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25 Health Benefits of Chlorella + Side Effects

Written by Biljana Novkovic, PhD | Last updated:
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology) | Written by Biljana Novkovic, PhD | Last updated:

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Chlorella and Barley

Chlorella is not a well-known alga in Western culture. However, its medicinal properties and assets are recently being considered for the treatment of diverse diseases, and as a source of several essential nutrients. Read on to learn about Chlorella, how it can help, and its potential side effects.

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].


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]:

  • Protein (Chlorella is 50% protein, and a great source of amino acids, including alanine, arginine, aspartic acid, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, and valine)
  • Vitamins (vitamin B1/thiamine, B2/riboflavin, B3/niacin, B5/pantothenic acid, B6/pyridoxine, B7/biotin, B9/folic acid, B12/cobalamin, and vitamin C)
  • Para-aminobenzoic acid
  • Β-carotene
  • Lutein
  • Minerals (including phosphorus, potassium, magnesium, calcium, iron, copper, zinc, manganese, and iodine)
  • Linoleic acid
  • Lycopene
  • Omega-3 fatty acids


Chlorella extract works by:

  • Decreasing inflammation: It decreases NFκB, TNF-alpha, nitric oxide, and inflammatory enzymes (COX, LOX, MPO); it also decreases the marker of chronic inflammation, hs-CRP [10, 11, 12, 13]
  • Improving immune function and resistance to infections [14]
  • Preventing allergies: It increases Th1 cytokines (IFN-gamma and IL-12) and decreases Th2 cytokines (IL-5) [15]
  • Preventing tumor growth: It decreases cell-survival factors Bcl-2, survivin, and XIAP, and increases cell-death-causing Bax [16, 17]
  • Boosting antioxidant levels: Chlorella contains various antioxidants and compounds that boost antioxidant enzyme levels [18]
  • Lowering the stress response (hypothalamic-pituitary-adrenal response) [19]
  • Improving detoxification of heavy metals and cancer-causing chemicals, and preventing radiation-induced damage [20, 21, 22, 23]
  • Increasing phase II detox enzymes and increasing the detox master-regulator Nrf2 [24]
  • Increasing GABA: Chlorella tablets are rich in GABA (y-aminobutyric acid), which widens blood vessels and thereby lowers blood pressure [25]

Chlorella’s chlorophyll and vitamin B12 can increase glutathione production, which improves the process of detoxification of toxins (such as heavy metals and insecticides) [26, 27].

Lutein, also present in Chlorella, is an inhibitor of an age-related vision loss condition (macular degeneration) and an anticataract agent [28].

Health Benefits of Chlorella

1) Boosts Immunity

In a trial of 51 healthy participants, Chlorella tablets enhanced immunity. They increased NK cell activity, IL-1beta, and the Th1 response (INF-gamma) in people who ingested these tablets for 8 weeks [29].

Intense exercise can weaken the immune system. In a placebo-controlled study performed in 10 female athletes, 5 weeks of Chlorella prevented the decrease in immune function (measured by salivary immunoglobulin A) during a training camp for a competitive sport [30].

IgA is an antibody that represents the first line of defense against respiratory tract infections in the body [30].

Another study of 15 men, revealed that salivary IgA was increased in participants when they ingested Chlorella tablets for 4 weeks [31].

Furthermore, a study performed in 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 [32].

Chlorella protects mice from E. coli and Listeria monocytogenes infection [33, 34].

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) [35].

Also in mice, C. vulgaris prevented the immunosuppressive effects caused by stress [36].

In mouse cells, C. vulgaris increased the production of IL-6 and IL-1a, which are stimulators of immune responses [36].

2) Increases 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 [18]:

  • Vitamin C
  • Vitamin E
  • Glutathione (GSH)
  • Superoxide dismutase activity (SOD)
  • Glutathione peroxidase activity (GPx)
  • Catalase activity (CAT)
  • Total antioxidant status

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 [37].

