St. John’s wort (SJW) is a widely known, non-prescription dietary supplement with use dating back to ancient Greece.
SJW is the common name for a flowering shrub native to Europe, Hypercium perforatum, also known as Klamath weed or goat weed. The name originates from when its yellow flowers bloom in late June, around St. John the Baptist’s Feast Day. “Wort” is an Old English word for a plant or herb used as food or medicinally.
The flowers and leaves of SJW contain bioactive ingredients hyperforin and hypericin that may affect neurotransmitters in the body. Extracts are available in the United States as tablets, liquids, teas and topical preparations.
Although not fully supported by scientific research, folk and traditional medicine utilizes SJW for conditions including insomnia, irritable bowel syndrome, wound healing, and menopausal symptoms. It is most commonly studied for mild to moderate depression as an alternative to antidepressants.
A 2008 Cochrane review of 29 clinical trials concluded that SJW was superior to placebo in patients with major depression and was similarly effective as standard antidepressants with fewer side-effects. Despite this, high-quality clinical data supporting the effectiveness as a monotherapy for depression is lacking. It is not yet considered a replacement for more studied treatments and proper medical consultation.
SJW is generally considered safe when used orally with no significant side effects. While usually minor and uncommon, some reported side effects include upset stomach, agitation, headache, fatigue, dizziness, sensitivity to sunlight, and dry mouth. SJW is a stimulant and may worsen feelings of anxiety in some individuals.
SJW interacts with many prescription medications through induction of the cytochrome P450 enzymes, resulting in altered drug effectiveness and potentially severe side effects when taken with oral contraceptives, certain chemotherapy drugs, statins, anticoagulants, or antidepressants.
Interactions with SJW and certain antidepressants may lead to an accumulation of high levels of serotonin, a brain chemical targeted by antidepressants. SJW may also limit absorption of iron and other minerals.
As with any new diet or supplement regimen, please consult with your physician to discuss if SJW is appropriate for you.
Environmental Nutrition is the award-winning independent newsletter written by nutrition experts dedicated to providing readers up-to-date, accurate information about health and nutrition.