Is Chlorella Safe During Pregnancy?

Written by: Pard Bharaj



Time to read 8 min

Image of Pard, the Author

Author: Pard Bharaj

I am a dedicated researcher with nearly a decade of experience in investigating health best practices. 

Disclaimer: The information provided in this article is for educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition or before making any changes to your diet or lifestyle.


Chlorella, a type of green algae, has been part of the human food supply for centuries and is recognised for its high nutrient content. Specifically, Chlorella vulgaris and Chlorella pyrenoidosa are considered not novel in the EU under Regulation (EC) No 258/97, and Chlorella protothecoides has been recognised as Generally Regarded as Safe (GRAS) by the FDA in the United States. Despite its historical use and regulatory approvals, the available scientific research on the safety of consuming chlorella during pregnancy is limited. Some studies suggest that chlorella may be generally safe for pregnant women.

The American Pregnancy Association states that chlorella is generally safe in small to moderate amounts, but it is always best to consult with a healthcare provider before adding any supplements to your pregnancy diet. This ensures that any potential risks can be assessed based on individual medical histories and existing health conditions. 

Additionally, if you are interested in taking chlorella supplements, it is best to purchase an organic product from a trusted manufacturer and consult with a healthcare specialist first. Pregnant women should start with a small dosage of chlorella, monitoring their body’s response before gradually increasing the intake. It is also important to note that chlorella should not replace a healthy, balanced diet during pregnancy.

In this article, we will look at how chlorella could be beneficial, as well as the potential side effects for pregnant women. Summaries of relevant scientific studies are provided at the end of the article in "References and Further Reading".

How Chlorella Can Help During Pregnancy:

1. Nutritional Support:

  • Folate: Chlorella is a good source of folate, which is essential for foetal development and the prevention of neural tube defects. Adequate folate intake is crucial during pregnancy to support the healthy development of the baby‚Äôs brain and spine.

  • Iron: Rich in iron, chlorella can help prevent pregnancy-associated anaemia. Iron is vital for producing haemoglobin, which carries oxygen in the blood, ensuring both the mother and baby receive adequate oxygen.

  • Vitamins: Chlorella provides essential vitamins such as Vitamin B-12 and beta-carotene (a precursor of Vitamin A). Vitamin B-12 supports nerve function and the production of red blood cells, while beta-carotene is important for immune function and vision. However, it is important to monitor intake as excessive Vitamin A can be harmful during pregnancy.

2. Can Mitigate Pregnancy Issues: 

  • Anaemia:¬†Studies have shown that chlorella supplementation can reduce the risk of anaemia during pregnancy. Preventing anaemia is crucial for maintaining energy levels and overall health in pregnant women. Anaemia during pregnancy can lead to fatigue, weakness, and complications during childbirth. Chlorella‚Äôs high iron content, along with its ability to improve haemoglobin levels, makes it beneficial for preventing and managing anaemia.¬†
  • Pregnancy-Induced Hypertension (PIH):¬†Chlorella has been associated with lower incidences of proteinuria and edema, which are signs of PIH. By reducing these symptoms, chlorella may help in managing blood pressure and reducing the risk of complications associated with hypertension during pregnancy. The antioxidants and nutrients in chlorella may support vascular health and reduce inflammation, thereby helping to manage blood pressure and mitigate the symptoms of PIH.

3. Enhancing Immune Function: 

  • Immune Boosting Compounds: Chlorella contains bioactive compounds such as chlorophyll, beta-glucans, and vitamins C and E, which may enhance the immune system, potentially protecting against infections during pregnancy. Chlorophyll is known for its detoxifying properties and ability to strengthen the immune response.
  • Cell Activation: Beta-glucans, a type of polysaccharide, can boost the activity of macrophages, natural killer cells, and neutrophils, which are crucial for fighting off infections. Additionally, vitamins C and E act as antioxidants, protecting cells from damage and supporting overall immune function. Regular consumption of chlorella could therefore support the body's natural defenses, helping to reduce the likelihood of common infections and promote a healthier pregnancy. However, it is essential to consult with a healthcare provider before starting any supplementation to ensure it is appropriate for your specific health needs.

