What Is Chlorella?

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

Chlorella tablets, pellets, powder, and extract

 Verywell / Anastasia Tretiak

Chlorella is a bright green algae comprised of 50% protein. It is also rich in iron, fiber, B vitamins, complex carbohydrates, polyunsaturated fats, and antioxidants like lutein and vitamin C. It is purported to have a host of benefits, including in the treatment of high cholesterol, cancer, and hepatitis C. There are over 30 different types of chlorella, the most common of which are Chlorella vulgaris and Chlorella pyrenoidosa.

Chlorella has been explored as an alternative food source since the 1940s. 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.

So, while it is used as food in Japan, chlorella is taken as a dietary supplement in the United States. In recent years, chlorella has been marketed as a "superfood" and sold in tablet, extract, granule, and powder forms to treat a wide range of health conditions.

Also Known As

  • Bulgarian green algae
  • Chlorelle
  • Yaeyama chlorella

What Is Chlorella Used For?

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 potential benefits, including the prevention or treatment of:

Some of the health claims are better supported by research than others, though that is not to suggest that there haven't been promising findings.

Here is what some of the research says.

High Cholesterol

According to a 2014 study published in Nutrition Journal, 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 LDL ("bad") cholesterol, but there were also increases in HDL ("good") 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 chlorella's high amounts of carotenoid, an antioxidant that 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 levels of liver inflammation.

Eighteen 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 a day. 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 reduced the inflammatory symptoms of the liver disease but did nothing to treat the underlying infection.

Aside from the study being small, it should also be noted that there was no control group.

Pregnancy Complications

There is also evidence, albeit scant, that chlorella can 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 their second and third trimesters. 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 folate, vitamin B-12, and iron, all of which are particularly 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 liver cancer (hepatocellular carcinoma) were treated with different concentrations of a Chlorella vulgaris extract. Other rats were untreated and used as a control group.

After three months, the rats treated with chlorella had increased levels of caspase 8, a protein that promotes apoptosis (a normal process in which older cells die in order to be replaced by new healthy ones). With cancer, apoptosis is impaired, allowing cancer cells to develop and multiply out of control.

Compared to untreated rats, rats treated with the chlorella extract had significantly higher levels of caspase 8. Moreover, they increased in tandem with the dose of the chlorella extract.

When viewed under the microscope, liver tissues taken from the chlorella-treated rats demonstrated far slower tumor cell growth (proliferation) than untreated rats.

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 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, which 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.

 Verywell / Anastasia Tretiak

Dosage and Preparation

Chlorella products 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.

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

Tablets are the easiest form of chlorella to use as the dose is controlled and consistent.

If using a powder or liquid, use exact measurements to avoid underdosing or overdosing.

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 dressings, 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 they have 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, doing so requires 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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6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. 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

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