Chlorella: A Complete Guide

Chlorella is a single-celled freshwater green alga that has been cultivated as a food supplement since the 1950s, originally in Japan and Taiwan. Open a tub of the powder and what hits you first is the colour: an almost absurdly deep green, like crushed moss. The smell is grassy, vegetal, faintly pond-like. That intensity comes from chlorophyll concentrations few other whole foods can match.

At 50 to 60 per cent protein by dry weight, with all essential amino acids, B-group vitamins, iron, and fibre, the nutrient profile is genuinely impressive for a microscopic organism. If you picked up a tub in a health shop and want to know whether it is worth the price, the short answer is that the nutrition is real.

The longer answer is that the supplement industry overpromises on chlorella in ways that deserve scrutiny.

Vendor disclosure: Phytality manufactures and sells a fermented chlorella product. We have written this guide from that perspective and have aimed for accuracy about both the strengths and limitations of chlorella as an ingredient.

What Chlorella Is and What It Is Not

Chlorella belongs to the green algae family and grows in freshwater. It is not seaweed, which is large enough to see and handle. It is not spirulina, which is a cyanobacterium from a different biological kingdom. And it is not marine phytoplankton, which grows in saltwater and delivers a different nutrient profile entirely.

These distinctions matter because you will find all four on the same shelf, often with similar marketing.

Two species dominate the supplement market: Chlorella vulgaris and Chlorella pyrenoidosa. Most published research uses C. vulgaris, and the nutritional profiles differ enough between species that your choice of product may not match the study being cited on its label. If the label does not name a species, that is a gap worth questioning.

For a deeper look at chlorella's biology, taxonomy, and how it fits among other algae supplements, our encyclopaedia article on chlorella covers the fundamentals in detail.

Chlorella Nutritional Profile: Protein, Chlorophyll, and Micronutrients

The protein figure is what catches your eye first. At 50 to 60 per cent by dry weight with all essential amino acids, chlorella looks like a standout. Then you do the arithmetic. At a typical supplement dose of 3 to 5 grams, you are consuming roughly 1.5 to 3 grams of actual protein. A tablespoon of porridge oats delivers more. The percentage is impressive; the portion is modest.

Where chlorella earns its place is the supporting nutrient matrix. It contains more chlorophyll per gram than any other commercially available food, alongside iron, zinc, B-group vitamins, beta-carotene, and dietary fibre. The iron is non-haem, which your body absorbs less efficiently than the haem iron in meat. Pairing your chlorella with a source of vitamin C, even a glass of orange juice, improves the absorption meaningfully.

Chlorella Nutrient Summary

For full nutritional data with per-serving calculations, see our chlorella nutrition facts breakdown.

The Chlorella B12 Question

You will see chlorella marketed as a vegan B12 source. The picture is more complicated than the labels suggest. Standard laboratory assays detect both true cobalamin, which your body can use, and pseudocobalamin, which it largely cannot. Not every manufacturer distinguishes between the two on the label. Some Chlorella species do appear to contain genuine B12, but the bioavailability question is not fully settled in the literature.

If you are vegan and considering chlorella specifically for B12, a dedicated B12 supplement remains cheaper and more reliable. Your GP can check your B12 status with a blood test, and we would recommend doing so before relying on any single food source.

Chlorella Health Benefits: What the Evidence Supports

The nutrients in chlorella are real. What you should be cautious about is extending those nutrients into therapeutic claims that the evidence does not support. We have reviewed the literature carefully, and the honest summary is that chlorella's strongest case rests on its verified nutritional composition rather than the disease-prevention claims that circulate online.

Chlorella Immune Support and Antioxidant Activity

Chlorella contains vitamin C and zinc, both of which contribute to the normal function of the immune system. That is an EFSA-authorised claim under Regulation EU 432/2012, at daily intakes of 80 mg and 10 mg respectively. Some preliminary studies have explored whether chlorella supplementation influences immune cell activity, but this research is early-stage and small-scale.

The chlorophyll and beta-carotene in chlorella have documented antioxidant activity in laboratory systems. No EFSA-authorised health claim exists for antioxidant compounds in microalgae specifically. If a product suggests chlorella prevents chronic disease through antioxidant activity, that claim has no regulatory basis.

Chlorella and Cholesterol: The Clinical Picture

A meta-analysis of randomised controlled trials (Panahi et al., 2016) found associations between chlorella supplementation and modest reductions in total cholesterol and LDL cholesterol, with the strongest effects in participants who had elevated baseline levels. The operative word is modest. Individual studies were small and short-term. If you have a cholesterol concern, this research does not replace statins or dietary changes your GP may recommend.

