Chlorella: An Algae-Based Supplement Rich in Nutrients

Chlorella (Chlorella pyrenoidosa or Chlorella vulgaris) is a bright green algae dense in nutrients. It is considered a "superfood" because it contains protein, iron, dietary fiber, B vitamins, and complex carbohydrates.1

It's easy to grow, with uses that have been studied for treating high cholesterol, managing blood sugar, improving pregnancy-related anemia, and more. Additional research is needed, however, to confirm evidence of these and other health benefits.

What Is Chlorella?

Chlorella is a nutrient-dense, mainly freshwater algae. Scientists have discovered 20 chlorella species and over 100 strains.1 However, the two most commonly studied types of chlorella include Chlorella pyrenoidosa and Chlorella vulgaris.

Chlorella can be easily cultivated over large areas and has a high growth rate, making it both a sustainable ingredient and an efficient high-protein food substitute.2 Many countries produce chlorella, which can be found in foods like candies, gums, pasta, noodles, breakfast cereals, and beverages.

It is also available as a supplement in tablet, capsule, powder, and extract forms.

Chlorella has been studied for its potential to lower cholesterol levels and help reduce anemia risk during pregnancy, among other possible benefits.1 Some claim it can treat a range of health conditions. However, there is not enough evidence to support most of these claims.

Health Benefits of Chlorella

Below are a few possible health benefits of chlorella.

Nutrient-Dense

It’s called a "superfood" because it contains protein with vitamin D2 and all essential amino acids, iron, dietary fiber, B vitamins, complex carbohydrates, and more.1

In addition, chlorella contains antioxidant carotenoids like lutein, beta-carotene, and zeaxanthin. It also has high levels of other antioxidants like vitamin C and omega-3 fatty acids, which combat free radicals.1

A 2-teaspoon (5-gram) serving of chlorella contains the following:3

• Energy: 15 kcal
• Protein: 3 grams (g) 
• Carbohydrate: 2 g
• Calcium, Ca: 16.6 milligrams (mg)
• Iron, Fe: 12 mg, 70% of your RDA
• Vitamin C: 1 mg
• Vitamin B12: 15 micrograms (mcg), or 250% RDA
• Vitamin A: 2920 IU, or 60% RDA
  

Lowers High Cholesterol

High cholesterol is a risk factor for heart disease. Diet modifications are recommended for reducing cholesterol levels when they're high. Medications are also often prescribed to treat high cholesterol levels. However, there is much interest in alternative ways to reduce cholesterol. Chlorella has improved lipid levels in several studies. 

A 2014 study found that 416 mg of chlorella daily lowered total cholesterol, triglycerides, and LDL ("bad") cholesterol and increased HDL ("good") cholesterol.4 A 2022 meta-analysis noted similar benefits for reducing total and LDL cholesterol at 1,500 mg daily but not at higher doses.5

In 2018, a meta-analysis of randomized controlled trials found that 4 g of chlorella taken daily significantly reduced cholesterol, blood pressure, and blood sugar.6

It’s been suggested that the vitamin B12, niacin, and folate levels in chlorella may further bolster heart health.1

More research is needed before recommending chlorella for high cholesterol. Speak with your healthcare provider before starting any supplement.

Reduces Anemia Risk During Pregnancy

During pregnancy, iron requirements increase. Anemia can develop if an iron deficiency occurs. Chlorella happens to be a great source of iron.

In a 2010 study, Japanese researchers gave 70 pregnant women either 6 grams (6,000 milligrams) of chlorella or a placebo (no treatment) daily from 12 to 18 weeks of pregnancy until delivery. Those taking chlorella had higher hemoglobin levels in the second and third trimesters compared to the placebo group.7 

Chlorella also lowered rates of edema (tissue swelling), proteinuria (protein in urine), and gestational hypertension (high blood pressure during pregnancy).

While promising, further research is needed. It’s also advisable to avoid supplements during pregnancy unless you’ve cleared it with your healthcare provider. 

May Lower Blood Sugar

Chlorella has lowered blood sugar levels in several clinical trials. This may impact people with diabetes or those looking to moderate their glucose levels.

For example, a 2015 randomized trial concluded that chlorella supplementation may be useful in preventing or lessening the course of type 2 diabetes development in borderline diabetics.8

A 2021 study using 1,500mg of chlorella daily lowered blood sugar and cholesterol levels in people with diabetes.9

Further study is needed. Be mindful of using chlorella and blood-sugar-lowering medications together. 

May Reduce Blood Pressure

Chlorella has lowered blood pressure levels in clinical studies. This may benefit people with hypertension.

A systematic review published in 2018 suggested that four grams or higher daily of chlorella for eight weeks or more significantly reduced the participants' systolic and diastolic blood pressure.6

While promising, further research is warranted.

May Enhance Physical Exercise

Scientists have studied the impact of chlorella on physical exercise, specifically for performance and recovery.310

A 2023 review suggested chlorella improved the following:11

• Anaerobic and aerobic exercise performance
• Physical stamina
• Fatigue

The review concluded that these effects might be due, in part, to chlorella’s protein, fiber, fatty acid, and antioxidant content. 

More studies are needed to confirm these promising results.

May Bolster Eye Health

Chlorella contains noteworthy carotenoids to bolster your eye health. 

A single 6-gram dose of C. vulgaris in healthy males increased lutein, zeaxanthin, and beta-carotene levels in the body.12

If you have age-related macular degeneration (AMD) in one or both eyes, science suggests that special dietary supplements called AREDS 2 help slow vision loss.13

AREDS 2 typically contains the following nutrients: 

• Lutein
• Zeaxanthin
• Copper
• Zinc
• Vitamin C
• Vitamin E

Chlorella may be promising for supporting eye health, with a nutrient profile that includes carotenoids used in supplements engineered for eye health. However, further research is needed.

