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10 Chlorella Health Benefits + Side Effects & Reviews

Written by Aleksa Ristic, MS (Pharmacy) | Reviewed by Biljana Novkovic, PhD | Last updated:
Jonathan Ritter
Puya Yazdi
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology), Puya Yazdi, MD | Written by Aleksa Ristic, MS (Pharmacy) | Reviewed by Biljana Novkovic, PhD | Last updated:

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Chlorella and Barley

The medicinal properties and nutritional value of Chlorella can help shield the heart, brain, liver, and more. Asian traditions have used this microalga for centuries, and modern science now brings it to the west. Read on to learn about Chlorella health benefits, potential side effects, and user reviews.

What is Chlorella?

Chlorella is a type of single-celled green alga (microalga) that is usually found in freshwater environments. Some species of this microalga have myriad health benefits while being packed with essential nutrients [1, 2].

The interest in Chlorella production began in the 1960s when a Japanese company started to culture it on a massive scale, and by 1980 the production spread in Asia, reaching more than 1,000 kg of produced microalga (mainly Chlorella) per month [3].

Today, Chlorella is being used in Japan, the USA, Europe, and other countries. In East Asia, it is ingested with rice, tea, and pancakes. Furthermore, Chlorella is sold extensively as a supplement or nutraceutical product [4, 5].

Due to its high concentration of protein (50%), Chlorella is a good source of the essential amino acids required for our nutrition [6].

Snapshot

Proponents:

  • Reduced blood sugar and cholesterol
  • Protects the heart and liver
  • Prevents anemia
  • Supports detox
  • Combats oxidative stress
  • May improve mental health
  • May enhance physical performance

Skeptics:

  • Many benefits lack clinical evidence
  • May cause digestive upset and dizziness
  • Interacts with blood thinners

Components

Although the most frequently studied types of Chlorella are quite similar (Chlorella vulgaris and Chlorella pyrenoidosa), the composition may vary among different species [7, 6].

Chlorella’s main constituent is the Chlorella Growth Factor (CGF), an extract composed of diverse substances including essential amino acids, peptides, proteins, vitamins, sugars, and nucleic acids [2].

Chlorella’s principal components are [8, 5, 9]:

Anti-Inflammatory Properties

Lycopene isolated from Chlorella marina lowered inflammatory enzymes (COX, LOX, and MPO), improved inflammatory blood markers (CRP), and markedly decreased swelling in the paw and joints of rats with arthritis. It had a more potent activity than tomato lycopene [10].

Chlorella ellipsoidea reduced the activation of nuclear factor kappa B (NFκB), thus lowering inflammation in a type of white blood cell (macrophage) of mice fed with a high-fat and high-cholesterol diet [11].

A Chlorella component (Chlorella 11-peptide) suppressed the inflammatory cytokine TNF-alpha and an inflammatory mediator (nitric oxide) in both injured rats and white blood cell cultures (macrophages) [12].

Health Benefits of Chlorella

Possibly Effective:

1) Diabetes

A meta-analysis of 19 randomized control trials with 797 subjects revealed that Chlorella significantly decreases fasting blood glucose [13].

A study performed in 70 non-alcoholic fatty liver disease (NAFLD) patients revealed that those who ingested C. vulgaris for 8 weeks had reduced blood glucose levels [14].

In a placebo-controlled study with 57 borderline diabetic patients, Chlorella tablets for 12 weeks alleviated some features of type 2 diabetes by decreasing resistin production and increasing adiponectin receptor (ADIPOR1) [15].

In mice, C. pyrenoidosa enhanced the glucose-lowering effect of insulin (thereby increasing insulin sensitivity and decreasing insulin resistance) [16, 17].

According to the results obtained from mice studies, Chlorella enhanced glucose uptake by liver and muscle cells and, consequently, lowered blood glucose [16, 18].

It reduced cataract formation in diabetic rats by decreasing oxidative stress in the lens [19].

