What are the Different Chlorella Side Effects?

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  • Written By: Christine Gray
  • Edited By: A. Joseph
  • Last Modified Date: 02 September 2019
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Chlorella, also known as sun chlorella or green algae, is a dietary supplement made from single-celled freshwater algae. Supplement manufacturers most commonly use the Chlorella pyrenoidosa or Chlorella vulgaris species. The most common chlorella side effects are diarrhea, nausea, gas, abdominal cramping and green discoloration of the stool. Allergic reactions are possible side effects of chlorella for some people.

Proponents claim that chlorella is an an effective treatment for cancer and viral and bacterial infections. They also claim that it boosts immune function, lowers blood pressure and cholesterol levels, treats gastrointestinal disorders and detoxifies the body. There has been very little clinical research regarding chlorella, however. Chlorella side effects are usually mild, but some people experience reactions severe enough to merit discontinuing use.

For users who experience them, chlorella side effects most often present during the first week of use. Approximately one-third of users experience gastrointestinal distress severe enough to discontinue use of chlorella. Photosensitivity, or an unusual sensitivity to sunlight, is another of the possible side effects of chlorella. It may be necessary for someone taking chlorella to wear sunblock during sun exposure, especially if he or she is light-skinned.


It's possible for some people to be allergic to the algae itself, but chlorella supplements can contain iodine, which can also cause reactions. Symptoms of an allergic reaction to chlorella include asthma and difficulty breathing. A reaction to the iodine can cause itching, hives, swelling, tightness of breath, vomiting and diarrhea. If symptoms appear, the person should discontinue its use and seek medical treatment.

Both immunocompromised individuals and those with autoimmune diseases can also experience chlorella side effects. Chlorella use might encourage dangerous bacterial growth in the intestines of immunocompromised users. Those who have autoimmune diseases, on the other hand, might experience a flare in disease activity related to chlorella's purported immune-boosting effects. Chlorella might also reduce the effectiveness of immunosuppressant medications.

Chlorella contains a high concentration of vitamin K, which plays a role in blood clotting. Chlorella might reduce the effectiveness of blood-thinning medications. One should consult a physician before taking chlorella if he or she has been prescribed blood-thinning medications.

Research has shown evidence to suggest that chlorella offers some cancer-fighting benefits. A protein extracted from chlorella has been shown to work prophylactically against the spread of cancer cells in mice. In mice, the same extract has been shown to reduce the side effects of chemotherapy drugs without reducing the drugs' effectiveness.


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Post 12

Where is a source that says it sensitizes your skin to the sun? That could do a lot of damage!

Post 9

For the person who wants to lower their blood pressure, I know exactly how to do it easily: my FAR sauna. I have a portable one and it's crazy, but my already normal BP is even lower.

It's the heating up of your blood that makes everything flow better, including to the heart.

Post 6

I think one should also be extremely worried about contamination of the algae with toxic heavy metals, like lead, and such, since chorella is noted for it's ability to soak up and absorb toxins.

So, make sure the place you buy it from is willing to show you their lab certificate, saying that it's toxin free.

Post 5

I immediately experienced gas and abdominal pain.

Post 4

I really wanted to try chlorella for the boost to my immune system but was unfortunately one of the people that were quite allergic to this form of green algae.

I have pretty bad asthma and after taking chlorella I found my symptoms flaring up and it was difficult to breathe. I had to go to my doctor and she made me stop taking the supplements I had purchased.

I complained to her that I was always getting sick and needed to somehow boost my immune system so she recommended more exercise and lots of vitamins. We'll see how the supplements she gave me work, and I suggest if you want to try chlorella that you make sure you aren't allergic to it before going full steam ahead with the supplements.

Post 3

Does anyone have any experience with taking chlorella for high blood pressure or for help with their cholesterol?

I have issues with both high blood pressure and raised levels of bad cholesterol in my blood and am looking for a natural product that could help me improve my condition.

Green algae seems like a good choice from the reviews I have read online but I worry about all the side effects I have seen listed here.

Do you think it is safe to take chlorella? Or do you think that the side effects happen to often for it to really be considered safe?

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