For a comprehensive look at where the research stands across all proposed benefits, see our chlorella benefits evidence review.

Chlorella and Detoxification Claims

This is the most oversold aspect of chlorella, so we will be direct. The claim is that chlorella binds to heavy metals like mercury, lead, and cadmium, helping your body excrete them. The theoretical basis involves chlorophyll's molecular structure, which resembles the heme group in haemoglobin, potentially enabling binding to certain metals.

Some laboratory studies have demonstrated metal-binding activity in cell cultures. Animal studies have shown mixed results. Robust human clinical trials confirming meaningful detoxification at realistic supplement doses are lacking. No EFSA-authorised health claim for detoxification exists for chlorella or any of its constituent compounds.

If your concern is genuine heavy metal toxicity, see your doctor. Chelation therapy exists for that purpose and chlorella is not a substitute. If your concern is general wellness, chlorella's verified nutrient density is the more honest selling point, and we think it is a strong enough one without the detox narrative.

Chlorella Side Effects and Safety

Chlorella is generally well-tolerated, but you should know what to expect before you start. Bloating, gas, and loose stools are the most commonly reported side effects, particularly in the first few days if you begin at a full dose. Starting with half a teaspoon and building up over a week usually resolves this. If you are prone to digestive sensitivity, take that ramp-up period seriously rather than pushing through.

Who Should Avoid Chlorella or Consult a GP First

Thyroid conditions. Chlorella contains iodine. If you have hyperthyroidism, excess iodine can worsen symptoms. Discuss supplementation with your GP before starting.

Anticoagulant medication. Chlorella contains vitamin K, which can interfere with blood thinners such as warfarin. If you take anticoagulants, your GP or pharmacist needs to know before you add chlorella to your intake.

Mould allergy. Some people with mould allergies react to chlorella. A small trial dose with a 24 to 48 hour wait is sensible before committing to a full regimen.

Pregnancy and breastfeeding. Insufficient safety data exists to recommend chlorella during pregnancy or breastfeeding. Unless your healthcare provider specifically advises it, avoid supplementation during these periods.

For a more detailed look at side effects with dosage guidance, see our chlorella side effects article.

How Chlorella Is Grown and Why It Matters to You

Not all chlorella is produced the same way, and the production method directly affects purity, contamination risk, and what ends up in the tub you buy. This is where your purchasing decision gets practical.

Open-Pond vs Closed Bioreactor Chlorella Production

Open ponds are the cheapest cultivation method. Chlorella grows outdoors in large, shallow pools exposed to whatever is in the surrounding air: dust, bacteria, agricultural run-off, heavy metals from local industry. If you are taking chlorella partly for its proposed heavy metal binding properties, the irony of consuming a contaminated product should give you pause.

Closed bioreactors use sealed glass or plastic tube systems with controlled light, temperature, and nutrient delivery. Contamination risk drops substantially. The product is cleaner. It also costs more to produce, which is reflected at the till. For a supplement you are taking daily, we consider the purity difference worth the price gap.

After harvesting, chlorella is separated from its growth medium by centrifugation or filtration, then dried. The next processing step determines how well you absorb it.

Fermented Chlorella vs Broken Cell Wall Chlorella

Chlorella has a tough cellulose cell wall that your digestive system struggles to break down without processing. Unprocessed chlorella passes through you with much of the nutrition intact but unavailable. Both broken cell wall and fermentation methods solve this, but the approach differs.

How Mechanical Cracking and Fermentation Compare

Broken cell wall (mechanical processing): The cell wall is physically cracked using pressure or milling. This does improve nutrient access. The trade-off is that the mechanical force can oxidise the lipids inside the cell, potentially reducing the nutritional value of the fats and certain vitamins in the final product.

Fermentation: A controlled fermentation process softens the cell wall without mechanical force. In our assessment, this approach better preserves lipid integrity because it avoids the oxidation that mechanical cracking can cause. Whether that difference matters to you depends on how much you are optimising and what you are willing to pay. For a deeper comparison, see our article on fermented vs pulverised chlorella.

How to Choose a Chlorella Supplement

If you are standing in a health shop or scrolling through an online store, three checks will separate a well-made chlorella product from one coasting on marketing.

Three Chlorella Label Checks That Matter

1. Species name. The label should identify Chlorella vulgaris or Chlorella pyrenoidosa. "Chlorella" without a species is a category, not a specification. Most published research uses C. vulgaris, so if you want your product to match the evidence base, that is the species to look for.

2. Cell wall processing. Look for "broken cell wall" or "fermented" on the label. If neither appears, you may be paying for nutrition your body cannot access. Unprocessed chlorella has significantly lower bioavailability.

