Herb library · Seaweed · Chlorella species (e.g. C. pyrenoidosa)
Chlorella
A freshwater green alga pressed into tablets and powders, sold for nutrition, weight and cholesterol. A 2026 review of 24 trials found small improvements in weight, cholesterol and insulin, but rated most of the evidence very low certainty.
Traditional use
A green alga rich in carotenes, protein, fiber, vitamins, minerals and chlorophyll. It is sold as tablets and powders, and Japanese researchers have studied it in pregnant women.
What studies show
- Limited
Weight, cholesterol and blood sugar: a 2026 meta-analysis of 24 trials found small reductions in body fat, BMI, LDL and total cholesterol, triglycerides, insulin resistance and CRP. The certainty was low for BMI and very low for most other results.
- Insufficient
Breast milk: small Japanese studies found chlorella taken during pregnancy changed some contents of breast milk (more carotenes and immune IgA, less dioxin). What that means for babies is not known.
Be careful of
Cautions
- NoteUsually well tolerated, but it can cause nausea, diarrhea, stomach cramps, gas and green stools.
- AllergyAllergic reactions, including asthma and anaphylaxis, have been reported in people taking chlorella and in workers making chlorella tablets. Skin reactions to sunlight (photosensitivity) have also occurred.
- InteractionChlorella is high in vitamin K and may make warfarin less effective.
- PregnancyLactMed considers chlorella probably acceptable during breastfeeding; green-colored breast milk has been reported.
- Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.
Sources
- Chlorella (LactMed) (opens in a new tab) · NIH · read September 25, 2026
- Beneficial effects of Chlorella species supplementation in the general population: a GRADE-assessed systematic review and dose-response meta-analysis (2026) (opens in a new tab) · NIH · read September 25, 2026
Reviewed September 25, 2026.