A new meta-analysis suggests spirulina—a blue-green algae extract—can improve body weight, cholesterol, and blood pressure in overweight and obese individuals. But before jumping on the supplement train, it’s worth digging into the evidence to see how strong the impact really is, how meaningful it is in practice, and whether spirulina makes sense as part of your routine.
Table of Contents
- What is Spirulina?
- Does the Hype Match the Evidence?
- Study Results: What Spirulina Actually Improves
- How Big Are the Benefits?
- How Strong is the Evidence?
- Should You Take Spirulina?
- Dosing and Safety
- Final Thoughts
- References
What is Spirulina?
Spirulina is a blue-green algae that naturally grows in lakes, ponds, and rivers in warm climates. It has been used for centuries as a food source—famously by the Aztecs—and later gained popularity for its antioxidant and anti-inflammatory properties. It even achieved notoriety as a dietary supplement used by NASA for astronauts on space missions [1].
Claims about spirulina’s nutritional power abound. One particularly bold claim is that “1 kg of spirulina has the nutritional value of 1,000 kg of fruits and vegetables.” By that logic, a 5 g serving would deliver the nutrition of 5 kg of produce. If that were true, we’d expect miraculous health benefits. So, does research live up to the hype?
Does the Hype Match the Evidence?
A 2025 meta-analysis explored spirulina’s effects on body composition and cardiovascular health markers in overweight and obese adults [2]. It pooled 23 randomized controlled trials with about 1,000 participants.
Why does this matter? Obesity promotes oxidative stress and chronic inflammation, which drive insulin resistance, hypertension, and elevated cholesterol [3]. If spirulina can counteract oxidative stress and inflammation, it could improve those health outcomes.
Study Results: What Spirulina Actually Improves
Without Exercise
When used without exercise, spirulina supplementation significantly:
- Reduced body weight
- Lowered total cholesterol
- Reduced triglycerides
- Lowered LDL cholesterol
- Decreased diastolic blood pressure
-
Increased HDL cholesterol [2]
With Exercise
When combined with exercise, spirulina produced additional benefits:
- HDL cholesterol rose further
-
LDL cholesterol dropped a bit more [2]
What It Didn’t Change
Spirulina did not significantly affect fasting blood sugar or insulin levels [2].
How Big Are the Benefits?
Statistical significance doesn’t always mean clinical importance. Let’s translate the numbers:
-
Body weight: Effect size −0.30, considered small. This equaled about 2.36 kg (5.2 lbs), or 2–3% of body weight [2]. Clinical guidelines usually consider 5% weight loss meaningful [4].
- LDL cholesterol: Effect size −0.71 (moderate), ≈ −12.44 mg/dL [2].
- Total cholesterol: Effect size −0.79, bordering on large.
- Triglycerides: Effect size −0.64, moderate.
- HDL cholesterol: Effect size +0.53, moderate.
- Diastolic blood pressure: Effect size −0.73, ≈ −2.6 mmHg [2].
Interpretation:
- The weight effect is small—not enough to be clinically meaningful on its own.
- Lipid and blood pressure changes are modest, but they do matter. For example, even a 2–3 mmHg reduction in blood pressure reduces cardiovascular risk.
How Strong is the Evidence?
Here’s the catch: the first meta-analysis rated most evidence as low or very low quality due to high heterogeneity (the studies varied widely in methods and outcomes) [2]. That means the true effect may be weaker than the pooled results suggest.
A Second Meta-Analysis for Perspective
A broader 2025 review of 35 studies and 1,523 participants found [5]:
- LDL cholesterol reduction: −7.69 mg/dL (smaller than the first study).
- Weight loss: −1.78 kg (3.9 lbs).
- Inflammation markers: significantly reduced.
- Evidence quality: mostly moderate; weight effect rated high.
Like the first analysis, it also noted high heterogeneity.
Should You Take Spirulina?
The evidence is intriguing but limited. The benefits are modest and the confidence is low, especially compared to other interventions.
Comparisons with Stronger Evidence
- DASH diet: Reduced LDL by 5.33 mg/dL across 22 high-quality studies with 3,500+ participants [6].
-
Soluble fiber supplements: Reduced LDL by 8.28 mg/dL across 181 trials with 14,000+ participants—very strong evidence [7].
Clearly, diets rich in whole foods, fruits, vegetables, lean proteins, and fiber deliver greater, more reliable benefits than spirulina supplements.
The transcript source also noted a personal stance: spirulina is used only as a natural coloring in their own “Sleep” supplement, not as a separate health supplement.
Dosing and Safety
If you still want to try spirulina, here’s what the first meta-analysis recommends [2]:
- Dose: 2–3 g/day powdered spirulina
-
Duration: 7–8 weeks for benefit; up to 24 weeks to sustain effects
Supplement Quality Matters
Contamination and mislabeling are real risks. ConsumerLab.com independently tests supplements: only 2 of 5 spirulina products passed their review.
(Note: the original source emphasized they have no affiliation with ConsumerLab.)
Final Thoughts
Spirulina can modestly reduce weight, cholesterol, and blood pressure, especially in overweight individuals. But the effects are small and the evidence quality is limited.
Compared to proven strategies like the DASH diet or fiber supplementation, spirulina doesn’t offer unique advantages.
That said, if you already take spirulina—or want to try it—it’s generally safe, may offer mild support for cardiometabolic health, and is best seen as a complement, not a replacement, to a healthy lifestyle.
References
1. https://pmc.ncbi.nlm.nih.gov/articles/PMC3136577/
2. https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1624982/full
3. https://pmc.ncbi.nlm.nih.gov/articles/PMC10178199/
4. https://pmc.ncbi.nlm.nih.gov/articles/PMC5497590/
5. https://www.sciencedirect.com/science/article/pii/S0965229925001189
6. https://www.sciencedirect.com/science/article/abs/pii/S093947532500211X
