One relatively rare, adverse effect of use of the herb is photosensitivity. A theoretical concern, not yet tested, is that St John's wort may prevent metabolism of monoamines and contribute to hypertension. St John's wort as a dietary supplement, and, as such, it is not formally regulated. Purity of the extract and concentration of hypericin in the extract vary widely in the capsules sold commercially. Persons with moderate to severe depression requiring medication should remember that standard antidepressants have been well-tested for potency, purity, safety, and efficacy.
Herbal extracts sold in the U.S. are a gamble on all four counts.
Med Assoc, May 13, 1998. As you work with these new values it is important to remember that these numbers were set for professional use. They can be easily misinterpreted by those without professional nutrition training. For example the ULs are the maximum intakes that can be tolerated by an individual without adverse health effects. They are NOT desirable intakes and definitely not goals for intake.