Chlorella (Chlorella vulgaris)

Active Compounds

Chlorophyll a and b give chlorella its intensely green color; reported chlorophyll content varies with strain, growing conditions and processing. Ingested chlorophyll is extensively broken down in the gut, mostly to pheophytins, and animal studies suggest little of it is absorbed (Linus Pauling Institute). Chlorophyll and the semi-synthetic derivative chlorophyllin can form complexes with some dietary carcinogens such as aflatoxin-B1; small human studies, mostly of chlorophyllin rather than natural chlorophyll, found reduced aflatoxin uptake or biomarkers, but whether this lowers cancer risk is unknown (Linus Pauling Institute).

Chlorella Growth Factor (CGF) is a proprietary extract obtained by hot-water extraction of chlorella, consisting primarily of nucleotides, nucleic acids (RNA and DNA fragments), peptides, and polysaccharides from the cell interior (Rzeski & Rzeska, 2026). CGF is marketed based on observations that supplementing the growth medium of other organisms with CGF accelerates their growth rate. Direct evidence that CGF supplementation produces analogous growth-promoting effects in adult humans is lacking. A 2026 review describes CGF as a poorly standardized, nucleotide-dominant fraction rather than a true growth factor, and notes that controlled human studies of well-characterized CGF preparations are absent (Rzeski & Rzeska, 2026).

Cell wall: chlorella cells are enclosed in a rigid wall that human digestion cannot break down; a 2020 review describes it as cellulose and notes that most supplements are mechanically disrupted for this reason (Bito et al., 2020). Intact-cell-wall chlorella has significantly reduced bioavailability for intracellular nutrients including protein, vitamins, and chlorophyll. Commercial processing methods — including mechanical bead milling, spray drying with disruption, and high-pressure homogenization — physically rupture the cell wall to improve digestibility. Products labeled “broken cell wall” or “cell-cracked” chlorella are intended to address this limitation, though the efficacy of disruption varies between manufacturers.

Protein comprises roughly 50–70% of dry weight (about 59% on average across 13 commercial products), with all essential amino acids present in substantial amounts (Bito et al., 2020, a review with two co-authors from the supplement maker Sun Chlorella Corporation). Manufacturers of cell-wall-disrupted products report protein digestibility of about 75–85%, and an animal study found more than 80% of chlorella protein digestible (Bito et al., 2020).

Micronutrients include iron (around 100 mg/100 g dry weight in commercial products, though label values range widely), folate (about 0.3–3.6 mg/100 g), vitamin K, magnesium, other B vitamins, and vitamin C (Bito et al., 2020). Reported vitamin B12 content varies from under 0.1 to about 400 µg per 100 g between products and is much higher in C. pyrenoidosa than in C. vulgaris; some high-B12 products also contain inactive corrinoid analogues (Bito et al., 2020). Unlike spirulina, whose B12 is mostly inactive pseudo-B12 (Watanabe et al., 2014), some chlorella products appear to supply usable B12: in a small open-label study of 17 vegans and vegetarians with elevated methylmalonic acid, 9 g/day of C. pyrenoidosa for 60 days lowered serum methylmalonic acid by about 34% (Merchant et al., 2015). Because labels rarely distinguish active B12 from analogues, chlorella should not be relied on as a sole B12 source without blood-level monitoring.

Polysaccharides in chlorella’s hot-water extract stimulated mouse and cultured macrophages in laboratory studies; the main active fraction isolated from C. pyrenoidosa was a phosphorylated galactose-based polysaccharide, not a β-glucan of the kind studied in yeast and mushrooms (Suárez et al., 2010; Hsu et al., 2010). Human relevance is unestablished.

Nutritional Profile

Values approximate; vary by species, growing conditions, and processing method. Ranges are from label data for 13 commercial products compiled by Bito et al., 2020, a review two of whose co-authors work for Sun Chlorella Corporation.

Per 100 g dried powder:

Per 1 teaspoon (3 g) serving:

Chlorella vs Spirulina

Chlorella and spirulina are the two best-selling algae supplements and are often sold together, but they are different organisms. Chlorella is a green alga with a rigid cellulose cell wall; spirulina is a cyanobacterium that lacks one, so its protein is available without processing. Their B12, iron and vitamin K content also differ.

In practice, spirulina is the simpler protein source, while chlorella is the better candidate for B12 among algae, depending on the product. People taking warfarin have more reason to be careful with chlorella, given its vitamin K. Both carry the same contamination risks from pond cultivation, so third-party testing matters for either.

Evidence for Purported Benefits

Typical Use and Preparation

Photo: ja:User:NEON / User:NEON_ja, CC BY-SA 3.0, via Wikimedia Commons

Chlorella powder has a strong, grassy, somewhat sea-like flavor that is often blended into smoothies or diluted juices. Tablet and capsule forms are preferred by users who dislike the taste. Doses in the trials described above include 5 g per day (Kwak et al., 2012) and 9 g per day (Merchant et al., 2015).

Cell wall disruption is a prerequisite for meaningful intracellular nutrient delivery. When selecting powder products, verify that the manufacturer uses a validated disruption method (bead milling, pressure homogenization) rather than simply heat or spray drying, which may not fully disrupt the cell wall.

Product Selection Criteria

Cell wall processing: Confirm that the product uses mechanical cell wall disruption (bead milling or high-pressure homogenization), not heat or spray drying alone. The product label or manufacturer CoA should specify the processing method.

Third-party testing: Independent laboratory testing for microcystins (cyanotoxins), heavy metals (arsenic, lead, mercury, cadmium), and microbial contamination is the most critical quality indicator. Look for certificates of analysis from ISO 17025-accredited laboratories.

Origin: Chlorella was first produced and consumed commercially in Asia, mainly Japan (Bito et al., 2020). Country of origin alone does not establish purity; third-party contaminant testing is the more reliable indicator.

Form factor: Powder allows more flexible dosing than tablets. Liquid CGF extracts should specify CGF concentration in mg/mL.

Organic certification: USDA Organic or equivalent reduces pesticide residue risk but does not guarantee absence of environmental contaminants; in one analysis of 52 products, organic and conventional spirulina and chlorella did not differ in metal or drug-residue content (Sochacka et al., 2025).

Frequently Asked Questions