Blue-green algae are microscopic plants which are more closely akin to bacteria than to seaweed. The popular blue-green algae, spirulina, is currently cultivated and harvested on an industrial scale in the ocean and lakes of several countries. It is commonly sold as a general nutritional supplement or weight-loss agent.

Spirulina (including Spirulina maxima and S. platensis) contains a variety of nutrients, such as protein, a variety of B vitamins and minerals, the antioxidants beta-carotene and vitamin E, and phycocyanin.

What It Doesn’t Do

Claims abound that spirulina can be used to successfully treat various medical conditions, such as asthma, depression, digestive problems, fatigue, HIV infection, hypertension, skin disorders, stress, and attention deficit disorder. In addition, it is claimed to improve memory, boost immunity, protect the liver, boost energy levels, and detoxify the body. However, there is no scientific evidence to support any of these claims. In fact, marketers of blue-green algae were recently asked to stop making false health claims.

Although spirulina is commonly marketed as an appetite suppressant, there is no evidence that it is successful in weight-reduction plans.

Over all, there is no strong evidence at present that spirulina can actually treat or cure any illness.

What It Does Do

Phycocyanin, the nontoxic, blue pigment in spirulina, can act as a free radical scavenger and a powerful antioxidant. Studies have shown that phycocyanin can exert a wide range of anti-inflammatory effects, accelerate wound healing, and may help in the healing of ulcers. A heaping tablespoon of spirulina provides about 100 milligrams of phycocyanin.

Phycocyanin is used in the food and beverage industry as a natural blue coloring agent. It is used in sweets, soft drinks, health drinks, chewing gum, ice cream, and other desserts, as well as cosmetics.

There is data showing that spirulina possesses some anti-viral and antitumor properties. Preliminary animal data also suggests it may be useful as a lipid-lowering agent.

Dosage and Precautions

Blue-green algae is typically sold in tablet, capsule, or powder form. It is safe to use when consumed in recommended doses of 1-2 grams three times a day. Side effects are few but may
include skin reactions, nausea, or upset stomach; and allergies to the algae are known.

Because of its high nucleic acid content, excessive consumption of spirulina may increase blood uric acid to undesirable levels. Due to the high iodine content of spirulina, patients with thyroid conditions should not use spirulina as it may decrease the action of
thyroid hormone.


It can’t do everything, but it is a good source of a variety of nutrients, possesses some antiviral and antitumor properties, can act as a powerful antioxidant, and may help in the healing of wounds and ulcers.

Winston J. Craig, Ph.D., R.D., is professor of nutrition at Andrews University in Berrien Springs, Michigan.

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