Chlorella is a single-celled green alga that grows in fresh water and has been sold as a dietary supplement around the world for decades. It is often described as a superfood that does everything from boosting immunity to "detoxing" the body. Some of those claims have reasonable support, and some do not. Here is what the research shows.
What is chlorella?
Chlorella is a microscopic alga, usually sold as tablets or a bright green powder. It is nutrient-dense: a 2020 review in Nutrients notes that chlorella products contain a range of vitamins and minerals, including vitamins D and B12, which are rarely found in plant foods, and more folate and iron than other plant-derived foods.
The B12 content varies between species and products, so chlorella should not be relied on as a vegan's only B12 source. Chlorella also has a tough cell wall, which is why many products are labeled "broken cell wall."
What are the potential benefits of chlorella?
Cholesterol and blood pressure
This is the best-studied area, and the results are mixed. A 2018 meta-analysis of 19 randomized trials found chlorella lowered total cholesterol by about 9 mg/dL, LDL cholesterol by about 8 mg/dL and systolic blood pressure by about 4.5 mmHg, with the clearest effects at more than 4 g a day for at least eight weeks. A 2025 meta-analysis of a smaller set of trials, however, found a neutral effect on blood pressure and blood lipids. The honest summary: chlorella may modestly support healthy cholesterol and blood pressure levels, but it is no substitute for diet, exercise or any treatment your doctor recommends.
Blood sugar
The 2018 meta-analysis also found a small reduction in fasting blood glucose, about 4 mg/dL. Effects on triglycerides, HDL cholesterol and body mass index were not significant.
Immune function
In an eight-week randomized, placebo-controlled trial in healthy adults, 5 g of chlorella a day increased the activity of natural killer cells, a type of white blood cell, along with several immune-signaling molecules. It was a small study, but it suggests chlorella may support normal immune function.
Antioxidants
The 2020 review also describes antioxidant activity from chlorella's mix of nutrients and plant compounds, though which compounds are responsible is still not well understood. Learn more in what are antioxidants?
Does chlorella detox heavy metals or fight cancer?
These are the boldest claims made for chlorella, and the evidence in people is not there to support them. Interest in chlorella binding heavy metals and in its effects on cancer cells comes largely from laboratory and animal research. We could not find good evidence that chlorella removes heavy metals from the body or prevents or treats cancer in humans, so we do not make those claims. If you are being treated for cancer, talk to your care team before taking any supplement.
Is chlorella safe, and how do you take it?
Chlorella is sold as tablets and powders; the trials above used a few grams a day. Start with the dose on the label and give it several weeks before judging the effect. As with any supplement, check with your doctor first if you are pregnant or breastfeeding, take a blood thinner or other regular medication, or have an immune condition.
Choose a product that is independently tested for contaminants such as heavy metals. If you would rather get a broad mix of greens in one scoop, our guide to what is in a greens supplement explains what to look for, and Easy Being Green combines more than 20 organic greens and superfoods from land and sea, tested under our 5 Nation Standard.