Benefits Liver Health

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly nonalcoholic fatty liver disease, is a condition that abnormally deposits fat in the liver. It affects an estimated 32% of the global adult population.14

A clinical trial of 70 people with MASLD used 1.2 g/day C. vulgaris or a placebo for eight weeks. The chlorella treatment lowered liver enzymes and increased serum insulin levels compared to the placebo group.15 

Chlorella supplementation may benefit blood sugar, inflammation, and liver function in people with MASLD.

May Help Symptoms of Fibromyalgia

Some preliminary (early) evidence indicates that chlorella supplementation can help to reduce pain symptoms associated with fibromyalgia.

In one study, a combination of chlorella tablets and liquid extract helped reduce pain symptoms compared to a placebo.16

More research would help determine the best form of supplement and appropriate doses. If you are considering using chlorella, be sure to talk with your healthcare provider.

Reduces Toxins

Researchers have investigated chlorella’s ability to decrease toxins in the body. In a preliminary animal study, chlorella supplementation increased the ability to eliminate dioxin, a potent carcinogen.17

In humans, chlorella supplementation (100 mg daily) for two weeks decreased the excretion of carcinogenic (cancer-causing) heterocyclic amines. This research suggests chlorella may help inactivate cancer-causing molecules.18

Methylmercury (MeHg) is a metal compound toxic to the brain, nervous system, and kidneys. Results of a 2018 clinical trial suggest that supplementation with chlorella for 3 months in healthy people might reduce their whole-body levels of MeHg.19

While these effects are promising, more research is needed. 

Has Antioxidant Effects

Chlorella is packed with antioxidant carotenoids like lutein, beta-carotene, and zeaxanthin.12 It contains high levels of other antioxidants like vitamin C and omega-3 fatty acids, which combat free radicals.1

Research centered on older adults using 8 g of chlorella daily for two months showed increases in carotenoid and antioxidant status. The treatment also lowered phospholipid hydroperoxide (PLOOH) concentrations, which build up abnormally in the red blood cells of people with dementia.20

It's plausible that chlorella has antioxidant effects.

Side Effects of Chlorella

Chlorella is generally considered safe and well tolerated. That said, chlorella can cause side effects, especially during the first few weeks of treatment. These include:21

• Stomach cramps
• Nausea
• Gas
• Diarrhea
• Green stool

Additionally, some have reported allergic reactions, including asthma and anaphylaxis.21

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

Should I Take Chlorella?

Chlorella may be safe for most people. However, here are a few things to consider before trying it:

• Allergy: If you’re allergic to chlorella, you may want to avoid using it. People allergic to mold may also be allergic to chlorella. To be safe, take a smaller "test" dose of chlorella and wait 24–48 hours to see if any allergy symptoms develop. The same concerns apply if you are intolerant to iodine because chlorella contains this trace mineral.22
• Breastfeeding: Chlorella can cause breast milk to turn green, which may be considered harmless. However, dietary supplements may contain ingredients not listed on the label or listed in incorrect amounts.21 It is best to consult a healthcare provider about chlorella use when breastfeeding or planning to breastfeed.
• Children: Chlorella's safety for children isn’t established yet.
• Thyroid conditions: Chlorella contains iodine. Iodine can cause reactions in people with thyroid disease. Excessive iodine can worsen hyperthyroid symptoms or cause an "iodine crash" in people with hypothyroidism.23

Interactions

Chlorella may interact with some medications, such as the following:

• Warfarin: Chlorella contains high amounts of vitamin K, promoting blood clotting and reducing the effectiveness of blood thinners like Jantoven (warfarin).24 Consult your healthcare provider before taking any supplements, including chlorella.
• Medications that increase sensitivity to sunlight: Chlorella may increase photosensitivity (sensitivity to sunlight) which can be a side effect of taking certain medications that put you at a greater risk of sunburn.21 Be sure to use sunscreen or stay out of the sun.
• Blood-sugar-lowering medications: Chlorella has been shown to lowered blood sugar levels in several studies.96 Be mindful of using chlorella and blood-sugar-lowering medications together, as chlorella may increase the effectiveness of your medication.

Reach out to your healthcare provider before adding chlorella to your diet.

How to Take Chlorella

There are no guidelines for the appropriate use or amounts of chlorella to take.

Common daily intake orally ranges from 3 g to 10 g.23

Never exceed the dose the manufacturer recommends. It's best to start with a small amount and increase the dose gradually. Doing so may help you avoid gastrointestinal and other side effects.

Tablets are the easiest form of chlorella to take because the dose remains controlled and consistent. If taking it as a powder or liquid, stick to the exact measurements recommended.

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

Similar Supplements

Spirulina and kelp are two other popular algae-based supplements.

Spirulina is a blue-green algae that contains nutrients, including fat-soluble vitamins, beta carotene, and minerals.

Kelp is a type of brown seaweed that typically grows in underwater forests. It provides nutrition for sea life but is also a food staple for humans. As a supplement, it often serves as a source of iodine.25

Summary

Chlorella is an algae-based supplement rich in vitamins, minerals, fiber, and antioxidants. It is frequently promoted as a good source of these nutrients for people who don't consume adequate fruits and vegetables in their diet. While some research has been promising, there is not enough evidence to support many of chlorella's purported health benefits.

Chlorella may interact with certain medications, and there are other precautions you should be aware of before using it. It's always best to speak with your healthcare provider before adding any supplement to your diet, particularly if you are taking any medication or have a chronic condition.