Basil (Ocimum basilicum) contains linalool, 1,8 cineole (eucalyptol), methylchavicol, methylcinnamate and an essential oil with high estragole content. Estragole might be a procarcinogen. Basil is a purported galactogogue[1,2] but has also been used to decrease breastmilk oversupply in Persian traditional medicine.[3] No scientifically valid clinical trials support either of these uses. Galactogogues should never replace evaluation and counseling on modifiable factors that affect milk production.[4,5] No data exist on the excretion of any components of basil into breastmilk or on the safety and efficacy of basil in nursing mothers or infants. Basil is "generally recognized as safe" (GRAS) as a food by the U.S. Food and Drug Administration. Basil appears to be safe during breastfeeding in the amounts found in foods, but many sources recommend that medicinal doses of basil not be used during lactation because of its estragole content and lack of safety information.[6]
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.