Utilization of Algae as a Protein Source for Humans

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Abstract
Two experiments were conducted using algae as the principle source of nitrogen for human subjects. This represented approximately 90 to 95% of the total nitrogen intake. In the first experiment Scenedesmus obliquus, 7.1 g N/day, was fed as the whole green lyophilized algae. At the end of 5 days the mean nitrogen balance for 5 subjects was +0.20 g N/day. In the second experiment, using 5 different subjects, 2 levels of ethanol-extracted Chlorella pyrenoidosa were fed (6.0 and 10.0 g N/day), each for 10 days. The mean nitrogen balance for 6.0-g algae nitrogen was negative, 0.84 g N/day, whereas the mean nitrogen balance for 10.0-g algae nitrogen level was positive, 0.61 g N/day. High fecal excretion of nitrogen was characteristic of all levels of algae. As a result, the algae used in these studies had low apparent nitrogen digestibility, 68% for dried green Scenedesmus obliquus and 58% for ethanol extracted Chlorella pyrenoidosa. This apparent digestibility was the major contributing factor to positive or negative nitrogen balance. The second experiment demonstrated that human subjects were capable of consuming algae as the principle source of protein in the diet for a 20-day period without ill effect.