A recommended amount of hydrolyzed protein improves physiological function by regulating gut microbiota in aged mice

Dietary proteins play a critical role in maintaining the health of elderly people. Although experts recommend that elderly people consume more protein, a high-protein diet may add to the burden of elderly people with degraded digestion and absorption functions. The effects of a normal or high-protein diet and those of a whole or hydrolyzed protein diet on bone and muscle health and gastrointestinal function were evaluated in aged female C57BL/6J mice. The hydrolyzed protein diet with 14.7% protein energy ratio (HNP) contributed to the maintenance of weight and an increase in bone and muscle mass. Further, the overall aging situation was improved by the consumption of this diet. However, the hydrolyzed protein diet with 21.3% protein energy ratio (HHP) increased the levels of LPS, IL-6, IL-10, and TNF-α in serum. Additionally, the small intestine structure was damaged, and the goblet cell number was decreased in the HHP and whole protein with 21.3% protein energy ratio (HP) groups. The relative abundances of Streptococcus and Peptococcus were decreased while that of Bifidobacterium was increased in HNP group compared with the whole protein with 14.7% protein energy ratio (NP) and HP groups. Undigested proteins entering the intestine may cause undesirable changes in gut microbiota, which adversely affect the aging body in NP and HP groups. In summary, hydrolyzed proteins are more advisable than untreated dietary protein in aged mice. This study aimed to provide guidance for daily diet for elderly people, and provide additional information to industry in order to guide their future food development.