Dietary Proteins as Determinants of Metabolic and Physiologic Functions of the Gastrointestinal Tract

Dietary proteins elicit a wide range of nutritional and biological functions. Beyond their nutritional role as the source of amino acids for protein synthesis, they are instrumental in the regulation of food intake, glucose and lipid metabolism, blood pressure, bone metabolism and immune function. The interaction of dietary proteins and their products of digestion with the regulatory functions of the gastrointestinal (GI) tract plays a dominant role in determining the physiological properties of proteins. The site of interaction is widespread, from the oral cavity to the colon. The characteristics of proteins that influence their interaction with the GI tract in a source-dependent manner include their physico-chemical properties, their amino acid composition and sequence, their bioactive peptides, their digestion kinetics and also the non-protein bioactive components conjugated with them. Within the GI tract, these products affect several regulatory functions by interacting with receptors releasing hormones, affecting stomach emptying and GI transport and absorption, transmitting neural signals to the brain, and modifying the microflora. This review discusses the interaction of dietary proteins during digestion and absorption with the physiological and metabolic functions of the GI tract, and illustrates the importance of this interaction in the regulation of amino acid, glucose, lipid metabolism, and food intake

The effect of dairy products consumed with high glycemic carbohydrate on subjective appetite, food intake and post-prandial glycemia in older adults

Objective: To compare the effect of liquid, semi-solid and solid dairy products and a non-dairy beverage when consumed with glycemic carbohydrate on subjective appetite, food intake (FI) and post-prandial glycemia (PPG) in healthy older adults. Design: Thirty healthy men and women (14 males and 16 females; age: 64.6 + 2.4 y; BMI: 25.6 + 2.5 kg/m2) participated in a randomized crossover study. Treatments were one of 250 mL of 2% fat milk and soy beverage, 175 g of 2% Greek yogurt and 30 g of Cheddar cheese consumed as part of an isocaloric (380 kcal) meal with bread and jam. Water alone served as the energy-free control for subjective appetite. At 180 min after consumption, the participants were fed an ad libitum meal to measure FI. Subjective appetite, blood glucose and insulin were measured at baseline and at intervals both before (post-treatment) and after the meal (post-meal). Results: Cheese and yogurt resulted in lower post-treatment blood glucose than milk and soy beverage when consumed with carbohydrate (pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The effects of cultured dairy and nondairy products added to breakfast cereals on blood glucose control, satiation, satiety, and short-term food intake in young women

Breakfast cereals are often consumed with dairy products or nondairy alternatives; however, the effect of the combination on blood glucose and food intake control is not well investigated. In a randomized, crossover study, 24 healthy women (age: 22.7 ± 2.5 years; body mass index: 22.1 ± 1.5 kg/m2) consumed, to satiation, 1 of 3 treatments: Greek yogurt with granola (150 kcal, 9.2 g protein, 2.6 g fat, 2.0 g dietary fibre, and 21.5 g available carbohydrate/100 g); cultured coconut product with granola (146 kcal, 3.2 g protein, 3.2 g fat, 5.6 g dietary fibre, and 21.9 g available carbohydrate/100 g); or water control. The data were analyzed with repeated-measures ANOVA. The 2 h blood glucose iAUC was 52% lower after the dairy compared with nondairy treatment (P < 0.0001). While there were no differences in food intake between the caloric treatments consumed to satiation, protein intake was 3 times higher and fibre intake was 4 times lower after the dairy compared with nondairy treatment. Both caloric treatments resulted in similar suppression of ad libitum food intake at 2 h (P < 0.003) and subjective appetite over 2 h (P < 0.0001) compared with water. The cumulative food intake over 2 h was lower after water (P < 0.05). The 1.8-fold increase in postprandial insulin after dairy compared with nondairy treatment may explain the reduction in blood glucose without an increase in subsequent energy intake. Novelty - Blood glucose in young females is lower after a breakfast with granola in a high-protein cultured dairy than when in a high-fibre nondairy cultured product. - Subjective appetite over 2 h and food intake 2 h later was similarly lower after both breakfasts but cumulative intake was higher compared with breakfast skipping.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Role of single serving form of dairy on satiety and postprandial glycaemia in young and older healthy adults