3) May Have Anti-Inflammatory Properties

Lycopene isolated from Chlorella marina lowered inflammatory enzymes (COX, LOX, and MPO), improved blood markers (including CRP, hemoglobin, and white and red blood cell counts), and markedly decreased swelling in the paw and joints of rats with arthritis. It had more potent activity than tomato lycopene [11].

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 [12].

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) [13].

4) May Prevent 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 [15].

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) [38].

Consequently, C. vulgaris may be helpful for the prevention of allergic diseases that prevalently induce humoral immunity (Th2 response) [38].

C. vulgaris also suppressed histamine release in mice mast cells by inducing Th1 IFN-gamma and IL-12 production [39].

Moreover, in human mast cells, C. vulgaris inhibited the production of IL-5 [15].

5) Helps Improve Cholesterol

Recently, a meta-analysis of 19 randomized control trials with 797 subjects revealed that Chlorella significantly decreased total and LDL cholesterol [40].

Although Chlorella (according to the meta-analysis) was beneficial for decreasing heart disease risk factors and fat cell size, there was no significant evidence that it could help with weight loss [40].

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 [41].

6) Helps Improve Blood Sugar

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 [42].

A meta-analysis of 19 randomized control trials with 797 subjects revealed that Chlorella significantly decreased fasting blood glucose [40].

In mice, C. pyrenoidosa enhanced the glucose-lowering effect of insulin (thereby increasing insulin sensitivity and decreasing insulin resistance) [43, 44].

According to results obtained from mice studies, Chlorella enhanced glucose uptake by liver and muscle cells, decreased non-esterified fatty acid levels and consequently, lowered blood glucose [43, 45].

7) Decreases 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 [25].

A meta-analysis of 19 randomized control trials with 797 subjects revealed that Chlorella significantly decreased systolic and diastolic blood pressure [40].

8) May Prevent Stroke

In stroke-prone rats with high blood pressure, the combined action of multiple ingredients of Chlorella powder (C. regularis), containing carotenoids and arginine, improved blood vessel function, decreased the incidence of stroke, and increased lifespan [46].

9) May Combat Diabetes

A placebo-controlled study with 57 borderline diabetic patients showed that genes were modified in individuals who consumed Chlorella tablets for 12 weeks in such a way that alleviated some features of type 2 diabetes [47]:

  • It decreased the production of resistin, which has been linked to insulin resistance.
  • It increased the adiponectin receptor (ADIPOR1), which is generally low in patients with insulin resistance. Adiponectin is a hormone that improves insulin resistance by promoting fatty acids and glucose breakdown.

Chlorella reduced cataract formation in diabetic rats by decreasing the oxidative stress in the lens [28].

10) May Help Fight Cancer

C. vulgaris extract increased the lifespan of mice with tumors by stimulating the production of white blood cells (granulocytes and macrophages) [48].

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) [16].

C. pyrenoidosa improved breast cancer in mice by decreasing tumor frequency. It significantly increased the production of cell death inducer caspase-7, while decreasing the production of a blood vessel growth factor receptor (VEGFR-2), which helps tumors grow by recruiting new blood vessels [49].

On the other hand, a study revealed how C. vulgaris promoted tumor growth in mice with breast cancer 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) [50].

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 [51].

Lycopene extracted from Chlorella (C. marina) suppressed the growth and induced the cell death of human prostate cancer cells [52].

11) May Have Anti-Aging Properties

A 2-month trial performed in 12 elderly subjects revealed that Chlorella decreased oxidative damage to red blood cells by reducing phospholipid hydroperoxide (PLOOH) concentrations, thus enhancing their ability to transport oxygen to the brain [53].

Hot water extract of C. vulgaris increased the lifespan of skin cells (fibroblasts) from both young and old individuals [54, 55].

C. vulgaris may have an anti-aging effect because it [54]:

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

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 [56, 57].

Although superoxide dismutase (SOD) is an antioxidant enzyme, it produces hydrogen peroxide that has to be removed by GPx and catalase. A study shows that as cells age, they have increased SOD activity, but reduced catalase and GPx, which causes the accumulation of hydrogen peroxide and cell aging. C. vulgaris reduced SOD levels in cells and thereby slowed cell aging [58].

