Chlorella
Summary
Chlorella is a single-celled green alga sold as tablets. Meta-analyses of small trials found modest falls in total and LDL cholesterol (about 7–9 mg/dL; grade B) and in systolic blood pressure, but evidence certainty is very low and an 8-week diabetes trial found no effect. Case reports link chlorella to reduced warfarin effect and sun sensitivity.
Key facts
- Total cholesterol −9.1 mg/dL and LDL −8.3 mg/dL versus control across 19 RCTs (797 people)[1]
- Systolic −4.5 mm Hg and diastolic −1.6 mm Hg in the same meta-analysis[1]
- A 2026 GRADE-assessed review rated most chlorella outcomes very low certainty[3]
- Only 2 of 10 trials in a 2022 review checked chlorella content, purity or contamination[2]
- 5 graded human outcomes on this page
- October 13, 2026
How it works
ProposedTrial authors propose that chlorella reduces intestinal absorption of dietary and bile cholesterol; in a 4-week trial, the fall in serum lipids tracked a rise in serum carotenoids such as lutein and α-carotene, which chlorella supplies. The mechanism has not been confirmed directly in humans.[4][5]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Cholesterol | Grade B | Improved | Meta-analysis of 19 trials · n = 797 · 2018 | 4 rows |
| Blood sugar | Grade D | No effect | RCT · n = 84 · 2021 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Cholesterol, blood pressure and fasting glucose | Improved | Grade B | Meta-analysis · n = 797 · 2018 Adults of varied health status (19 RCTs) Form: Chlorella (various species and products) · Dose: Varied; effects clearer above 4 g/day in subgroup analysis · Duration: Varied; effects clearer at 8 weeks or longer Total cholesterol fell 9.1 mg/dL, LDL 8.3 mg/dL, systolic BP 4.5 mm Hg, diastolic BP 1.6 mm Hg and fasting glucose 4.2 mg/dL; triglycerides, HDL and BMI did not change. | 29037431 (opens PubMed)Source [1] |
| Blood lipids (Chlorella vulgaris) | Improved | Grade B | Meta-analysis · n = 539 · 2022 Adults (10 RCTs) Form: Chlorella vulgaris · Dose: Varied; LDL effect seen at doses up to 1,500 mg/day in dose-response analysis · Duration: Varied Total cholesterol fell 7.5 mg/dL and LDL 7.7 mg/dL; triglycerides and HDL did not change. Only 4 trials had low risk of bias. | 35331862 (opens PubMed)Source [2] |
| Serum lipids in mildly high cholesterol | Improved | Grade C | RCT · n = 63 · 2014 Adults with mild hypercholesterolaemia Form: Chlorella · Dose: 5 g/day · Duration: 4 weeks (after 2-week lead-in) Versus placebo, total cholesterol (−1.6% vs 0.03%) and triglycerides (−10.3% vs +11.9%) fell, with lower VLDL and apolipoprotein B and large rises in serum lutein/zeaxanthin and α-carotene. | 24920270 (opens PubMed)Source [4] |
| Serum cholesterol during a dietary cholesterol challenge | Improved | Grade C | RCT · n = 34 · 2016 Healthy adults eating three eggs (510 mg cholesterol) daily Form: Chlorella · Dose: 5 g/day · Duration: 4 weeks Total cholesterol rose 3.5% versus 9.8% on placebo and LDL 1.7% versus 14.3%. | 27177615 (opens PubMed)Source [5] |
| Glycaemic control, lipids and body measures in type 2 diabetes | No effect | Grade D | RCT · n = 84 · 2021 Adults with type 2 diabetes Form: Chlorella vulgaris · Dose: 1,500 mg/day · Duration: 8 weeks No change in fasting glucose, HbA1c, insulin, insulin resistance, lipids or anthropometric measures versus placebo. | 33532874 (opens PubMed)Source [6] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Chlorella tablets or powder (C. vulgaris, C. pyrenoidosa) | Varies[2] | Whole-alga product; serum lutein/zeaxanthin and α-carotene rose sharply on 5 g/day, showing its carotenoids are absorbed.[4] | No adverse-event differences reported in the cited trial abstracts; case reports describe sun-induced skin reactions and reduced warfarin effect.[4][8][7] | Cholesterol, blood pressure and blood sugar (1.5–5 g/day) |
Studied doses
Doses studied in human trials ranged from 1,500 mg/day to 5 g/day for 4 to 8 weeks in the individual trials cited here; meta-analysis subgroups found clearer lipid and blood-pressure effects above 4 g/day and at 8 weeks or longer.[6][4][5][1]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- WarfarinCase reportIn a case report, a man stable on warfarin lost anticoagulant control after starting chlorella; the authors attributed it to chlorella's vitamin K content.[7]
