Tulsi (also known as Ocimum sanctum or holy basil) is an aromatic plant in the mint family (Lamiaceae) native to India and Southeast Asia.^[5] It is rich in various bioactive phytochemicals, including rosmarinic acid, apigenin, ursolic acid, caffeic acid, ferulic acid, and eugenol.^[1][5] Tulsi is used primarily as a medicinal herb, and it is distinct from sweet basil (Ocimum basilicum), which is more often used as a culinary herb.^[5] Despite a long history of use as a traditional medicine, very little clinical research exists.

Tulsi is proposed to have antimicrobial, immune-modulating, anti-cancer, anti-inflammatory, antioxidant, adaptogenic (increasing the body’s resilience to stress), and antidiabetic properties. While these effects have been demonstrated in animal models, very little research has been done in humans. Most clinical trials have lacked a placebo control, among other methodological limitations, and many outcomes have not been replicated.

Tulsi seems to have antimicrobial and anti-inflammatory properties that may be beneficial for periodontal disease.^[6][7] Preliminary research has found reductions in the symptoms and severity of gingivitis and periodontitis with the local use of tulsi as a gel, toothpaste, or mouth rinse. Some studies reported reductions in plaque and improved gum health (less inflammation and bleeding and better gum attachment).^{[3][4][8][9][10]}

Tulsi may also have beneficial effects on metabolic health, but research is mixed. Improvements in lipid profiles and glycemic control have been reported, including reduced blood glucose, hemoglobin A1c (HbA1c), total cholesterol, and low-density lipoprotein (LDL) cholesterol and increased high-density lipoprotein (HDL).^[11][12][2]

Lastly, the adaptogenic properties of tulsi have only been assessed in a few clinical trials. One randomized controlled trial found that tulsi reduced reaction time and error rates in tests measuring short-term memory and cognitive flexibility.^[13] Additionally, some studies have reported reduced symptoms of stress and anxiety and improved sleep, although the methods of assessment are questionable.^[14][15][16]

Tulsi appears to be relatively safe when used for up to 3 months, although thorough safety analyses have not been done. The most commonly reported side effects are nausea and diarrhea.^[2][17]

It’s not entirely clear whether tulsi is safe during pregnancy or when trying to get pregnant, but research in animal models suggests caution is warranted. Negative effects on the fertility of male (reduced sperm count) and female (reduced frequency of ovulation) animals have been observed. Additionally, when given during the first few weeks of gestation in female rats, tulsi leaf extract reduced the rate of implantation of the fertilized egg, reduced the number of live fetuses, and reduced fetal growth. However, it’s important to note that the dosages used in these studies ranged from 200 to 1,000 mg per kilogram of body weight, far exceeding dosages used in humans.^[18][19][20]

Tulsi contains many different bioactive compounds which could provide benefits through their individual and synergistic effects. Still, how tulsi works is not well understood, and more research is needed.

Many of the phytochemicals in tulsi are known to possess antioxidant, anti-inflammatory, and antimicrobial properties. The anti-inflammatory effects are thought to be due to the inhibition of the cyclooxygenase (COX) and lipoxygenase enzymes which are responsible for producing inflammatory compounds (e.g., leukotrienes, prostaglandins). Further, it’s been proposed that tulsi might modulate the stress response by influencing the HPA axis and produce antidiabetic effects by reducing glucose absorption and improving beta-cell function.^{[14][21][12][2]}