12) May Be Beneficial for The Skin

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 [59].

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 [60].

Additionally, Chlorella decreased the production of an inflammatory mediator (TNF-a) and inhibited lipase, an enzyme produced by P. acnes that induces severe inflammation [60].

13) May Help Against Atopic Dermatitis

Chlorella improved atopic dermatitis symptoms in mice by [61]:

  • 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

14) May Improve Wound Healing

Chlorella extract improved skin reconstitution and accelerated wound healing when given to wounded mice at high doses (orally and topically) [62].

15) May Improve Brain Function

Chlorella (Parachlorella beijerinckii) prevented cognitive decline in a mouse model of dementia by reducing oxidative stress and decreasing the number of activated astrocytes (glial cells), which can cause brain inflammation and impairment [63].

In addition, Chlorella improved cognitive ability in mice; this could be due to its folic acid and antioxidant content [63].

Lipid extract of C. sorokiniana improved memory in rats by increasing noradrenaline and serotonin content in the hippocampus. Noradrenaline is a molecule (neurotransmitter) that regulates many brain functions: Attention, perception, arousal, sleep, learning, and memory, whereas serotonin regulates hippocampal electrical activity and cognitive performance [64].

16) May Help Against Parkinson’s

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 [65].

17) Helps Against Depression

A pilot 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 [66].

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 [66].

18) Combats Liver Diseases

Liver function improved in fatty liver disease (NAFLD) patients who consumed C. vulgaris tablets, in a trial performed in 60 individuals for 8 weeks [67].

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) [42],

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 [68].

In rats, Chlorella extracts protected against alcohol- and toxin-induced liver damage [24, 69].

19) May Improve Heavy Metal Detoxification

Parachlorella beijerinckii accelerated the excretion of methylmercury and consequently decreased tissue levels of mercury in mice [70].

Chlorella improved the elimination of radioactive strontium from mice through adsorption in the intestine. This means that Chlorella bound strontium after passing through the stomach, inhibiting absorption, and therefore enhancing its excretion from the body [71].

A study in pregnant mice revealed how C. pyrenoidosa suppressed methylmercury transfer to the fetus and reduced its accumulation in brains of the mothers [21].

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 [72].

C. vulgaris 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].

On the contrary, in one study, C. vulgaris was unable to increase cadmium excretion nor detoxification through urine in rats fed this heavy metal [73].

20) May Help Remove Toxins

A trial of 6 individuals revealed that Chlorella consumed for 2 weeks decreased urine levels of a cancer-causing heterocyclic amine [74].

In a study with 35 pregnant women, taking C. pyrenoidosa tablets for 6 months during pregnancy reduced the transfer of dioxins to children through breast milk [32].

Dioxins are highly toxic, cancer-causing chemicals.

In mice, C. pyrenoidosa accelerated the breakdown of dioxins, preventing their accumulation in the liver [75].

In rats, Chlorella promoted dioxins excretion into feces by inhibiting the absorption of dioxins from the digestive tract [76, 77].

Chlorella had a protective effect against carcinogenic heterocyclic amines in rat colon because it [20]:

  • Increased the excretion of these cancer-causing compounds through feces
  • Decreased DNA damage
  • Reduced the production of 2 important cancer-causing proteins (b-catenin and cyclin D1)
  • Reduced the cell death inducer caspase-8 in colon tissue

21) May Protect From Radiation

C. vulgaris had a protective effect in mice irradiated with gamma-rays by decreasing the damage to red blood cell precursors (a decrease of micronucleated polychromatic erythrocytes), and preventing the decrease of bone marrow cells [22, 23].

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 [78].

22) Increases Endurance and Stamina

A 14-day study performed in 10 individuals revealed that Chlorella increased aerobic endurance capacity by improving maximum oxygen uptake [79].