2) Cholesterol Levels

Recently, a meta-analysis of 19 randomized control trials with 797 subjects revealed that Chlorella significantly decreases total and LDL cholesterol [13].

Although it was beneficial for decreasing heart disease risk factors and fat cell size, there was no significant evidence that it could help with weight loss [13].

Chlorella (C. pyrenoidosa) dried powder decreased the levels of cholesterol (LDL and total cholesterol) and triglycerides (TG) and raised levels of good cholesterol (HDL) in animals (rats and hamsters) on a high-fat diet [20].

3) High Blood Pressure

A study performed in 80 individuals (with normal-high levels of blood pressure and borderline hypertension), showed that those who consumed GABA-rich Chlorella tablets for 12 weeks reduced their blood pressure significantly [21].

A meta-analysis of 19 randomized control trials with 797 subjects revealed that Chlorella significantly decreased systolic and diastolic blood pressure [13].

Taken together, the effects of Chlorella on blood sugar, cholesterol, and blood pressure indicate its potential to prevent heart disease, but clinical trials should investigate this further.

4) Immune Response

In a trial of 51 healthy participants, Chlorella tablets enhanced immunity. They increased NK cell activity, IL-1beta, and the Th1 response in people who ingested these tablets for 8 weeks [22].

Intense exercise can weaken the immune system. In a placebo-controlled study performed in 10 female athletes, 5 weeks of Chlorella supplementation prevented the decrease in immune function (measured by salivary immunoglobulin A) during a training camp [23].

Another study of 15 men, revealed that salivary IgA was increased in participants when they ingested Chlorella tablets for 4 weeks [24].

A study of 35 pregnant women showed increased IgA levels in the breast milk of women that consumed Chlorella for 6 months before giving birth. Higher levels of IgA in breast milk helps reduce the risk of infection in nursing infants [25].

It protected mice from E. coli and Listeria monocytogenes infection in two animal trials [26, 27].

In mice, Chlorella counteracted the effect of a chemotherapeutic drug (Cyclophosphamide) that suppresses the immune system by recovering NK cell function and increasing Th1 cytokines (IL-2, IL-12, TNF-a, IFN-y) [28].

Also in mice, C. vulgaris prevented the immunosuppressive effects caused by stress [29].

5) Antioxidant Activity

In a study performed in 38 smokers for 6 weeks, Chlorella reduced the levels of malondialdehyde in the blood, a marker of oxidative stress, and increased blood levels of 7 different antioxidant measures [30]:

Furthermore, another 6-week study with 52 smokers revealed that Chlorella powder increased blood levels of vitamin E (alpha-tocopherol) and vitamin C. It also raised the activity of superoxide dismutase and erythrocyte catalase [31].

In a 2-month trial performed in 12 elderly subjects, it decreased oxidative damage to red blood cells by reducing phospholipid hydroperoxide (PLOOH) concentrations, thus enhancing their ability to transport oxygen to the brain [32].

6) Liver Disease

Liver function improved in 60 fatty liver disease (NAFLD) patients who consumed C. vulgaris tablets for 8 weeks [33].

Another study of 70 fatty liver disease patients showed that Chlorella enhanced patients’ condition by reducing weight and blood glucose levels and decreasing inflammatory indicators (TNF-a and high-sensitivity C-reactive protein) [14],

Levels of alanine transaminase (ALT), a marker of liver inflammation, were significantly reduced in 85% of 18 hepatitis C patients treated with C. pyrenoidosa extract for 12 weeks [34].

In rats, Chlorella extracts protected against alcohol- and toxin-induced liver damage [35, 36].

7) Toxin Removal

A trial of 6 individuals revealed that Chlorella consumed for 2 weeks decreased urine levels of a cancer-causing heterocyclic amine [37].

In a study of 35 pregnant women, taking C. pyrenoidosa tablets for 6 months during pregnancy reduced the transfer of dioxins to children through breast milk [25].

Dioxins are highly toxic, cancer-causing chemicals.

