Hydrolyzed collagen (gelatin) decreases food efficiency and the bioavailability of high-quality protein in rats

Abstract

A B S T R A C T ObjectiveAlthough deficient in all indispensable amino acids, gelatin is used in protein-restricted diets. Food efficiency and protein quality of casein and gelatin mixtures in low protein diets in Wistar rats were investigated. MethodsThe rats were treated with protein-restricted diets (10.0 and 12.5%) containing casein (control diets), casein with gelatin mixtures (4:1 of protein content), and gelatin as sources of protein. The food conversion ratio, protein efficiency ratio, relative and corrected protein efficiency ratio, true protein digestibility, and hepatic parameters were estimated. ResultsAfter 28 days of the experiment, food efficiency of 10.0% casein/gelatin diet decreased when compared to that of 10.0% casein diet, and the protein efficiency ratio of the casein/gelatin mixtures (10.0%=2.41 and 12.5%=2.03) were lower than those of the casein (10.0%=2.90 and 12.5%=2.32). After 42 days of the experiment, the weight of the liver of the animals treated with 10.0 and 12.5% casein/gelatin diets, and the liver protein retention of the 12.5% casein/gelatin diet group of animals were lower than those of the control group. ConclusionGelatin decreases food efficiency and high-quality protein bioavailability in protein-restricted diets.Keywords: Amino acids. Biological availability. Caseins. Gelatin. Proteins. Rats. I N T R O D U C T I O NGelatin is a soluble mixture of polypeptides produced by the partial hydrolysis of collagen 1 .Collagen is an insoluble protein of animal origin that holds organs and tissues together and gives strength to tendons, among other biological functions 2,3 . In nutritional terms, gelatin is an incomplete protein because its amino acid profile is quite atypical and deficient in all of the indispensable (essential) amino acids recommended by the Food and Nutrition Board of the Institute of Medicine (IOM) of the National Academy of Sciences 4 . It is known that gelatin contains no tryptophan 5,6 .Gelatin and collagen hydrolysate have been shown to improve skin hydration, transepidermal water loss, elasticity, and skin barrier dysfunction 7,8 . Furthermore, they have been used to promote weight loss because studies have shown that gelatin can inhibit appetite and promote satiety 9,10 . However, the use of gelatin in a protein-restricted diets (like those before and after gastrointestinal tract surgery, chronic renal insufficiency treatment diets, and those aimed to promote weight loss 11,12 ) could be a potential nutritional risk. Insufficient protein intake (in terms of both quantity and quality) inhibits endogenous metabolism of proteins, prolongs the inflammatory phase of the healing process, decreases fibroblast proliferation, angiogenesis and collagen synthesis, and impairs tissue repair 12 . Therefore, the use of gelatin in a protein-deficient diet could slow patient recovery.Considering the uses of gelatin in proteinrestricted diets, this study investigated food efficiency and protein quality of casein (a complete protein) and gelatin mixtures in low protein diet...