People recovering from long illness are often advised to include the alga Spirulina in their diet because it

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Spirulina is a blue-green algae. Spirulina platensis is one of the richest source of protein, containing 40-50 percent crude protein on dry weight basis which under favourable condition may reach upto 70 percent. Its protein has balanced composition containing all essential amino-acids and lysine and tryptophan being present in sufficient quantities. Spirulina is also rich in vitamins, particularly Vit. B ₁₂ , which is not common in plant products and contains considerable amounts of fats, carbohydrates and mineral