General Description
St. John's wort is a perennial shrub that grows wild in many parts
of the world, including North America and Europe. Flowering in July
and August, St. John's wort bears bright yellow blossoms that turn
red when bruised. The leaves and flowers are used for health purposes.
Health applications
History and traditional use
St. John's wort has a long history of folk use. In ancient Greece,
the herb was used to treat a variety of ailments, from back pains
to snake bites. Its genus name, Hypericum, is derived from a Greek
word meaning "over an image," reflecting the belief that the flowers
had the power to drive away evil spirits. Legends of the herb's
magical powers persisted in Medieval Europe, where the herb was
associated with St. John the Baptist, and its leaves were said to
bleed on the anniversary of his beheading. The herb is still popular
in much of Europe, where it is used topically to promote wound healing,
and internally to treat mild depression.
Chemical composition
The chief active components in St. John's wort are hypericin and
pseudohypericin, although other constituents such as xanthones,
hyperforin, and flavonoids may also exert biological activity.
St. John's wort and depression
St. John's wort is most commonly used for depression, and most
research on the herb has focused on this application. Studies
on the short-term treatment of mild to moderate depression have
shown St. John's wort to be more effective than placebo and as
effective as many prescription medications in reducing symptoms.
1-3 Although the herb's mechanism of action
is still the subject of debate, research indicates it may inhibit
the brain's re-uptake of certain neurotransmitters like serotonin,4
and increase some aspects of dopamine function.5
Dosage/Toxicity
The German Commission E Monograph recommends a daily dose of 2
to 4 grams of dried whole herb, or 0.2 to 1 mg total hypericin
in other formulations.6 Many herbalists recommend
extracts standardized to 0.3% hypericin content, because that
is the concentration used in most research. The standard recommendation
for these extracts is 300 mg three times daily with meals.7
St. John's wort is very well tolerated, with an incidence of adverse
side effects similar to that of placebo. The most common adverse
effects are gastrointestinal symptoms, dizziness/confusion, and
tiredness. In rare cases, it may cause increased sensitivity to
sunlight.8 Because St. John's wort may interact
with antidepressant medications or interfere with the action of
drugs such as protease inhibitors, contraceptives, transplant
rejection drugs, heart disease medications, cancer therapies,
and others, people who are taking prescription medications should
consult a knowledgeable physician or pharmacist before taking
St. John's wort. |
