Also known as: Chlorella vulgaris, Chlorella pyrenoidosa, Cracked cell wall chlorella, CGF
FoundationalEmerging evidence
A single-celled green algae grown as a food, high in protein and chlorophyll. Its rigid cell wall has to be broken before you can digest it, and that processing step decides whether a product works.
Typical dose
2.0–6.0 g per day
With food, split across the day
What it is
Chlorella is a freshwater green algae, cultivated commercially in ponds and tanks. It is around 50 to 60 per cent protein by dry weight and intensely green from its chlorophyll content.
The critical difference from spirulina is the cell wall. Chlorella has a tough cellulose wall that humans cannot digest, so the material must be mechanically cracked or pulverised before any of the contents become available.
Any product not stating that the cell wall has been broken is worth avoiding entirely, because the nutrients will pass straight through. Look for cracked cell wall or broken cell wall on the label.
How it works
Much of what chlorella does is straightforwardly nutritional. It supplies protein, iron, magnesium, carotenoids and chlorophyll in a concentrated form.
The cell wall material that makes it hard to digest also binds certain compounds in the gut, which is the basis for research on it affecting the absorption of environmental contaminants. That work is largely preclinical.
On vitamin B12, the position is less settled than for spirulina. Some chlorella species appear to contain forms with genuine activity, though the amount and consistency vary enough that relying on it as a sole B12 source on a plant-based diet would be unwise.
What the evidence shows
Human research is limited. Small trials have reported improvements in lipid markers and in some measures of oxidative stress, with modest effect sizes.
There is a small body of work on immune measures and on exercise-related outcomes, generally preliminary.
The reasonable assessment is a nutrient-dense whole food with a thin supplement evidence base. As a concentrated source of iron, protein and carotenoids for someone eating a restricted diet it has a clear role, and the broader claims made for it go well beyond what has been shown.
Dosing
Typical intake is 2 to 6 g daily, taken with food. Trials have used doses across this range.
Buy cracked cell wall material and nothing else. This single specification matters more than dose, brand or price.
Sourcing is the second consideration. Algae concentrate what is in their growing water, so heavy metal testing is worth insisting on. The taste is strong and distinctly pond-like, which is why tablets are more popular than powder.
Not applicable; effects on markers accrue over weeks
Timing
With food, split across the day
Competition status
Permitted — not on the WADA Prohibited List
Category
Foundational
Safety and side effects
Chlorella is generally well tolerated. Digestive effects are common in the first week, including gas, bloating and green discolouration of stools, all of which are harmless.
Heavy metal accumulation is a genuine consideration given how algae grow. Third-party testing is worth requiring rather than assuming.
Chlorella is relatively high in vitamin K, which is worth mentioning to your prescriber if you take anything affecting blood clotting. Speak to your doctor before use if your immune system is being managed.
Who should avoid it
Buy only from producers who publish heavy metal testing. Mention it to your prescriber if you take anything affecting blood clotting, given the vitamin K content. Speak to your doctor before use if your immune system is being managed. Avoid if sensitive to algae or moulds. Not a reliable sole source of B12.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
