Protein and amino acid digestibility of15N Spirulina in rats

Purpose Spirulina is often used as dietary supplement for its protein content and quality. However, in vivo data on protein digestibility are lacking. This study aims to determine nitrogen and amino acid digestibility in rats. A secondary objective was to test the effect of sonication prior to ingestion to break cell walls. Methods Wistar rats were fed a single test meal containing(15)N Spirulina that was either sonicated (n = 11) or not (control,n = 13). Rats were euthanized 6 h after the meal ingestion. Spirulina nitrogen digestibility was measured by assessment of(15)N recovery in digestive contents. Amino acid digestibility was measured by quantification of the caecal amino acid content and their(15)N enrichment. Results Real fecal nitrogen digestibility was 86.0 +/- 0.7%, without any differences between groups. Mean(15)N amino acid caecal digestibility was 82.8 +/- 1.3%, and values ranged between 77.9 +/- 1.9% for serine and 89.4 +/- 1.0% for methionine. No effect of sonication was observed. The most limiting AA was histidine, with a chemical score of 0.98 and a PD-CAAS of 0.84. Lysine was also limiting in a lesser extent. Conclusion The nitrogen and amino acid digestibility of Spirulina is relatively low, and showed no effect of prior sonication. Its amino acid composition is relatively well balanced but not enough to compensate for the poor digestibility.

Automated summary

This study aimed to determine nitrogen and amino acid digestibility in rats fed with Spirulina, and also to test the effect of sonication on breaking cell walls. The results showed that the digestibility of nitrogen and amino acids in Spirulina was relatively low, with no significant effect of prior sonication.