In: Drugs and Lactation Database (LactMed®) [Internet]. Bethesda (MD): National Institute of Child Health and Human Development; 2006.


Chlorella sp. is a fresh-water green alga that contains various nutrients such as carotenes, protein, fiber, vitamins, minerals and chlorophyll. Taking Chlorella supplements during pregnancy may decrease dioxin content and increase the concentration of some carotenes and immunoglobulin A in breastmilk. Chlorella is usually well tolerated, but can cause nausea, diarrhea, abdominal cramping, flatulence, and green stools. Allergic reactions, including asthma and anaphylaxis, have been reported in people taking Chlorella, and in those preparing chlorella tablets. Photosensitivity reactions have also occurred following ingestion of Chlorella. The high vitamin K content of Chlorella may decrease warfarin effectiveness. Maternal Chlorella intake would not be expected to cause adverse effects in most breastfed infants and is probably acceptable during breastfeeding. Green breastmilk discoloration has been reported.

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.

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