C. vulgaris improved physical stamina in mice [80].

In rats, Chlorella consumption, combined with high-intensity intermittent exercise, enhanced exercise performance and improved muscle metabolism by increasing the activity of the enzymes [81]:

  • Lactate dehydrogenase (LDH)
  • Phosphofructokinase (PFK)
  • Citrate synthase (CS)
  • Cytochrome-c oxidase (COX)

23) May Decrease Fatigue

A pilot trial performed in 18 fibromyalgia patients revealed that 2 months of ingesting Chlorella tablets decreased pain intensity [82].

A trial performed in 45 breast cancer patients showed that 50% of individuals who consumed Chlorella extract for 1 month had a better quality of life, were feeling less fatigue, and had better skin and hair quality, [83].

24) May Prevent 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 [84].

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) [84, 85].

25) May Combat Stress

C. vulgaris prevented psychological stress by suppressing the increase in serum corticosterone level (a mouse analog of cortisol) [86].

C. vulgaris reduced the effects of stress in mice by lowering the hypothalamic-pituitary-adrenal response. This means that Chlorella caused a decrease in [19]:

  • Adrenocorticotropic hormone response (ACTH)
  • Corticotropin-releasing factor expression (ACTH precursor)
  • Excess blood sugar (induced by stress)
  • C-fos expression (a stress response marker)

C. vulgaris decreased ulcer incidence in stressed rats and showed a protective effect against stress-induced ulcers [87].

Limitations and Caveats

Although many studies have shown that Chlorella may fight certain diseases, some of them were only evaluated in animals or cells. Further research in humans is needed to corroborate its efficacy.

Side Effects & Precautions

Minor side effects are relatively common and may occur in as many as 18% of consumers. Common side effects of Chlorella are [88, 5]:

  • Nausea and vomiting
  • Stomach cramps
  • Constipation
  • Diarrhea
  • Headaches
  • Dizziness
  • Fever
  • Weakness
  • Hearing problems
  • Vision problems
  • Insomnia
  • 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 [88].

Some people develop allergies to Chlorella or its components [89].

Chlorella can cause kidney injury in people who are allergic [90].

Drug Interactions

Chlorella interacts with warfarin, by decreasing its anticoagulant effect and increasing platelet aggregation [91, 92].

Some suggest that Chlorella may interfere with immunosuppressive drugs. However, there is no evidence to support this statement [88].

Chlorella vs. Spirulina

Diverse trials have exposed many of the health benefits of Chlorella and spirulina.

Chlorella increases insulin sensitivity, enhance immune system function, counteract the effects of free radicals, and decrease 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 [93].

Spirulina has a greater quantity of beta-carotene and protein content than Chlorella, whereas Chlorella has a better protein quality for human nutrition [93].

According to registered data obtained from microalgae consumers, spirulina has a higher rate of adverse events than Chlorella [88].



The recommended daily intake is below 10 g [88].

User Experiences

“I just started this a couple of weeks ago. Let me tell you, please start out very slow! My body is detoxing right now and I have been sick from the detox of Chlorella for about a week now. Stomach cramps, diarrhea, and nausea. I knew to expect these common side effects. I am here to clarify it is true! Start out very slowly with this and work yourself up in pills every day. Wow, it is scary to think how bad a person’s body is when the cleansing of Chlorella causes such discomfort. I have never felt so sick in my life. but it is well worth it. Would go through it all over again. Hope the worst is over.”

“When I take only 5 tablets per day, the detox effect is such that the white of my eyes looks bright and clear. I did not experience any kind of discomfort from taking this supplement, building up from 1 to 5 tablets per day.”

“I don’t normally write reviews, however as I developed severe nausea and vomiting from this product I decided to share this experience. For the first few weeks, I was tolerating it well. I was getting mild headaches and mild upset stomach. But I thought these were maybe detox symptoms. However, symptoms became worse, and so I stopped taking them. My symptoms went away after about 24 – 48 hours. Then I decided to try again, and immediately about 3 hours later woke up from sleep and had an extreme amount of nausea followed by 5 minutes of intense vomiting. I have not vomited in maybe 9 years before this. I have not had Chlorella before on an ongoing basis, but I have had spirulina for a long period with no issues.”

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About the Author

Biljana Novkovic

Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science & health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.

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