2–5 g/day.
Human evidence is very weak.
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Chlorella is a group of unicellular freshwater microalgae (the most commercialized species are Chlorella vulgaris and Chlorella pyrenoidosa) that have been cultivated industrially since the mid-20th century as a nutritional supplement, mainly in Japan, Taiwan, and China, where they are considerably popular as a general tonic and as an aid for "detoxification" of heavy metals and environmental pollutants; its nutritional profile is remarkably dense (complete protein at 60 percent of dry weight, chlorophyll, beta-carotene, vitamin B12 analogs, iron, calcium, nucleic acids, and fiber) and, together with spirulina, it is one of the most clinically studied microalgae.
Unlike spirulina (a cyanobacterium, not a true alga), chlorella has a rigid cellulosic cell wall that the human digestive system cannot break down, so it requires specific industrial processing (pressure disruption, ultrasound, or enzymatic treatment) to release the intracellular nutrients; commercial products usually specify "broken cell wall" as a marker of adequate processing, an important feature for the bioavailability of the intracellular components.
The most commercially promoted indication is the "detoxification" of heavy metals (mercury, lead, cadmium, arsenic): chlorella has a documented chemical affinity for some heavy metals through sulfide groups in its cell wall and proteins, but the clinical translation of this chemical capacity into actual removal of heavy metals accumulated in human tissues is very modest and far below that of specific pharmacological chelators (EDTA, DMSA, DMPS) when there is documented poisoning requiring treatment.
In contexts of mild chronic occupational exposure or population concern about environmental pollutants, chlorella has a reasonable nutritional profile, but the specific effects on the body burden of heavy metals are quantitatively small and predominantly speculative in people without significant toxic exposure; people with documented clinical poisoning should be evaluated and treated by specialists with specific pharmacological chelators, not with chlorella as a substitute.
As a nutritional source, chlorella is a dense source of nutrients that can contribute complete protein, iron, B vitamins (with the important caveat that the "vitamin B12" in chlorella is predominantly pseudovitamin B12, which is not biologically active for humans), antioxidants, and fiber; in people on strict vegetarian diets, chlorella can be a useful complement, although it does not replace specific vitamin B12 as cyanocobalamin or methylcobalamin.
In small studies, several trials have documented improvements in immune parameters (T lymphocytes, NK cells, serum immunoglobulins) and reductions in the frequency of seasonal respiratory infections with supplementation at 5-10 grams daily for 8-12 weeks, an indication consistent with the immunonutritional profile and with traditional Japanese use.
In mild hypertension, some studies have documented modest reductions in blood pressure; in dyslipidemia, the effects on lipid profile are inconsistent and small in magnitude; in pregnancy, several Japanese studies have documented improvements in parameters of gestational anemia and reductions in markers of dioxin toxicity with regular consumption, interesting data but predominantly local.
The doses studied range from 3 to 10 grams daily of powder or tablets, divided into several doses with meals; products with a "broken cell wall" or otherwise properly processed are significantly more bioavailable than unprocessed ones; chlorella has a characteristic intense taste (grassy with bitter and mineral notes) that many people find hard to accept; tablets are more palatable than powder for sustained use.
Generally well tolerated at moderate doses; the most frequent adverse effects are mild digestive discomfort at the start of treatment (gas, loose stools, occasionally diarrhea), which typically resolve within a few weeks with continued use; people with autoimmune diseases should be cautious because of theoretical immunostimulant activity; those taking warfarin-type anticoagulants should be cautious because the high vitamin K content can interfere with the INR; people with a mold allergy or environmental sensitivity may have cross-reactions; cheap products of uncertain origin may be contaminated with heavy metals or cyanotoxins, which paradoxically turns the "detox" supplement into a source of contamination, an important consideration when choosing products with specific purity certifications; in pregnancy and breastfeeding it has traditionally been used without problems, but it is advisable to choose certified products; people who expect significant heavy metal "detoxification" from chlorella are overestimating the real magnitude of the effect, which is modest and secondary to the general nutritional profile.
Information, not medical advice. Scientific evidence reflects the quality of the studies.