Chlorella Nutritional Table:

Is Chlorella Safe During Pregnancy? - Chlorella Nutritional Table:

Precautions, Side Effects and Concerns:


  • Consultation with Healthcare Provider: Always consult with a healthcare provider before taking chlorella supplements during pregnancy to ensure it is safe based on your individual health conditions.

  • Start with Small Dosage: Begin with a small dosage of chlorella and gradually increase it, while closely monitoring your body's response.

  • Potential Digestive Issues: Some pregnant women may experience digestive issues such as diarrhoea, bloating, or gas when taking chlorella.

  • Allergic Reactions: Be aware of any potential allergic reactions.

  • Heavy Metal Contamination: Ensure the chlorella supplement is sourced from a reputable manufacturer to avoid heavy metal contamination, which can be harmful during pregnancy.

  • Balanced Diet: Chlorella should not be used as a substitute for a balanced and varied diet. Continue to consume a healthy diet rich in fruits, vegetables, lean proteins, whole grains, and dairy products.

  • Interaction with Medications: Chlorella may interact with certain medications. Discuss all supplements and medications you are taking with your healthcare provider.

  • Immune System Effects: Chlorella is known to stimulate the immune system. Pregnant women with autoimmune conditions should use it with caution and under medical supervision.

  • Quality Assurance: Opt for organic chlorella supplements from trusted manufacturers to ensure product quality and safety.

Conclusion: Is Chlorella Safe During Pregnancy?

In conclusion, while chlorella may offer health benefits for pregnant woman (such as providing high level of nutrients, reducing the risk of anaemia, lowering incidents of edema and proteinuria and enhancing immune function), and is generally considered safe in small to moderate amounts, pregnant women should exercise caution and seek advice from a healthcare provider before incorporating it into their diet. Any adverse effects, such as digestive issues, should prompt immediate consultation with a healthcare professional.

Maintaining a varied and balanced diet remains the best approach to ensure both maternal and pregnancy health. Furthermore, choosing an organic chlorella supplement from a reputable source can help mitigate potential risks. 

Always prioritise professional medical advice to ensure safety!

References and Further Reading:

1. Chlorella pyrenoidosa Supplementation Reduces the Risk of Pregnancy-Associated Anemia and PIH:

Summary:¬†This study investigated the effects of Chlorella on pregnancy anaemia and pregnancy-induced hypertension (PIH) in Japanese women. A total of 70 pregnant women were divided into a control group (n=38) and a Chlorella group (n=32), with the latter receiving 6 grams of Chlorella daily from the 12th‚Äď18th week of gestation until delivery. The Chlorella group had significantly lower rates of anaemia, proteinuria, and edema compared to the control group. The findings suggest that Chlorella is beneficial for reducing the risk of anaemia and PIH during pregnancy.

Authors: Shiro Nakano, Taketoshi Noguchi, Hideo Takekoshi, Go Suzuki, Masuo Nakano.

2. The Effect of Chlorella Supplementation in Pregnant Women with Low-Grade Inflammation:

Summary: This 2023 study published in Food Science & Nutrition evaluated the efficacy and safety of Chlorella supplementation in pregnant women with low-grade inflammation. The study was an open-label, randomised, controlled trial involving 22 pregnant women, divided into a Chlorella group and a control group. The Chlorella group took 6 g/day of Chlorella tablets from 12-18 weeks of gestation until delivery.

Results showed that the Chlorella group had a significantly lower rate of constipation compared to the control group. The study concluded that Chlorella supplementation is beneficial and safe for pregnant women, particularly in reducing constipation and the need for laxatives. The study also noted that Chlorella supplementation did not result in any adverse effects on maternal or newborn health, suggesting its overall safety during pregnancy.