3. Heavy metal testing. Chlorella bioaccumulates metals from its growing environment. A product grown in open ponds without batch-specific testing is a risk you do not need to take. Look for a certificate of analysis or a statement about independent heavy metal testing. If the manufacturer cannot produce one, consider why not.

Chlorella vs Spirulina: Which One Should You Take?

This is the comparison most people searching for a chlorella guide want answered. Neither is categorically better. They are different organisms with overlapping but distinct nutritional profiles, and the right choice depends on what gap you are filling.

Spirulina typically has slightly higher protein (55 to 70 per cent by dry weight versus chlorella's 50 to 60%) and contains phycocyanin, a unique blue pigment with documented antioxidant properties. Chlorella has more iron, more chlorophyll, and is the only one of the two with meaningful fibre content. Spirulina has a milder taste that some people find easier to tolerate.

In our assessment, if you want concentrated micronutrients with fibre and are comfortable with a strong taste, chlorella has the edge. If protein density and ease of use matter more, spirulina may suit you better. Taking both is a reasonable approach if your budget allows it. They complement rather than duplicate each other.

What Formulating Chlorella Taught Us

Fermentation changes the conversation about bioavailability. When we moved from mechanically cracked chlorella to a fermented process, the difference under microscopy was immediately visible. Mechanical cracking fractures cell walls but also exposes lipids to oxidation. Fermentation opens the cell more gently. The resulting powder has a different texture, a slightly less sharp taste, and in our assessment, better retention of heat-sensitive nutrients like folate.

Species selection is not interchangeable. We chose Chlorella vulgaris specifically because the published evidence base is overwhelmingly built on this species. Chlorella pyrenoidosa appears in older literature, but the taxonomy has been revised multiple times and some products labelled pyrenoidosa may actually be vulgaris strains.

If you are paying a premium for chlorella based on research, the species should match the studies.

Heavy metal testing is the line between responsible and reckless. Chlorella bioaccumulates metals from its growth medium. Every batch we produce is independently tested for lead, cadmium, arsenic, and mercury. The results go into a certificate of analysis that any customer can request.

We learned early that the cost of batch testing is trivial compared to the cost of selling a product you have not verified. Not every manufacturer reaches the same conclusion.

Chlorella Supplement Guide FAQ

How much chlorella should you take per day?

Most products recommend 3 to 10 grams daily. If you are new to chlorella, start at the lower end and increase over a week. Digestive discomfort is the most common reason people abandon it, and starting too high is almost always the cause. Our own fermented chlorella recommends 1.5 g per day, which reflects the lower-dose end appropriate for a concentrated fermented product.

Can you take chlorella if you are on blood thinners?

Chlorella contains vitamin K, which plays a role in blood clotting. If you take warfarin or another anticoagulant, adding chlorella can alter your INR levels. Speak to your GP or pharmacist before starting, and do not adjust your medication based on supplement intake without medical guidance.

Is chlorella safe during pregnancy?

There is insufficient safety data to recommend chlorella supplementation during pregnancy or breastfeeding. Unless your midwife or obstetrician specifically advises it, it is best to avoid it during these periods.

How do you mask the taste of chlorella powder?

Chlorella has a strong, earthy, slightly bitter flavour. Blending it into a smoothie with banana and a sharp fruit like pineapple or mango works well. Alternatively, capsule-form chlorella avoids the taste entirely. If you are the sort of person who gags at green juices, tablets may be your better option.

Can you take chlorella and spirulina together?

Yes. They provide different nutrients, with chlorella stronger on iron, chlorophyll, and fibre, and spirulina stronger on protein and phycocyanin. Taking both is nutritionally complementary, not redundant. The main consideration is total cost and whether you are already meeting those nutrient needs through your diet.

Does chlorella actually detoxify heavy metals?

In laboratory studies, chlorella shows metal-binding activity. In human bodies at supplement doses, the evidence is insufficient to support detoxification claims. No EFSA-authorised health claim exists for this. If you have confirmed heavy metal exposure, medical chelation therapy is the appropriate treatment, not a food supplement.

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Consult your GP before starting any supplement.

Methodology and Disclosure

Phytality manufactures and sells fermented chlorella and marine phytoplankton supplements. We have a direct commercial interest in chlorella as an ingredient. All nutritional figures are drawn from published peer-reviewed literature cited above. EFSA-authorised health claims for iron, vitamin C, and zinc are cited under Regulation EU 432/2012 with intake conditions stated.

The cholesterol meta-analysis reference is Panahi et al. (2016). Comparisons with spirulina reflect established compositional differences documented in published reviews. The Phytality Perspective box reflects our product specifications.

Last reviewed: March 2026. Next review due: March 2027.