Chlorella is a single-celled algae that grows in fresh water. It is extremely small — about the size of a human red blood cell. In 1890, the Dutch biologist Martinus Beijerinck was the first to describe common chlorella (Chlorella vulgaris) — it was one of the first microalgae found to have a well-defined cell nucleus.
What draws the most attention to chlorella is how fast it reproduces. With enough sunlight and nutrients, one chlorella cell can divide into about four new cells in a single day. Because it grows so fast and is high in protein, after the Second World War many countries seriously studied using it as a food supply for people. It became especially popular in places like Japan and Taiwan, and it is still a common health food today.
Why do chlorella tablets usually say “broken cell wall”?
This is something the old article did not mention, yet it is the most practical point when you are buying. Chlorella’s cell wall is made of cellulose and is very tough; human digestive enzymes cannot break it down. If the cell wall is not broken open first, most of the nutrients simply cannot be absorbed. That is why most chlorella products on the market are mechanically processed to break the cell wall first, and the label often says “broken cell wall” chlorella. It is worth looking for that line when you buy.
What is in chlorella?
By dry weight, chlorella is about 50–60% protein, and it contains all the essential amino acids. It also contains:
- Chlorophyll (about 1–3% of dry weight) — the source of its deep green colour;
- Carotenoids such as beta-carotene, and lutein;
- Folate, and minerals such as iron, magnesium and potassium;
- Vitamin K, and small amounts of vitamins C and E;
- A substance called “Chlorella Growth Factor” (CGF) — a complex of nucleic acids (DNA, RNA) and amino acids from the chlorella cell nucleus.
One point is worth reminding vegetarians about: although chlorella is often promoted as a plant source of vitamin B12, part of the B12 it contains is an analogue form that the human body cannot use, so you cannot rely on chlorella alone for B12.
The benefits people used to claim — how do they look today?
The old article listed many benefits: boosting immunity, detoxing, fighting cancer, anti-aging, weight loss, balancing an acidic body, and so on. Judged by today’s evidence standards, some of those claims need correcting:
Immunity. In laboratory and animal studies, chlorella’s polysaccharides can indeed affect the activity of immune cells, and a few small human studies have seen changes in some immune markers. But that does not mean chlorella can prevent cancer, treat cancer, or prevent infections — there is currently no such human evidence.
Detox. In water and in test-tube experiments, chlorella can bind heavy metals, which is exactly why it is used to purify wastewater. But “binding in water” is not the same as “detoxing inside the human body”. The claim that chlorella can remove accumulated pesticides, lead, mercury and the like from the body currently lacks reliable human evidence. There is a point that deserves more attention, and it is the reverse: precisely because algae absorb substances from their water, if the growing water is polluted, the product itself may carry heavy metals. So when buying, a third-party-tested product from a clear source matters more than any “detox” advertising.
Acid–alkaline body theory. The old article said eating too much meat makes the blood acidic, and that chlorella can neutralize it. In fact, modern medicine knows this clearly: the acidity of human blood is tightly controlled by the lungs and kidneys between pH 7.35 and 7.45, and food cannot change it in any meaningful way. Eating more plant foods is good for health for other reasons — not because it changes the blood’s pH.
Weight. The old article once suggested replacing snacks with a set number of tablets in order to lose weight. That kind of instruction has been removed in the new version — there is currently no reliable evidence that chlorella causes weight loss, and a product should never be used in place of proper meals, or in place of adjusting snacking habits.
What does the newest research say?
A systematic review and meta-analysis published in 2025 (in the journal Nutrients) gathered 12 randomized controlled trials of chlorella. The results showed that, overall, chlorella had no significant effect on blood pressure or blood lipids (cholesterol, triglycerides). That is a long way from the old article’s promotion, but it is the most complete summary of the evidence we have. There are also a few small trials in fatty-liver patients (mainly from Iran, small in size and short in length) reporting improvements in liver enzymes and blood sugar, but the trials are too small to rely on.
In short: chlorella is a nutrient-rich food, and as a supplement to the everyday diet it is fine — but it is not a medicine, and it cannot replace treatment.
Safety and cautions
Chlorella is generally well tolerated. The most common side effects are digestive discomfort — bloating, gas, loose stool or mild nausea — usually appearing in the first one to two weeks of use; starting with a small amount and taking it with food can ease this. People who should check with a doctor or pharmacist before using it include:
- People taking the blood thinner warfarin: chlorella contains vitamin K, which may reduce warfarin’s effect — case reports exist; also, while taking warfarin, do not start or stop chlorella on your own;
- People with immune-system conditions, or taking immunosuppressant drugs: chlorella may affect immune activity;
- People with thyroid problems, or sensitivity to iodine: chlorella contains iodine;
- People allergic to algae or mould, or who are pregnant or breastfeeding: safety information is not sufficient — consult a doctor first.
In Canada, choosing products that carry a Natural Product Number (NPN) and have been third-party tested is a basic safeguard.
Where can I buy it?
If you would like to try chlorella, the Genesis Vitamin online store sells Chlorella Caps. One point should be stated clearly: the online store’s shipping is $14.95 — it is not “free when you register”. Free shipping applies only when an order reaches the stated amount; for details, see the information on the store’s checkout page. Before buying, remember to check whether the product is “broken cell wall”, whether it has a Natural Product Number (NPN), and whether it has been third-party tested.
In closing
Chlorella’s real value is not in any magic effect. It is that chlorella is a concentrated green food: protein, chlorophyll, carotenoids and many micronutrients in one. Putting it back in that place — a supplement to everyday nutrition, not a medicine for treating disease — is the fairest introduction to this ancient algae.
This information is provided/written by David Chan, CNP, ROHP, and is educational only — it is not intended to replace the medical advice of your doctor. Please consult your doctor for advice about a specific medical condition. © Copyright Genesis Health Inc. All rights reserved.