Impact of aging on the digestive system related to protein digestion in vivo

“…Morales-Suárez-Varela et al. 2011) and the prevalence of being edentulous, i.e. lacking all teeth, ranges between 4 and 56% across studies (Table 2(a)) with age ranges of 65–92 years (Choufani et al. 2020; Ikebe et al. 2007; Saunders and Friedman 2007; Shariff et al. 2018; Ramsay et al. 2015).”

“A smaller particle size, and thus an increased surface area, has been shown to result in an increase in protein digestion of up to 10% in vitro and in pigs (Healy et al. 1994; Lyu et al. 2022; Wondra et al. 1995; Zahir, Fogliano, and Capuano 2018).”

“Small bowel bacterial overgrowth increases with aging (18–80 years) along with concomitant diseases (Mitsui et al. 2006; Leite et al. 2022; Lewis et al. 1999; Parlesak et al. 2003).”

“Aging does not induce changes in the size and surface of neurons in the intestinal ganglia, but it decreases the number of neurons, by 16.5% in one study (Mandić et al. 2013) and by 25.9% in another (Mandic et al. 2016) with both populations aged 20–84 years.”

“Intestinal wall integrity is found to be decreased (Hendriks et al. 2021) and permeability increased with low-grade inflammation present (Valentini et al. 2014), but that result is not consistently found (Saltzman et al. 1995).”

“…Morales-Suárez-Varela et al. 2011) and the prevalence of being edentulous, i.e. lacking all teeth, ranges between 4 and 56% across studies (Table 2(a)) with age ranges of 65–92 years (Choufani et al. 2020; Ikebe et al. 2007; Saunders and Friedman 2007; Shariff et al. 2018; Ramsay et al. 2015).”

“Moreover, a 57% decreased presence of Brunner’s glands that produce alkaline fluid was observed (Nandagopalan, Magdalene, and Binu 2014).”

“…and Lang 1994; Robbins, Bridges, and Taylor 2006), caused by changed sphincter contractility and pressure (Cock and Omari 2018; Bardan et al. 2000; Besanko et al. 2014), and muscular and neuronal changes (Milosavljevic et al. 2013; Meciano Filho, Carvalho, and de Souza 1995; Iida et al. 2013).”

“Median particle size was also found to be larger in older adults (average 72 years) compared to young (average 24 years) (Ketel et al. 2021).”

“Another, smaller study (Atallah et al. 2022) yielded a comparable result, no significant age effect on oro-cecal digestibility between young (2 months) and middle-aged (11 months) rats with either normal or high adiposity for a highly digestible casein.”

“…1997; Ortega, Martín, and Clavé 2017; Clavé and Shaker 2015; Muhle et al. 2015), affects the elderly with a prevalence ranging from 13.8 to 70% (Watanabe et al. 2021; Yoshikawa et al. 2005; Smith et al. 2006; Nilsson et al. 1996; Leder and Suiter 2009; Kawashima, Motohashi, and Fujishima 2004).”

“Moreover, acid secretion-related organelles in parietal cells do not degenerate with aging, and expression of H + /K + ATPase may even increase (Zhang et al. 2013).”

“Concerning structure, there is increased fibrosis in the pancreas (Saini et al. 2015; Löhr et al. 2018) and increased fat content (Yang et al. 2019; Moin et al. 2020).”

“The muscular layer of different parts of the stomach has been investigated and showed stiffer muscles in participants aged 65–95 years (Azuma et al. 2004 e. small intestine is therefore expected that the mixing of the chyme with acid and digestive enzymes is decreased.”

“This can be partly explained by reduced chewing efficiency — determined by bite force, number of teeth, number of chewing cycles before swallowing, and the food particle size distribution — as well as reduced gastric acid secretion and slower gastric emptying [121].”

“Gastric chyme then undergoes further breakdown and hydrolysis in the intestine, with subsequent absorption of amino acids and peptides (Hinssen et al. 2024 ).”

“Host-derived polyamines maintain systemic and intracellular pools essential for basal cellular functions, including proliferation, differentiation, and tissue maintenance, while dietary polyamines absorbed primarily in the upper gastrointestinal tract, support circulating and tissue-associated…”