The Health Benefits of Chlorella

Nutritious algae may fight high cholesterol, hepatitis C, and cancer

Chlorella is a bright green algae used as a food supplement in Japan and taken as a dietary supplement in the West. Chlorella has been explored as an alternative food source since the 1940s when it was found that the algae, when dried, was comprised of 50% protein. Chlorella is also rich in iron, fiber, B vitamins, complex carbohydrates, polyunsaturated fats, and antioxidants like lutein and vitamin C.

Chlorella in powder and liquid form on a wooden table
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Despite efforts to harvest chlorella on a production level, the cost of doing so became exorbitant. Chlorella was also not considered to be palatable to most Western tastes.

In recent years, chlorella has been marketed as a "superfood" and sold in supplement form to treat a wide range of health conditions. In the United States, chlorella is commonly found in tablet, extract, granule, and powder forms.

There are over 30 different types of chlorella algae, of which Chlorella vulgaris and Chlorella pyrenoidosa are the most common.

Also Known As

  • Bulgarian green algae
  • Chlorelle
  • Yaeyama chlorella

Health Benefits

Proponents of alternative medicine claim that chlorella can help boost immunity and promote the detoxification of cells. These properties are believed to translate to a plethora of health benefits, including the prevention or treatment of:

Some of the health claims are better supported by research than others. That is not to suggest that there haven't been promising findings. Here are some of the current research says.

High Cholesterol

According to a 2014 study published in Nutrition Journal reported a daily 416-milligram (mg) dose of chlorella improved blood lipid levels in 62 adults with moderately elevated cholesterol. Not only were there significant reductions in total cholesterol, triglycerides, and "bad" LDL cholesterol, but there were also increases in "good" HDL cholesterol.

Compared to a matched set of adults given a placebo, participants who were given chlorella experienced anywhere from four- to 20-fold improvements in key lipid markers. The effect was attributed to the high carotenoid content in chlorella, the antioxidant of which can help lower the risk of heart disease.

Hepatitis C

A 2013 study in the World Journal of Gastroenterology suggests that chlorella may aid in the management of chronic hepatitis C infection by reducing the level of liver inflammation.

According to the research, 18 adults with chronic hepatitis C infection were given a 30-milliliter (mL) dose of a chlorella extract twice daily along with a 1,500-mg dose of chlorella tablets two to three times daily. After 12 weeks, the participants experienced a significant reduction in liver inflammation as measured by aspartate aminotransferase (AST) and alanine aminotransferase (ALT) tests.

What chlorella did not alter was the hepatitis C viral load, meaning that chlorella reduces the inflammatory symptoms of the liver disease but does nothing to treat the underlying infection.

Pregnancy Complications

There is also evidence, albeit scant, that chlorella can also reduce the risk of a potentially dangerous [pregnancy complication known as preeclampsia.

In a 2010 study in the journal Plant Food for Human Nutrition, researchers in Japan provided 70 pregnant women with either a daily 6-gram (6,000-mg) dose of a chlorella supplement or a placebo. Treatment started from 12 to 18 weeks of gestation and continued until the time of delivery.

When compared to the placebo group, the women provided chlorella had significantly higher hemoglobin levels during the second and third trimester. Moreover, they had a lower incidence of edema (tissue swelling), proteinuria (protein in urine), and gestational hypertension (high blood pressure), all of which suggest a reduced risk of preeclampsia.

Chlorella is also a safe natural source of the folate, vitamin B-12, and iron needed during pregnancy.


As far-fetched as it may seem, chlorella may exert anti-tumor properties that may one day lead to the development of novel anti-cancer drugs.

According to a 2009 study from Malaysia, rats with chemically-induced hepatocellular carcinoma (liver cancer) were treated with different concentration of a Chlorella vulgaris extract. After three months, the rats treated with chlorella had increased levels of B-cell lymphoma 2 (Bcl-2), a protein known to trigger apoptosis (programmed cell death) in cancer cells. Higher doses correlated to higher Bcl-1 concentrations.

Moreover, compared to untreated rats, those given chlorella has a significantly decreased proliferation of hepatocytes (liver cells). Decreases in hepatocyte proliferation are associated with slower tumor growth as well as the regeneration of healthy liver cells.

While this in no way suggests that chlorella can prevent or treat cancer, it does suggest it may have a protective effect worthy of further investigation.

Possible Side Effects

Chlorella is generally considered safe and well-tolerated. With that said, chlorella can cause side effects, especially during the first few weeks of treatment. These include:

  • Flatulence
  • Green discoloration of stools
  • Nausea
  • Stomach cramps
  • Diarrhea

Most of these side effects tend to resolve as your body adapts to treatment.