In mice, C. pyrenoidosa accelerated the breakdown of dioxins, preventing their accumulation in the liver [38].

In rats, Chlorella promoted dioxins excretion into feces by inhibiting the absorption of dioxins from the digestive tract [39, 40].

It had a protective effect against carcinogenic heterocyclic amines in rat colon [41].

Heavy Metals

Parachlorella beijerinckii accelerated the excretion of methylmercury and consequently decreased tissue levels of mercury in mice [42].

Chlorella improved the elimination of radioactive strontium from mice through adsorption in the intestines [43].

A study in pregnant mice revealed how C. pyrenoidosa suppressed methylmercury transfer to the fetus and reduced its accumulation in the mothers’ brains [44].

C. vulgaris improved the condition of lead-exposed mice by increasing their levels of white blood cells (NK cells), IFNy, IL-1a, and TNF-a, and preventing a decrease in zinc bone concentrations [45].

It protected rats against cadmium liver toxicity by decreasing cadmium accumulation and stimulating the expression of metallothioneins in the liver. Metallothioneins are heavy metal-binding proteins found in the circulation and produced by several tissues in the body [6].

However, in one study, C. vulgaris was unable to increase cadmium excretion in rats fed this heavy metal [46].

8) Anemia in Pregnancy

In a study of 70 pregnant women, Chlorella supplementation (6 g daily, from the 12th-18th week of pregnancy) reduced the risk of anemia by 48%, compared to control [47].

This regiment also reduced leg swelling and urine protein loss but didn’t reduce the risk of gestational hypertension (high blood pressure during pregnancy) [47].

Insufficient Evidence:

No valid clinical evidence supports the use of Chlorella for any of the conditions in this section. Below is a summary of up-to-date animal studies, cell-based research, or low-quality clinical trials which should spark further investigation. However, you shouldn’t interpret them as supportive of any health benefit.

9) Physical Performance

A 14-day study performed in 10 individuals revealed that Chlorella increased aerobic endurance capacity by improving maximum oxygen uptake [48].

C. vulgaris improved physical stamina in mice [49].

In rats, Chlorella consumption, combined with high-intensity intermittent exercise, enhanced exercise performance and improved muscle metabolism by increasing the activity of crucial enzymes such as lactate dehydrogenase (LDH) [50].

10) Depression

A study performed in 125 patients with major depressive disorder showed improvement in depression and anxiety in patients who consumed C. vulgaris tablets in addition to their standard antidepressant medications for 6 weeks. That said, all improvements were subjective [51].

This result could be explained by the neuroprotective components contained in C. vulgaris (linoleic acid and vitamin B12/methylcobalamin), which have been reported to improve depressive symptoms [51].

Further research is needed to investigate the potential antidepressant effects of Chlorella.

Animal and Cellular Research (Lacking Evidence):

No clinical evidence supports the use of Chlorella for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based studies; they should guide further investigational efforts but should not be interpreted as supportive of any health benefit.

Allergies

C. vulgaris extract improved allergic inflammation in mice by inhibiting IL-5 production (IgE-dependent) and reducing the recruitment of major inflammatory cells to the allergic airways (eosinophils and neutrophils). IL-5 is an important cytokine involved in the development of allergic inflammation [52].

C. vulgaris enhanced cell-mediated immunity (Th1 response) in mice allergic to casein. It decreased IgE levels in the blood and increased cytokines that mitigate allergies (IL-12 and IFN-gamma) [53].

Consequently, it may be helpful for the prevention of allergic diseases that prevalently induce humoral immunity (Th2 response) [53].

C. vulgaris also suppressed histamine release in mice mast cells by inducing Th1 IFN-gamma and IL-12 production [54].

Anticancer Effects

The findings discussed below stem from animal and cell-based studies only. They should guide further investigation but shouldn’t be interpreted as supportive of the anticancer effects until more research is done. Chlorella supplements aren’t approved for cancer prevention or treatment

C. vulgaris extract increased the lifespan of mice with tumors by stimulating the production of white blood cells (granulocytes and macrophages) [55].

