Bone Abstracts

New food strategies should be developed to fight against child malnutrition and growth retardation in developing countries. Spirulina alga, one of the richest sources of vegetable protein, contains all essential amino acids. It easily grows in tropical regions. We hypothesized that impaired peak bone mass acquisition (PBMA) caused by dietary protein deficiency could be prevented by Spirulina supplementation in growing rats.

One-month old female rats were fed an isocaloric diets containing 10% casein (Con10), 5% casein (Con5) or 5% casein +5% Spirulina (Con5+Spi5) during 8 weeks. Cortical and trabecular bone microstructure were analyzed by microCT and areal BMD by DXA. Bone strength was evaluated by tibia midshaft three-point binding test and proximal tibia compression test. Serum IGF1 was measured.

As compared with the Con10 group, isocaloric low-protein diet decreased proximal tibia areal BMD (−10%, P<0.0001), bone trabecular volume (BV/TV; −41% P<0.01) and trabecular thickness (Tb.Th; −10%, P<0.05), resulting in a lower ultimate strength (US; −18%, P<0.01). All these parameters were significantly higher in the Con5+Spi5 group which showed similar values as the Con10 group. In tibia cortical middiaphysis, there was a trend towards lower values (areal BMD: −4%, P<0.056, cortical bone volume (Ct.BV): −7%, P=0.063, and US: −7%, NS) while Con5+Spi5 group showed significant higher cortical bone parameters than Con5 group (areal BMD: +6%, P<0.05; Ct.BV: +12%, P<0.01; US: +10% NS). Serum IGF1 was also lower in the Con5 group compared to Con5+Spi5 and Con10 groups (380.5±10.1; 437.0±12.4 and 437.9±18.5 ng/ml respectively; P<0.05).

We demonstrate that Spirulina supplementation effectively prevents cortical and trabecular bone alterations, as well as bone strength decrease induced by isocaloric dietary protein deficiency during growth, in association with the maintenance of optimal IGF1 levels. Spirulina is an effective nutrient to prevent impaired PBMA in protein deficient growing rats.