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Chlorella: what it is, what studies show, and what to buy

By the Life in Good Form editors. Updated 2026-10-15.

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What chlorella is

Chlorella is a green, single-celled microalga. NOW Foods describes it as containing naturally occurring chlorophyll and other plant nutrients. Its cell wall is broken down mechanically in many products to aid digestibility, which is why labels say broken cell wall or cracked cell wall.

Chlorella is often sold with spirulina, but they are different organisms: spirulina is Arthrospira platensis, while chlorella supplements use Chlorella species such as Chlorella vulgaris. See our spirulina guide for that product.

What the research shows

Weight and metabolism. A 2026 GRADE-assessed meta-analysis in Nutrition and Diabetes pooled 24 studies and found chlorella reduced body weight by about 1.3 kg, BMI by 0.3, body fat by 0.7 percentage points, LDL cholesterol by about 6 mg/dl and total cholesterol by about 8 mg/dl. It also reported lower insulin, triglycerides, a marker of inflammation (hs-CRP), a marker of oxidative stress (malondialdehyde) and leptin, and higher levels of the antioxidant enzyme catalase. It rated the evidence for BMI as low and for most other outcomes as very low, so the authors urged caution.

Blood pressure and blood fats. A 2025 meta-analysis in Nutrients reviewed 12 randomized chlorella studies and found a neutral effect on blood pressure and blood fats. It found a small diastolic drop with spirulina instead.

Iron. A 2025 systematic review of 32 studies, only 7 in humans, found spirulina and chlorella improved hemoglobin, ferritin and red blood cell counts and reported no significant adverse effects, but called for longer human trials. In those studies, chlorella also raised antioxidant enzymes and both algae lowered hepcidin, a hormone that limits iron absorption during inflammation. The review notes iron deficiency anemia affects over two billion people worldwide and that standard iron pills are often poorly tolerated.

Safety

• Stomach upset. NOW Foods says chlorella may cause digestive discomfort in sensitive people.
• Few reported harms in studies. The 2025 iron review reported no significant adverse effects or organ toxicity in its included studies.
• Uncertain benefits. With very low certainty for most outcomes, do not use chlorella in place of treatment for high cholesterol, diabetes or anemia.
• Medicines and conditions. Ask your provider before adding any supplement if you take medicines, have a medical condition, or are pregnant or nursing.

Tablets or powder?

• Tablets. NOW Foods' Organic Chlorella gives 3 g (3,000 mg) of broken cell wall chlorella per 6 tablets, with 2 g of protein, taken daily.
• Powder. Lets you mix gram amounts into smoothies; measure carefully.
• Spirulina and chlorella combos. Convenient, but you get less of each per serving.
• Greens blends. Many greens powders list chlorella among many ingredients; check how much is in each serving.

How to choose chlorella

• Broken cell wall. Look for broken or cracked cell wall on the label, as NOW Foods describes for digestibility.
• Organic and tested. Prefer USDA Organic and third-party testing for contaminants and heavy metals.
• Pure product. Choose chlorella alone if you want to see how you respond.
• Start with the label amount. Begin slowly if your stomach is sensitive.
• Realistic expectations. Study effects were small and uncertain.

Who should check with a doctor

Talk with your doctor before relying on chlorella if you have iron deficiency anemia, high cholesterol, diabetes or a digestive condition. Anemia needs a diagnosis and a treatment plan, and the iron research on chlorella is still early, with most studies in animals.

What to look for when you buy

Questions people ask

What is chlorella good for?

A 2026 meta-analysis found small drops in weight, body fat and cholesterol, but the certainty of evidence was very low to low.

What is broken cell wall chlorella?

Chlorella whose tough cell wall has been broken mechanically to aid digestibility, according to NOW Foods.

Is chlorella the same as spirulina?

No. They are different microalgae, often sold together. Spirulina is Arthrospira platensis; chlorella is a Chlorella species.

Does chlorella help iron levels?

A 2025 review suggests it may, but only 7 of the 32 studies were in humans. Anemia needs medical care.

How much chlorella should I take?

Follow the label. NOW Foods directs 6 tablets (3 g) daily.

Sources

• Beneficial effects of Chlorella species supplementation in the general population: a GRADE-assessed systematic review and dose-response meta-analysis (pmc.ncbi.nlm.nih.gov), Nutrition and Diabetes (PMC13631250)
• The Role of Chlorella and Spirulina as Adjuvants of Cardiovascular Risk Factor Control: A Systematic Review and Meta-Analysis of Randomised Controlled Trials (pmc.ncbi.nlm.nih.gov), Nutrients (PMC11945647)
• Arthrospira platensis and Chlorella vulgaris Consumption on Iron Status: A Systematic Review of In Vivo Studies (pmc.ncbi.nlm.nih.gov), Molecular Nutrition and Food Research (PMC12700048)
• Chlorella 500 mg Organic Tablets (www.nowfoods.com/products/supplements/chlorella-500-mg-organic-tablets), NOW Foods

Sources checked 2026-10-15.