Another species of Chlorella (C. sorokiniana), killed human lung cancer cells and reduced tumor growth in mice (by decreasing cell-survival factors Bcl-2, survivin, and XIAP, and increasing cell death causing Bax) [56].

C. pyrenoidosa improved breast cancer in mice by suppressing its growth [57].

Hot water extract of C. vulgaris triggered the death of human liver cancer cells by increasing p53, Bax, and caspase-3. these proteins induce cell death [58].

Lycopene extracted from Chlorella (C. marina) suppressed the growth and induced the cell death of human prostate cancer cells [59].

On the other hand, a study revealed how C. vulgaris promoted breast cancer growth in mice when given in high doses (200 mg/kg). This may be a consequence of the expression of diverse cytokines that promote tumor growth (IFNy and IL-4 were decreased, while TGFβ1, IL-10, and IL-1b were increased) [60].

Clinical trials are needed to investigate the potential anticancer effects of Chlorella. At this point, it can’t be recommended for cancer treatment or prevention.

Anti-Aging Properties

Hot water extract of C. vulgaris increased the lifespan of skin cells (fibroblasts) from both young and old individuals [61, 62].

C. vulgaris may have an anti-aging effect because it [61]:

  • removes free radicals (due to its high levels of antioxidants)
  • inhibits telomere shortening (oxidative-stress-induced DNA damage)

Cells age when the telomeres (ends of chromosomes) are shortened. This happens every time your cells divide, with each round of replication (DNA synthesis). Therefore, increased telomerase activity boosts telomere production and increases the lifespan of cells [63, 64].

Although superoxide dismutase (SOD) is an antioxidant enzyme, it produces hydrogen peroxide that has to be removed by GPx and catalase. C. vulgaris reduced SOD levels in cells and thereby slowed cell aging [65].

That said, the anti-aging properties of chlorella haven’t yet been tested in clinical trials.

Cognitive Function

Chlorella (Parachlorella beijerinckii) prevented cognitive decline in mouse models of dementia by reducing oxidative stress and inflammation [66].

Lipid extract of C. sorokiniana improved memory in rats by increasing noradrenaline and serotonin content in the hippocampus [67].

Radioprotection

C. vulgaris had a protective effect in mice irradiated with gamma-rays by decreasing the damage to red blood cell precursors and preventing the decrease of bone marrow cells [68, 69].

Moreover, the water extract of Chlorella boosted the production of stem cells in the bone marrow and spleen, which increased the survival of mice after being irradiated with gamma rays [70].

Muscle Wasting

Chlorella improved the condition of mice with muscle atrophy by reducing oxidative stress and decreasing creatine phosphatase levels (a muscle impairment marker); it also helped to maintain the activity of the mitochondrial cytochrome c oxidase [71].

The loss of cytochrome c oxidase activity in mitochondria is a characteristic feature of an age-related condition in which the skeletal muscle loses its mass and strength (sarcopenia) [71, 72].

Stress

In mice, C. vulgaris prevented psychological stress by suppressing the increase in serum corticosterone levels (a mouse analog of cortisol) [73].

C. vulgaris reduced the effects of stress in mice by lowering the hypothalamic-pituitary-adrenal response (adrenocorticotropic hormone or ACTH response) [74].

In another animal trial, it decreased ulcer incidence in stressed rats [75].

Skin Benefits

Chlorella minutissima extract increased antioxidant enzymes (GST) while it decreased the activity of enzymes involved in skin disorders (tyrosinase and elastase). This extract could be potentially used in cosmetic products for irritated, reactive, and aging skin [76].

Another study suggested that some Chlorella extracts have an inhibitory effect on Propionibacterium acnes, a bacterium that has been described as one of the major causes of acne [77].