Who should be careful
- Warfarin users
- A case report describes warfarin becoming less effective after chlorella was started; vitamin K content is the proposed cause.[7]
- Sun sensitivity
- Five people developed swelling and purple-red lesions on sun-exposed skin after taking chlorella tablets; pheophorbide-a in the tablets was identified as the photosensitizer.[8]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
How to read the label
- Contamination testingMost trials did not verify chlorella content, purity or contamination, so third-party testing on the label matters.[2]
- Label dose vs studied doseIndividual trials used 1.5–5 g/day; a few 200–500 mg tablets a day falls well below this.[6][4]
- SpeciesReviews pooled several species; one 2022 review limited to Chlorella vulgaris found similar LDL effects.[1][2]
Cost per studied dose, without the sales pitch
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Cost per studied dose
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Frequently asked questions
Does chlorella lower cholesterol?
Modestly. Meta-analyses of small trials found total and LDL cholesterol 7–9 mg/dL lower than control, with very low certainty.[1][2][3]
Does chlorella lower blood pressure?
A 2018 meta-analysis found systolic pressure 4.5 mm Hg and diastolic 1.6 mm Hg lower, with clearer effects at higher doses and in people with hypertension.[1]
Does chlorella help blood sugar?
Pooled data showed a small fasting-glucose fall, but an 8-week trial of 1.5 g/day in type 2 diabetes found no change.[1][6]
Is chlorella the same as chlorophyll?
No. Chlorella is a whole single-celled alga; chlorophyll supplements are a separate product with their own page and evidence.[5]
Can chlorella interact with warfarin?
A case report describes warfarin losing effect after chlorella was started, attributed to its vitamin K content.[7]
What are the side effects of chlorella?
Trials reported few problems, but case reports describe sun-induced skin reactions linked to pheophorbide-a in tablets.[8]
Sources
- [1]Effect of Chlorella supplementation on cardiovascular risk factors: A meta-analysis of randomized controlled trials.. Clin Nutr, 2018. meta-analysis
- [2]Effect of supplementation with Chlorella vulgaris on lipid profile in adults: A systematic review and dose-response meta-analysis of randomized controlled trials.. Complement Ther Med, 2022. meta-analysis
- [3]Beneficial effects of Chlorella species supplementation in the general population: a GRADE-assessed systematic review and dose-response meta-analysis.. Nutr Diabetes, 2026. meta-analysis
- [4]Impact of daily Chlorella consumption on serum lipid and carotenoid profiles in mildly hypercholesterolemic adults: a double-blinded, randomized, placebo-controlled study.. Nutr J, 2014. RCT
- [5]A dietary cholesterol challenge study to assess Chlorella supplementation in maintaining healthy lipid levels in adults: a double-blinded, randomized, placebo-controlled study.. Nutr J, 2016. RCT
- [6]The effects of Chlorella supplementation on glycemic control, lipid profile and anthropometric measures on patients with type 2 diabetes mellitus.. Eur J Nutr, 2021. RCT
- [7][Warfarin therapy and chlorella].. Rinsho Shinkeigaku, 1995. review
- [8]Chlorella photosensitization. New phytophotodermatosis.. Int J Dermatol, 1984. review
What changed
- Strict second-pass self-review (no separate reviewer could be dispatched for this batch): all 8 PMIDs re-verified by NCBI esummary (titles and years match the record) and efetch checked for retraction, expression-of-concern and erratum flags (none flagged); every evidence row, key fact, form, dose, label line, FAQ and insight re-read against its abstract, and against PMC full text where the dose or count lives. Fixes: removed unsourced chlorophyllin and prescription-drug comparisons; trial form wording matched to the abstract. Page set indexable.
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year from the record) and abstracts read for each cited row. The 2026 GRADE review is cited for certainty only, because its abstract does not give a pooled participant count. No NIH ODS or NCCIH fact sheet covers chlorella.