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Spirulina: our future’s green?

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Known as ‘spirulina’, the blue-green cyanobacterium’s official name is Arthrospira platensis. Harvested for food since ancient times, it was first described in 1940 by Dr Dangeard, a French algae expert. He studied a sample that came from French Equatorial Africa, near present-day Chad, where the bacteria, known as dihe, were collected from mats floating on small lakes, dried and broken up into biscuit-sized pieces for sale in the local markets (Microbiol Rev, 1983; 47: 551-78; Perry J et al. Microbial Life. Sunderland, MA: Sinauer Associates, Inc., 2002: 768).

The Spanish conquistadors found a similar species, A. maximus, harvested from Lake Texcoco by the Aztecs, whose city Tenochtitlan was razed to the ground by the Spaniards. The blue-green ooze was collected with fine fishing nets and incorporated into bread. The local word for it was tecuitlatl, which meant ‘stone’s excrement’.

These two instances are the only recorded observations of humans using microbial biomass for food consumption, apparently from time immemorial.

Spirulina derives its energy from sunlight and uses carbon dioxide as its carbon source (Perry J et al., op. cit.). Its minerals are derived from inorganic sources in the environment. It thrives in shallow alkaline ponds and lakes, where the pH is alkaline and the salt (alkaline) concentration (usually sodium carbonate and bicarbon-ate) is high, up to 30 g/L-an environment that is inhospitable to most other organisms. Arthrospira platensis is also prodigious in its production of oxygen.

Spirulina is rich in easily digested protein and phytochemicals. The protein is considered a complete protein, as it contains all the essential amino acids. With a dry mass of around 65-per-cent protein, A. platensis is superior to all other plant sources for protein, nearly attaining the nutritional content of meat.

The environmental and economic benefits of growing spirulina can readily be seen compared with primary agricultural crops. These cyanobacteria can be obtained in high yields with minimal growth require-ments. Kilogram for kilogram of protein, it takes 30 times more water to raise beef than to grow A. platensis, and roughly eight times more to grow maize, soybeans or eggs (Moorhead K, Morgan H. Spirulina: Nature’s Superfood. San Juan, PR: Nutrix Inc., 1995).

Simple volume is not the only consideration. Beef requires fresh water, whereas A. platensis can be grown in brackish or recycled water. Space considerations are also striking. In terms of kilograms of protein produced per hectare, spirulina is 100 times more produc-tive than beef, and more than 10 times more productive than maize or soybeans. In addition, A. platensis can be cultivated on infertile land, while other agricultural crops have more stringent requirements. Yet another advantage is that it’s easily harvested, filtered and washed. In contrast, the disadvantages with traditional agricultural crops include soil erosion, and the toxic environmental effects of pesticides, herbicides and fungicides, which play no part in the production of spirulina. Furthermore, spirulina is also full of important phytochemicals.

Only recently has it gained the attention of medical researchers, with studies showing that A. platensis possesses anti-viral, anticancer, antimicrobial and anti-inflammatory activities (Curr Pharm Biotechnol, 2005; 6: 373-9). It also has beneficial effects in controlling cholesterol, diabetes, coronary artery disease, weight loss and wound-healing. In a 16-week study in Bangladesh, where the water contains high levels of arsenic, 250 mg of spirulina (plus 2 mg of zinc) twice a day resulted in significant improvement in symptoms of chronic arsenic poisoning vs a placebo (Clin Toxicol [Phila], 2006; 44: 135-41).

So, is this ancient organism a cure for our modern ailments? Could this micro-organism help to feed a hungry world where arable land and fresh water are becoming more and more scarce? The world’s popu-lation will soon grow to nine billion, requiring double the current food production using only half the area now available to agriculture. As scientists learn more about the benefits of spirulina, it’s likely that this bright blue-green bacterium will become increasingly important as a food and health supplement. Perhaps we won’t need to rely on the purveyors of genetically modified foods after all.

Harald Gaier

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