Atopic Dermatitis

Chlorella improved atopic dermatitis symptoms in mice by [78]:

  • Reducing white blood cells infiltration into the skin (eosinophils and mast cells)
  • Decreasing pro-inflammatory mediators (thymus- and activation-regulated chemokine and macrophage derived-chemokine)
  • Decreasing the levels of IL-4 and IFN-y cytokines

Wound Healing

Chlorella extract improved skin reconstitution and accelerated wound healing when given to wounded mice at high doses (orally and topically) [79].

Parkinson’s Disease

In a mouse model of Parkinson’s, polysaccharides from C. pyrenoidosa prevented the loss of dopamine and neuron death, inhibited inflammation, improved symptoms, and delayed disease progression [80].

Stroke Prevention

In stroke-prone rats with high blood pressure, Chlorella powder (C. regularis), containing carotenoids and arginine, improved blood vessel function, decreased the incidence of stroke, and increased lifespan [81].

Chlorella Side Effects & Precautions

This list does not cover all possible side effects. Contact your doctor or pharmacist if you notice any other side effects. In the US, you may report side effects to the FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada, you may report side effects to Health Canada at 1-866-234-2345.

Chlorella is likely safe for a general population. However, minor side effects are relatively common and may occur in as many as 18% of consumers. They include [82, 5]:

  • Digestive upset
  • Constipation
  • Headaches
  • Dizziness
  • Fever
  • Weakness
  • Itching and rash
  • Muscle pain

Pre-existing medical conditions, such as renal failure and hypothyroidism, but not Hashimoto’s thyroiditis, increase the risk of side effects [82].

Some people develop allergies to Chlorella or its components. It can cause kidney injury in people who are allergic [83, 84].

Chlorella is possibly safe during pregnancy, but pregnant women should use it only if prescribed by their doctor [47].

Drug Interactions

Supplement-drug interactions can be dangerous and, in rare cases, even life-threatening. Always consult your doctor before supplementing and let them know about all drugs and supplements you are using or considering.

Chlorella interacts with warfarin, by decreasing its anticoagulant effect and increasing platelet aggregation [85, 86].

Some suggest that Chlorella may interfere with immunosuppressive drugs. However, there is no evidence to support this statement [82].

Chlorella vs. Spirulina

According to preliminary research, Chlorella increases insulin sensitivity, enhances immune system function, counteracts the effects of free radicals, and decreases blood pressure [5].

On the other hand, spirulina improves hemoglobin, protein, and vitamin levels in malnourished children, increases immune function, has a great antioxidant capacity, and is a good source of beta-carotene [87].

Spirulina has a greater quantity of beta-carotene and protein content than Chlorella, whereas Chlorella has a better protein quality for human nutrition [87].

According to registered data obtained from microalgae consumers, spirulina has a higher rate of adverse events than Chlorella [82].

Dosage: The recommended daily intake of Chlorella is up to 10 g [82].

User Experiences

The opinions expressed in this section are solely from the users who may or may not have a medical background. SelfDecode does not endorse any specific product, service, or treatment. Do not consider user experiences as medical advice. Never delay or disregard seeking professional medical advice because of something you have read on SelfDecode.

One user experienced severe digestive discomfort which they think was caused by too strong detox process. They suggest going slow with Chlorella and gradually working up to higher doses, due to its potent detox properties.

Another user was building up from 1 to 5 tablets per day and reported good detox results with no side effects.

However, one person also experienced severe nausea and vomiting after a few weeks of Chlorella supplementation. The adverse effects disappeared upon the supplement cessation. The same person previously practiced long-term spirulina supplementation with no side effects.

About the Author

Aleksa Ristic

Aleksa Ristic

MS (Pharmacy)
Aleksa received his MS in Pharmacy from the University of Belgrade, his master thesis focusing on protein sources in plant-based diets. 
Aleksa is passionate about herbal pharmacy, nutrition, and functional medicine. He found a way to merge his two biggest passions—writing and health—and use them for noble purposes. His mission is to bridge the gap between science and everyday life, helping readers improve their health and feel better.

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