The Harmful Effects of Chlorella & Spirulina

By Kelsey Gray

The term "algae" is used loosely to describe an unrelated groups of microorganisms that perform photosynthesis. Algae has been used in many forms all over the world in food, cosmetics, fertilizer and paints. and it is the primary ingredient in natural supplements such as chlorella and spirulina.

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Chlorella is a type of freshwater green algae. Most of the chlorella found in the United States is grown in Japan or Taiwan and is processed and turned into tablets or liquid extracts. Before chlorella can be digested by people, its cell walls must be broken down. From this form, chlorella is used as a source of protein, fats, fiber, minerals and vitamins. It is used for treatment of many different illnesses, from preventing cancer, treating ulcers — both intestinal and skin — and reducing cholesterol, among countless other uses.


Spirulina is a large group of blue-green algae found in saltwater and large freshwater lakes. They are typically found in tropical or subtropical waters with a high salt content. Some types of spirulina are cultivated. and some are grown naturally. It is a source of B vitamins, iron and dietary protein. Its uses are varied: weight loss, for attention deficit-hyperactivity disorder, hay fever, diabetes, stress and fatigue.

Side Effects

Because both chlorella and spirulina are supplements, the U.S. Food and Drug Administration (FDA) does not regulate them before they reach the market. Consequently, any side effects chlorella and spirulina might have are not regulated under the FDA, and little independent, clinical research has been done on the possible side effects. According to WebMD, chlorella is not recommended for anyone pregnant or breastfeeding because its effects are not known. Common side effects include diarrhea, nausea, gas, green discoloration of the stools and stomach cramping.

Like chlorella, not enough is known about the effects of spirulina to be recommended for anyone pregnant or breastfeeding. Blue-green algae should be safe as long as it is not contaminated; contaminated spirulina can cause liver damage, weakness, vomiting, rapid heartbeat, shock and possibly death. In addition, spirulina could cause the auto-immune system to become overactive and so should be avoided in the case of auto-immune diseases.