3. Maternal-Fetal Distribution and Transfer of Dioxins in Pregnant Women in Japan, and Attempts to Reduce Maternal Transfer with Chlorella (Chlorella pyrenoidosa) Supplements 

Summary: This 2005 study published in Chemosphere examined the transfer of dioxins from mothers to foetuses and nursing infants. It involved 44 pregnant Japanese women, 23 of whom took Chlorella pyrenoidosa supplements. The study found that dioxin levels in breast milk were approximately 30% lower in the Chlorella group compared to controls, indicating that Chlorella supplements may help reduce maternal transfer of dioxins. This suggests potential benefits of Chlorella supplementation for pregnant women to mitigate dioxin exposure risks to their infants.

Authors: Shiro Nakano, Taketoshi Noguchi, Hideo Takekoshi, Go Suzuki, Masuo Nakano.

4. Potential of Chlorella as a Dietary Supplement to Promote Human Health:

Summary:¬†This 2020 study published in¬†Nutrients¬†explores the health benefits of Chlorella as a dietary supplement. The study highlights Chlorella's rich content of vitamins, minerals, and bioactive compounds, including significant amounts of folate and iron. "In a cohort of 32 women in the second and third trimester of pregnancy, oral Chlorella supplementation (6 g/day) for 12‚Äď18 weeks decreased markers of anaemia as compared to the control group, suggesting that Chlorella supplementation significantly reduces the risk of pregnancy-associated anaemia".

This indicates that Chlorella is considered beneficial during pregnancy, particularly in reducing the risk of anaemia. However, the study emphasises the importance of ensuring product quality to avoid contamination.

Authors: Tomohiro Bito, Eri Okumura, Masaki Fujishima, and Fumio Watanabe

5. Chlorella suppresses methylmercury transfer to the fetus in pregnant mice:

Summary: This 2011 study published in Toxicology investigates the effect of Chlorella supplementation on methylmercury (heavy metal) transfer from pregnant mice to their fetuses. The study found that Chlorella significantly reduced methylmercury levels in the blood, brain, liver, and kidneys of both mothers and fetuses, suggesting that Chlorella can suppress methylmercury transfer and reduce its accumulation.

Authors: Takuya Uchikawa, Isao Maruyama, Shoichiro Kumamoto, Yotaro Ando, Akira Yasutake.

6. Microalgae-based products: Food and public health:

Summary: This 2022 review article published in Future Foods examines the potential of microalgae-based products for food and public health. Microalgae, including species like Chlorella and Spirulina, offer nutritional benefits such as lipids, proteins, and antioxidants. The review discusses the scalability and sustainability of microalgae production, contamination risks, and the necessity of quality control. It emphasises microalgae's role in addressing global food security and environmental challenges while ensuring consumer safety through rigorous monitoring.

Authors: Ana Paula Ferreira de Oliveira, Adriana Pavesi Arisseto Bragotto

Frequently Asked Questions:

Can chlorella improve iron levels during pregnancy?

Yes, chlorella is rich in iron, which can help prevent and manage anemia during pregnancy.  It's advisable to contact a healthcare specialist before supplementing.

Should I choose organic chlorella while pregnant?

Yes, opting for organic chlorella helps ensure the supplement is free from contaminants and additives. It's advisable to contact a healthcare specialist before supplementing.

Can chlorella interact with prenatal vitamins or other medications?

Consult your healthcare provider, as chlorella may interact with certain medications and supplements.

Can chlorella help with pregnancy-related fatigue?

Chlorella's high nutrient content may help improve energy levels and reduce fatigue during pregnancy. It's advisable to contact a healthcare specialist before supplementing.

What should I do if I experience side effects from chlorella during pregnancy?

Discontinue use and consult your healthcare provider immediately if you experience any adverse effects.

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