Called the “king of herbs,” basil is particularly popular in Mediterranean and Asian cuisines. Its aromatic leaves add flavor and color to pastas, pizzas, curries, soups, sauces (think pesto) and salads, as well as chicken and fish dishes.
The basil you’re probably most familiar with is sweet basil (Ocimum basilicum), in the mint family. But there are many other kinds (varieties of this species or related species or hybrids) with such names as Thai basil, lemon basil, purple basil and cinnamon basil. All are used as culinary herbs but some have also been part of traditional Chinese and Indian medicine. In particular, holy basil (Ocimum tenuiflorum or Ocimum sanctum)— called tulsi in Hindi, meaning “incomparable one”—is considered a sacred Indian plant and is used to treat hypertension, respiratory disorders, diabetes, wounds and other conditions. Practitioners use the roots and leaves in tea and sometimes apply it topically.
Basil leaves contain essential oils, including limonene and eugenol, which have antioxidant properties. These aromatic compounds help defend plants against bacteria, fungi and insects, among other beneficial functions. In lab studies, basil extracts have been shown to inhibit the growth of bacteria like Salmonella and E. coli, as well as viruses, including hepatitis B and adenoviruses (which cause the common cold and other infections). The extracts also have anti-inflammatory, blood-sugar-lowering, immune-boosting and anti-cancer activity. One test-tube study found that, of all herbs tested, basil suppressed the growth of oral cancer cells best.
The chemical makeup of basil varies, however, depending on the variety and other factors, such as the soil and climate in which it grows. Basil is a source of potassium, vitamins C and K, calcium and iron—though to get significant amounts you’d have to eat cups of the herb. Purple basil is richest in anthocyanins, the antioxidant pigments that give many plants their rich color.
Unfortunately, studies in people are in short supply. Some preliminary research suggests that holy basil may lower blood sugar in people with diabetes, but the Natural Standard, which evaluates complementary and alternative therapies, gives it a C rating for that use, meaning that the evidence is unclear or conflicting. Meanwhile, a few studies have found increases in certain immune cells in people consuming basil (in capsules and teas), though it’s unknown if this would have any practical effects.
Basil is also touted as a traditional “stress buster.” In a 2012 study from India, holy basil, taken for six weeks, reduced symptoms of stress (such as forgetfulness and fatigue) more than a placebo. But “stress” is difficult to define, and for other “stress” symptoms the placebo was just as effective.
Bottom line: Given the scarcity of good studies, we can’t vouch for any health effects of basil. But we can vouch for its tastiness. Use basil in salads and sandwiches, and in soups, stir-fries and other dishes. Look for less-common types like holy basil (with its distinct anise aroma) or purple basil. If your regular market doesn’t have them, look in farmers’ markets and Asian grocery stores. You can also buy holy basil plants, seeds and teas on line. And if you can’t find fresh basil, dried basil is readily available— though the drying process greatly reduces the phytochemicals, not to mention flavor.