Chlorella may also cause photosensitivity, increasing the risk of sun rash and sunburn. To help mitigate this effect, wear plenty of sunscreen and avoid excessive sun exposure.

People allergic to mold may also be allergic to chlorella. To be safe, take a smaller "test" dose of chlorella and wait 24 to 48 hours to see if any allergy symptoms develop. The same concerns apply if you have an iodine allergy since chlorella is especially high in iodine.

The high iodine content also poses a risk to people with thyroid disease, given that the excess intake of iodine can cause a worsening of hyperthyroid symptoms or an "iodine crash" in people with hypothyroidism.

Chlorella's safety in children has not been established.


Chlorella contains high amounts of vitamin K. Vitamin K can promote blood clotting and reduce the efficacy of blood thinners like Coumadin (warfarin) and Plavix (clopidogrel).

Chlorella also has a stimulatory effect on the immune system and can theoretically undermine the effectiveness of immunosuppressant drugs used to treat cancer and autoimmune diseases. These include drugs such as cyclosporine, prednisone, and TNF inhibitors.

To be safe, avoid chlorella if you are using any immunosuppressant drug.

Dosage and Preparation

Chlorella tablets, pellets, extracts, and powders can readily be sourced online as well as in many natural food stores and shops specializing in dietary supplements.

There are no guidelines for the appropriate use of chlorella. Most supplemental tablets are offered in 500-mg to 1,000-mg formulations. Doses of up to 6,000 mg daily have been used safely for up to 24 weeks, even in pregnancy.

Tablets are the easiest supplement to use as the dose is controlled and consistent. If using powders or liquids, use exact measurements to avoid underdosing or overdosing.

Never exceed the dose recommended by the manufacturer. If anything, start with the smallest possible dose and increase gradually. Doing so may help you avoid gastrointestinal side effects.

Chlorella powder can be mixed with water, juice, yogurt, and smoothies, but be aware that it has a slightly seaweedy smell and flavor. Some people find that adding it to vinaigrette dressing, miso soups, stir-fries, or wheatgrass can conceal the smell and taste. Cooking chlorella does not diminish its nutritional value.

What to Look For

Dietary supplements are not strictly regulated in the United States. To ensure quality and safety, opt for brands that have been tested and certified by an independent body like the U.S. Pharmacopeia (USP), ConsumerLab, or NSF International.

To avoid unwanted chemicals or preservatives, buy products labeled "pure" (meaning no added ingredients) that have been certified organic by the U.S. Department of Agriculture (USDA).

Though you may be tempted to buy the "real" chlorella from Asia, you need to do so with caution. If you cannot read the language on the product label, you can never know for sure what other ingredients may be in the supplement (or what ingredients may be missing).

According to the National Center for Complementary and Integrative Health, Chinese herbal remedies have been found to be contaminated with pesticides, heavy metals, drugs, and undeclared animal and plant products.

Finally, don't be swayed by health claims that may or may not be true. Just because a product is "natural" doesn't mean that it is safe. Use your best judgment, and avoid any product that claims to treat multiple unrelated disorders.

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  1. Kwak JH, Baek SH, Woo Y, et al. Beneficial immunostimulatory effect of short-term Chlorellasupplementation: enhancement of Natural Killer cell activity and early inflammatory response (Randomized, double-blinded, placebo-controlled trial). Nutr J. 2012;11:53. doi:10.1186/1475-2891-11-53.

Additional Reading
  • Azamai ESM, Sulaiman S, Habib SHM, et al. Chlorella vulgaris triggers apoptosis in hepatocarcinogenesis-induced rats. J Zhejiang Univ Sci B. 2009 Jan;10(1):14-21. doi:10.1631/jzus.B0820168.

  • Azocar J, Diaz A. Efficacy and safety of Chlorella supplementation in adults with chronic hepatitis C virus infection. World J Gastroenterol. 2013 Feb 21;19(7):1085-90. doi:10.3748/wjg.v19.i7.1085.

  • Nakano S, Takekoshi H, Nakano M. Chlorella pyrenoidosa supplementation reduces the risk of anemia, proteinuria and edema in pregnant women. Plant Foods Hum Nutr. 2010 Mar;65(1):25-30. doi:10.1007/s11130-009-0145-9.

  • National Center for Complementary and Integrative Health. Traditional Chinese Medicine: What You Need To Know. Bethesda, Maryland; updated April 29, 2019.

  • Ryu NH, Lim Y, Park JE, et al. Impact of daily Chlorella consumption on serum lipid and carotenoid profiles in mildly hypercholesterolemic adults: a double-blinded, randomized, placebo-controlled study. Nutr J. 2014 Jun 11;13:57. doi:10.1186/1475-2891-13-57.