What are the side effects of chlorella on the liver?

November 28, 2025 •

4 min read

While typically considered safe for short-term use, some studies show chlorella supplementation is associated with mild side effects like digestive upset in the initial weeks of use. Before adding this green algae to your diet, it is important to understand what are the side effects of chlorella on the liver, as well as its potential benefits and risks.

Quick Summary

Chlorella is generally regarded as safe for short-term use and may even offer liver benefits, but risks exist from contaminated products that can lead to liver damage. Understanding potential gastrointestinal discomfort, allergic reactions, and drug interactions is also important.

Key Points

Positive Liver Effects: Rather than being harmful, chlorella has shown potential in studies for supporting liver health, particularly in cases of non-alcoholic fatty liver disease (NAFLD), by improving liver enzyme levels and metabolic function.
Contamination is a Concern: The most significant risk to the liver from chlorella is not the algae itself, but potential contamination with dangerous toxins like microcystins, which can cause liver damage.
Source Reputable Products: To avoid risks from contamination, it is crucial to purchase chlorella supplements from manufacturers that provide evidence of third-party testing for purity and toxins.
Mild Gastrointestinal Side Effects: Many people experience mild digestive issues, such as nausea, gas, and green stools, especially when first starting supplementation. These typically subside with continued use.
Drug and Condition Interactions: Chlorella can interact with certain medications, such as blood thinners and immunosuppressants, and may be unsuitable for individuals with autoimmune diseases or iodine sensitivity.
Detoxification Support: Chlorella's ability to bind to and remove heavy metals from the body is a well-regarded function that helps reduce the toxic load on the liver.

Chlorella: A Closer Look at Liver Health

Chlorella is a type of green freshwater algae that is widely marketed as a dietary supplement due to its rich nutritional profile, containing protein, vitamins, minerals, and antioxidants. Many users turn to chlorella for its purported detoxifying properties and overall health benefits, including liver support. While a growing body of research supports chlorella's potential advantages for liver health, it is crucial to examine the full picture, including potential risks and side effects, particularly regarding the liver.

How Chlorella Supports Liver Function

Rather than causing harm, studies have consistently shown that chlorella may actually support and protect the liver. Several mechanisms contribute to this effect:

Antioxidant Action: Chlorella is packed with antioxidants like chlorophyll, beta-carotene, and vitamin C, which help neutralize free radicals and reduce oxidative stress. This is vital for the liver, which is heavily involved in metabolic processes that can produce free radicals.
Detoxification Aid: A key function of chlorella is its ability to bind to heavy metals and other toxins, facilitating their removal from the body. This reduces the burden on the liver, allowing it to function more efficiently. Animal studies, for example, have shown that chlorella can help mitigate liver damage from heavy metal toxicity.
Improvement in Fatty Liver Disease: In human clinical trials, chlorella supplementation has been shown to improve markers of liver health in patients with non-alcoholic fatty liver disease (NAFLD). Participants experienced significant reductions in liver enzymes (like AST) and improvements in blood sugar and lipid profiles.
Reduction of Inflammation: Chlorella's anti-inflammatory properties can help reduce liver inflammation, which is a key factor in conditions like NAFLD.

Potential Risks and What to Watch For

While direct evidence of chlorella causing liver damage in a non-contaminated state is scarce, there are specific risks and side effects to be aware of. The most significant threat comes from contaminated products.

Potential Risks from Contaminated Chlorella

The primary concern regarding liver harm from chlorella is the risk of contamination with toxic substances.

Microcystins and Anatoxins: Certain types of blue-green algae can be contaminated with these highly toxic substances. The side effects of ingesting contaminated algae can be severe and include liver damage, stomach pain, nausea, vomiting, and in rare cases, death. It is essential to only purchase chlorella from reputable manufacturers that test their products for toxins and heavy metals.

Other Chlorella Side Effects Not Directly Liver-Related

For most people, side effects are mild and primarily gastrointestinal. They tend to occur during the first week of use as the body adjusts to the supplement. Common side effects include:

Nausea and stomach cramps
Diarrhea or green-colored stools
Bloating and gas
Increased skin sensitivity to the sun

Who Should Exercise Caution?

