Short answer: Both lowered cholesterol and blood pressure modestly in meta-analyses of small trials, and no trial compared them. Spirulina lowered systolic pressure about 4.4 mmHg;1 chlorella lowered it about 4.5 mmHg and LDL about 8 mg/dL.2 A US Pharmacopeia committee gave spirulina its top safety class.3
| Spirulina | Chlorella | |
|---|---|---|
| Cholesterol | Lower LDL, total cholesterol and triglycerides; higher HDL (20 trials, 1,076 people)4 | Total cholesterol down about 9 mg/dL, LDL about 8 mg/dL (19 trials, 797 people)2 |
| Blood pressure | Systolic down 4.4, diastolic 2.8 mmHg (moderate certainty)1 | Systolic down 4.5, diastolic 1.6 mmHg2 |
| Triglycerides | Lower4 | No significant change2 |
| Weight | Not covered in the sources checked | About 1.5 kg lower in a 2026 meta-analysis of 33 studies5 |
| Amounts in trials | Varied by trial4 | Effects seen above 4 g a day for 8 weeks or more2 |
| Safety review | USP Class A safety rating after reviewing 31 adverse event reports3 | Not covered in the sources checked |
Spirulina: a 2023 meta-analysis of 20 trials found lower LDL, total cholesterol and triglycerides and higher HDL.4 A 2025 meta-analysis found systolic blood pressure about 4.4 mmHg lower and diastolic 2.8 mmHg lower, with moderate-certainty evidence, and said more high-quality trials are needed.1
Chlorella: a 2018 meta-analysis of 19 trials found total cholesterol down 9.09 mg/dL, LDL down 8.32 mg/dL, systolic pressure down 4.51 mmHg and fasting blood sugar slightly lower, with no change in triglycerides, HDL or BMI.2 A 2026 meta-analysis of 33 studies found small drops in weight, body fat and LDL and said longer studies are needed.5
Both pooled small trials of different products, so the numbers are not directly comparable. These are study protocols, not personalized advice; confirm any dosing with your prescriber.
A US Pharmacopeia expert committee reviewed human trials, animal studies and 31 adverse event reports and gave Spirulina maxima and S. platensis a Class A safety rating.3 The chlorella sources here do not describe side effects in detail.
If you take blood pressure or cholesterol medicine, tell your prescriber before adding either. More detail: the Spirulina and Chlorella guides.