St. John's wort (Hypericum perforatum) contains hypericin and hyperforin as well as flavonoids such as quercetin. It is often recommended by midwives for postpartum depression.[1,2] Both hypericin and hyperforin are poorly excreted into breastmilk; no other components have been measured in milk. One study found a slightly increased frequency of colic, drowsiness and lethargy among breastfed infants whose mothers were taking St. John's wort, but none of the effects were severe or required treatment. Most reports have related to breastfeeding older infants, rather than during the first 2 months postpartum when infants are more susceptible to adverse reactions. Conflicting information exists on whether St. John's wort can reduce serum prolactin levels or the maternal milk supply, although some mothers in Turkey reportedly use it to increase their milk supply. Galactogogues should never replace evaluation and counseling on modifiable factors that affect milk production.[4,5] St. John's wort adversely interacts with many drugs by increasing their metabolism, and it can occasionally cause phototoxicity. Labeling of commercially available products in the United States is often deficient with respect to these known safety issues. Because there is little published experience with St. John's wort during breastfeeding, an alternate drug may be preferred, especially while nursing a newborn or preterm infant.
Dietary supplements do not require extensive pre-marketing approval from the U.S. Food and Drug Administration. Manufacturers are responsible to ensure the safety, but do not need to prove the safety and effectiveness of dietary supplements before they are marketed. Dietary supplements may contain multiple ingredients, and differences are often found between labeled and actual ingredients or their amounts. A manufacturer may contract with an independent organization to verify the quality of a product or its ingredients, but that does not certify the safety or effectiveness of a product. Because of the above issues, clinical testing results on one product may not be applicable to other products. More detailed information about dietary supplements is available elsewhere on the LactMed Web site.