The supplement called spirulina consists of one or more members of a family of blue-green algae. The name was inspired by the spiral shapes in which these plants array themselves as they grow. 1 Other blue-green algae products are also available on the market, and they are discussed in this article as well.

Spirulina grows in the wild in salty lakes in Mexico and on the African continent. It reproduces quickly, and because the individual plants tend to stick together, it is easy to harvest. Records of the Spanish conquistadors suggest that the Aztecs used spirulina as a food source; we also know that the Kanembu people of Central Africa harvested it from what is now called Lake Chad.

This plant contains high levels of  various B vitamins, beta-carotene , other carotenoids, and minerals, including calcium , iron , magnesium , manganese , potassium , and zinc . It is also a source of gamma-linolenic acid (GLA) . Spirulina is a rich source of protein—dried spirulina contains up to 70% protein by weight 2 —but you'd have to eat an awful lot of spirulina capsules to obtain a significant amount of protein this way. Spirulina also contains vitamin B 12 , a nutrient otherwise found almost exclusively in animal foods. However, there's a catch: the B 12 in spirulina is not absorbable. 3

Spirulina has not been proven effective for any medical condition, and there are significant safety concerns involving all forms of blue-green algae (see Safety Issues ).

Requirements/Sources

Unless you live within 35 degrees of the equator and on the shores of an alkaline lake, you will have difficulty finding spirulina anywhere but in a health food store. Most carry a number of brands of spirulina that has been dried and processed into powder or tablets.

Therapeutic Dosages

Researchers studying spirulina's effects on health have used a variety of doses, ranging from 1 to 8.4 g daily.

Therapeutic Uses

There is no question that spirulina is a nutritious food, but it isn't cheap. 4 Protein can be obtained much more easily and inexpensively from legumes, nuts, grains, and animal foods; iron from dark greens, prunes, and meat; and carotenes and vitamins from standard fruits and vegetables.

Spirulina might have other specific therapeutic uses beyond general nutritional support, but the evidence supporting these recommendations is highly preliminary at best.

Manufacturers of spirulina supplements sometimes claim that the plant can reduce appetite, thereby helping overweight individuals control their food intake. However, one small double-blind study of spirulina for weight loss failed to find a significant difference between spirulina and placebo treatment. 5

One small double-blind trial did find evidence that a blue-green algae called Chlorella pyrenoidosa might be useful for fibromyalgia . 6

It is commonly stated that spirulina and related products can enhance immunity . 15-17 However, most of the evidence supporting this statement is too weak to mean much; the one meaningful trial, a double-blind study of 124 healthy adults, failed to find that chlorella supplements enhanced the immune response to influenza vaccine. 37

Evidence from animal studies, preliminary human trials and one small double-blind, placebo-controlled study suggests that spirulina or other forms of algae might improve cholesterol profile. 7-9,38

Very preliminary evidence hints that spirulina may help prevent cancer . 10-12

Test tube and animal studies suggest that spirulina might have some activity against the HIV, but much more research needs to be done before we could say that spirulina is helpful against HIV infection . 13,14

Highly preliminary evidence suggests that spirulina or other blue-green algae products may counter allergic reactions, such as hay fever and hives , 18,19,39,40 help protect the liver from toxic chemicals, 20,21 reduce blood pressure , 22 and control symptoms of ulcerative colitis .

Despite widespread publicity, there is no evidence that spirulina is useful for attention deficit disorder .

What Is the Scientific Evidence for Spirulina?

There are no well-documented uses of spirulina.

Fibromyalgia

Fibromyalgia is a common chronic condition whose main symptoms are specific tender points on various parts of the body, widespread musculoskeletal discomfort, morning stiffness, fatigue, and disturbed sleep. The cause of fibromyalgia is not known, and current treatments are far from completely satisfactory.

A recent study suggests that the nutritious algae Chlorella pyrenoidosa might be helpful. 23 In this double-blind, placebo-controlled trial, 37 people with fibromyalgia were given either placebo or chlorella supplements at a dose of 10 g daily. At the end of 3 months, individuals were switched to the opposite group, and then treated for an additional 3 months. The results showed significant improvements in symptoms when participants used chlorella as compared to placebo.

Weight Loss

A double-blind, placebo-controlled trial investigated the possible weight loss effects of spirulina. 24 However, while individuals taking 8.4 g of spirulina daily lost weight, the difference between the spirulina group and the placebo group was not statistically significant . Larger and longer studies are needed to establish whether spirulina is indeed an effective treatment for obesity.

Safety Issues

Spirulina itself appears to be nontoxic. 25 Studies in rats showed that high spirulina intake caused no weight reduction or toxicity symptoms in rats, nor did spirulina affect the rats' ability to reproduce normally. 26,27

Nevertheless, there are areas of serious concern for consumers.

Various forms of blue-green algae can be naturally contaminated with highly toxic substances called microcystins. 30,31,35

Some states, such as Oregon, require producers to strictly limit the concentration of microcystins in blue-green algae products, but the same protections cannot be assumed to have been applied to all products on the market. Furthermore, the maximum safe intake of microcystins is not clear, and it is possible that when blue-green algae is used for a long time, toxic effects might build up. Long-term use by children raises particular concerns, especially in light of the widely popularized, but unsubstantiated belief, that blue-green algae is useful for attention deficit disorder.

Blue-green algae can also contain a different kind of highly toxic substance, called anatoxin. 36

In addition, when spirulina is grown with the use of fermented animal waste fertilizers, contamination with dangerous bacteria could occur. 28,32 There are also concerns that spirulina might concentrate radioactive ions found in its environment. 29 Probably of most concern is spirulina's ability to absorb and concentrate heavy metals such as lead and mercury if they are present in its environment. One study of spirulina samples grown in a number of locations found them to contain an unacceptably high content of these toxic metals. 33 However, a second study on this topic claims that the first used an unreliable method of analyzing heavy metal content, 34 and concludes that a person would have to eat more than 77 g daily of the most heavily contaminated spirulina to reach unsafe mercury and lead consumption levels.

These researchers, however, go on to suggest that it is not prudent to eat more than 50 g of spirulina daily. The reason they give is that the plant contains a high concentration of nucleic acids, substances related to DNA. When these are metabolized, they create uric acid, which could cause gout or kidney stones. This is of special concern to those who have already had uric acid stones or attacks of gout.

The safety of spirulina in pregnant and nursing women, young children, and individuals with kidney or liver disease has not been determined.