness against S. aureus .
A water extract of tulsi (60 mg/kg) was more effective than an alcohol-based extract against Klebsiella, E. coli, Proteus, S. aureus and Candida albicans. However, the alcohol-based extract showed better inhibition of Vibrio cholerae (the bacteria that causes cholera) .
In a cow model of mastitis, tulsi extract injected into the breast tissue lowered the total bacterial count and enhanced the immune system .
These results have, thus far, been limited to cell studies. Future research will determine whether any of tulsi’s active compounds will work as an effective antibiotic.
Apigenin, a compound derived from Tulsi, has shown effectiveness against H1N1 and Swine Flu [R].
An alcohol- or solvent-based extract of tulsi inhibited genital herpes (Herpes Simplex Virus type 2) in a cell-based study .
An aqueous extract of tulsi leaves prevented the cell damage and the growth of New Castle Disease (NCD) virus in chickens .
22) Candida Overgrowth
This may in part be due to its constituent, eugenol, which on its own has been found to inhibit candida .
Rosmarinic acid, another compound found in tulsi, also disrupts biofilms, but only in higher concentrations (in mouse intestinal cells) .
As is the case with its antibacterial potential, tulsi’s effect on biofilms has not yet been studied in humans.
In a rabbit study, treatment with 2 g/day of fresh tulsi leaves significantly increased testosterone levels over a 30 day period. It is unclear what kind of effect tulsi could have on human testosterone levels, as this has not yet been studied .
25) Histamine Intolerance
In rats, 5 and 10 mg/kg of tulsi extract reduced the incidence of cataracts by 20% and 60% respectively, in part by raising levels of antioxidant enzymes .
Tulsi was shown to possess significant anticataract activity in rat lenses, which may be due to its inhibition of aldose reductase – an enzyme that caused cataracts in diabetes .
This potential benefit has not yet been studied in humans.
27) Graying Hair
Tulsi increases catalase, the enzyme that breaks down hydrogen peroxide, and therefore may keep hair from graying. This is a purely speculative potential benefit, however, and it required further study [75, 76].
Tulsi Side Effects & Precautions
Studies using rats have not shown any toxicity at the highest dose (1000 mg/kg/day of alcohol/aqueous extract over 28 days) .
Another study using a standardized extract of Ocimum sanctum (OciBest™) showed no destructive effect on genes .
The safety of taking tulsi during pregnancy and breastfeeding has not yet been studied, and so taking tulsi during those times is best avoided until more is known .
Tulsi may not be good for those with thyroid disease. An animal study found that tulsi at the dose of 0.5 g/kg bodyweight for 15 days significantly decreased serum T4 concentration; however, no marked changes were observed in serum T3 level, T3/T4 ratio and in the concentration of serum cholesterol .
Taking Tulsi with Valium may increase its effects on the immune system. Co-administration of diazepam (1 mg/kg, sc), a benzodiazepine, with Tulsi seed oil (1 ml/kg, IP) enhanced the effect of the tulsi on the immune system (in rats) .
Flumazenil (5 mg/kg), an antidote to benzodiazepines (central benzodiazepine receptor antagonist), inhibited the immune system enhancement of tulsi seed oil (in rats) .
Genes that have a direct role in the buildup of plaque in the arteries (atherosclerosis) include LDRL, LxRalpha, PPARs, and CD-36, because these genes control fatty acid metabolism, the production of substances that are toxic to cells, and the activities of cells in the walls of the arteries .
Polyphenols in tulsi were found to have the inherent ability to inhibit the cellular production (transcription) from these genes .
The authors of the study concluded, “on the basis of these results, we propose for the first time that HPLC purified polyphenolic fraction IV of tulsi may have a profound antiatherogenic effect” .
Holy basil is available as a supplement or as a fresh herb for cooking or steeping into tea. Look for recipes incorporating holy basil on Thai cooking sites.
People typically take 500 mg of tulsi leaf extract twice daily for neurological and adaptogenic effects. However, without clinical studies for the express purpose of finding a safe and effective dose, there is no medically appropriate dose. Talk to your doctor about supplementing with tulsi to avoid any unexpected interactions.