Certain individuals should be particularly careful when taking chlorella:

Individuals with Autoimmune Diseases: Chlorella may stimulate the immune system, which could potentially worsen the symptoms of autoimmune diseases such as multiple sclerosis, lupus, or rheumatoid arthritis.
Those on Immunosuppressive Medication: Because chlorella stimulates the immune system, it can interfere with immunosuppressive drugs.
People with Iodine Sensitivity or Thyroid Issues: Chlorella can contain iodine, which might cause an allergic reaction in sensitive individuals or affect those with hyperactive thyroidism.
Those on Blood-Thinning Medications: Chlorella contains vitamin K, which can interfere with the effectiveness of blood-thinning drugs like warfarin.
Pregnant or Breast-feeding Women: There is insufficient evidence to determine the safety of chlorella for these individuals.

Chlorella vs. Spirulina: A Comparative Look

Both chlorella and spirulina are popular microalgae supplements, but they have distinct differences in their nutritional profiles and potential effects. This table outlines some key comparisons, particularly regarding liver-related uses.


Feature	Chlorella	Spirulina
Cell Wall	Thick, tough cell wall that requires processing ('cracked' or 'broken cell wall') to make nutrients bioavailable and aid detoxification.	Easily digestible cell wall.
Detoxification	Strong heavy metal binding and detoxification properties. Often preferred for liver and body detoxification.	Less noted for heavy metal detoxification compared to chlorella.
Liver Support	Studies indicate potential benefits for fatty liver disease (NAFLD) by improving liver enzymes and metabolic markers.	Offers some antioxidant support for liver function.
Nutrient Density	Rich in chlorophyll, vitamin A, iron, magnesium, and zinc.	Higher in beta-carotene and phycocyanin.
Primary Use	Often sought for liver and heavy metal detoxification.	Often used for boosting energy and athletic performance.
Contamination Risk	Requires careful sourcing to avoid contamination with toxins.	Can also be contaminated with toxins if not sourced properly.

Conclusion: Making an Informed Decision

Based on current research, the notion that chlorella is harmful to the liver appears largely unfounded, and in fact, studies suggest it may offer significant protective benefits, especially for those with conditions like non-alcoholic fatty liver disease. The primary risk of liver damage is associated with consuming contaminated chlorella products, which can contain dangerous toxins like microcystins. To mitigate this, always source chlorella from reputable brands that provide third-party testing for purity. Common initial side effects are generally mild and resolve as the body adjusts, but individuals with pre-existing conditions, autoimmune disorders, or those on specific medications should consult a healthcare professional before use. Ultimately, when responsibly sourced, chlorella is a supplement with promising hepatoprotective qualities, not a liver threat. For further reading, an authoritative source on the clinical effects can be found here.

Frequently Asked Questions

There is no robust evidence that properly sourced and uncontaminated chlorella causes liver damage. The main risk to the liver comes from contaminated products that may contain toxins like microcystins.

Yes, some human and animal studies have indicated that chlorella can be beneficial for those with non-alcoholic fatty liver disease (NAFLD). It has been shown to help improve liver enzyme levels, blood sugar, and lipid profiles in some patients.

The most common side effects are digestive issues, including gas, bloating, nausea, and diarrhea. These are often mild and temporary, especially during the initial phase of taking the supplement.

Chlorella is believed to support the liver's natural detoxification processes. It contains chlorophyll and fiber that can bind to heavy metals and toxins, helping the body to eliminate them.

To ensure your supplement is safe, purchase from reputable brands that test their products for toxins and heavy metals. Look for third-party certifications on the product label.

Individuals with autoimmune diseases, those on blood thinners or immunosuppressants, and people with iodine sensitivity should consult a doctor before taking chlorella. Pregnant and breast-feeding women should also exercise caution.

Yes, chlorella can interfere with certain medications. For example, its vitamin K content can reduce the effectiveness of blood thinners like warfarin. Its immune-stimulating properties can also counteract immunosuppressant drugs.