Poster Topical Area: Energy and Macronutrient Metabolism
Location: Hall D
Poster Board Number: 444
Objectives: Spirulina is often used as a dietary supplement. Protein bioavailability seems to be relatively low but there are little in vivo studies. Our study aimed to measure in vivo the digestibility of spirulina protein and amino acids (AA) and to determine whether it can be improved by sonication.
Methods: Twelve males Wistar rats received a single meal containing 0.77g of spirulina (0.44g of protein) intrinsically labeled with 15N. Six rats were given spirulina that was sonicated for 1.5h and 6 were given untreated spirulina. Rats were euthanized 6h after meal ingestion and gastrointestinal contents (stomach, small intestine, ileum, caecum, and colon) were collected. Digestibility of spirulina protein was determined by measurement of nitrogen and 15N enrichment in gastrointestinal contents by an elementary analyzer coupled to an isotopic ratio mass spectrometry (IRMS). In order to determine amino acid digestibility, amino acids were measured by HPLC and theirs 15N enrichments were measured by gas chromatography – combustion – IRMS. Digestible indispensable amino acid score (DIAAS) was calculated as follow: DIAAS % = 100 x [(mg of digestible dietary IAA in 1g of the dietary protein)/(mg of the same dietary IAA in 1g of the reference protein)]. Results are expressed as mean ± sem and compared by a t test (P<0.05).
Results: Six hours after ingestion, most of dietary nitrogen was found in the caecum and the colon. Oro-fecal digestibility of untreated spirulina was low (81.8±1.8%). Sonication tended (P=0.08) to improve it (86.9±1.8%). Amino acid digestibility varied from 76.5±2.1% for glycine to 90.5±1.2% for methionine. There was no effect of sonication on AA digestibilities. DIAAS calculation shows that spirulina is only marginally limiting in lysine (0.98±0.02). For the other indispensable amino acids, DIAAS score was superior to 1.
Conclusions: This study shows that spirulina have a low digestibility compared to other protein that were evaluated in the same conditions. Based on amino acids measured, spirulina satisfies the requirements in amino acids. Prior sonication only tended to improve spirulina digestibility. Data on additional animals are currently collected to confirm or not this trend.
UMR PNCA, INRA, AGROAPRISTECH
paris, Ile-de-France, France