Dairy proteins reduce appetite and improve postprandial glycaemic response in adults. However, there are no reports of dairy in amounts usually consumed on satiety and postprandial glycaemia in either young or older adults. In a randomized crossover design, 30 healthy young adults (age: 23.5 ± 0.5 years; body mass index (BMI): 21.8 ± 0.4 kg/m2) and 30 healthy/overweight older adults (age: 65.2 ± 0.5 years; BMI: 24.7 ± 0.6 kg/m2) consumed 1 serving (according to manufacturers’ labels) of skim milk (0.1% milk fat (MF)), whole milk (3.25% MF), plain Greek yogurt (2% MF), cheddar cheese (31% MF), and water (energy-free control) after a 12-h fast. Subjective appetite was measured every 15–30 min over 3 h. Blood glucose and insulin were measured at baseline and every 15–30 min over 2 h. All dairy treatments reduced post-treatment subjective appetite area under the curve (AUC) over 3 h by 8%–17% more than water. Greek yogurt reduced appetite 3-h AUC more than skim and whole milk by 9% and 7%, respectively (p < 0.0001). Post-treatment blood glucose 2-h AUC was 42% lower in young compared with older adults (p = 0.003). It was also 52%–78% lower after cheese compared with milks and yogurt (p < 0.0001). Post-treatment insulin AUC after cheese was only 10%–15% of that after milks and Greek yogurt (p < 0.0001). We conclude that single servings of dairy differ in effect on postprandial satiety and glycaemia and merit consideration in management of metabolic syndrome.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The effect of dairy and non-dairy beverages consumed with high glycemic cereal on subjective appetite, food intake and post-prandial glycemia in young adults

Objective: To compare the effect of dairy and non-dairy beverages when consumed with carbohydrate at breakfast on subjective appetite, food intake (FI) and post-prandial glycemia (PPG) in healthy young adults. Design: Twenty-six healthy males and females (13 males and 13 females; 23.0 + 2.6 years; BMI: 22.3 + 1.5 kg/m2) participated in a randomized crossover study. They consumed non-isocaloric amounts (250 mL) of almond beverage, soy beverage, 1% fat milk, yogurt beverage and water (control) with cereal and 120 min later, an ad libitum meal. Subjective appetite, PPG and insulin were measured at baseline and at intervals before and after the meal at which FI was measured. Results: Post-treatment blood glucose was lowest following soy beverage compared to all treatments but was not different from milk (p=0.0002). There were no differences between any other treatments. However, over the first hour, PPG for all treatments was 27% lower compared to water (pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Pre- and within meal effects of fluid dairy products on appetite, food intake, glycemia and regulatory hormones in children

The effect of beverages commonly consumed by children in-between or with meals on short-term food intake (FI) and glycemic control has received little attention. Therefore, two experiments were conducted in 9â 14 y old children following a randomized repeated measures design. Experiment 1 (n=32) compared the effects of water (control) and isocaloric (130 kcal) amounts of 2% milk, chocolate milk, yogurt drink and fruit punch on subjective appetite and FI. Experiment 2 (n=20) compared the effects of isocaloric (130 kcal) amounts of 2% milk and fruit punch on subjective appetite, FI, glycemic and appetite hormone responses. One serving of the beverages was given as a pre-meal drink at baseline (0 min) and a second serving 60 min later with an ad libitum pizza meal. Meal FI in Experiment 1 was lower by 14% and 10%, respectively after chocolate milk and yogurt drink (pThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Effect of Commercially Available Sugar-Sweetened Beverages on Subjective Appetite and Short-Term Food Intake in Boys

It is unclear whether sugar sweetened beverages bypass regulatory controls of food intake (FI) in boys. The objective of the present study was to determine the effects of isovolumetric preloads (350 mL) of a fruit-flavoured drink (154 kcal), cola (158 kcal), 1% M.F. chocolate milk (224 kcal), and water (0 kcal) on subjective appetite and FI in boys aged 9&#8315;14 years. On four separate mornings, boys consumed one of the preloads in a random order; subjective appetite was measured at 15 min intervals, and FI was measured via an ad libitum pizza lunch at 60 min post-beverage consumption. In the 32 boys (age: 11.8 &#177; 0.3 years), FI was reduced (p &lt; 0.001) after cola (940 &#177; 46 kcal) and chocolate milk (878 &#177; 41 kcal) compared with the water control (1048 &#177; 35 kcal) and after chocolate milk compared to the fruit drink (1005 &#177; 44 kcal). Cumulative FI after the fruit drink was greater than the water control (1159 &#177; 44 vs. 1048 &#177; 35 kcal; p = 0.03). Average appetite was not affected by the treatment, but the cola treatment resulted in greater fullness (p = 0.04) and lower prospective food consumption (p = 0.004) compared with the fruit drink. In conclusion, chocolate milk and cola suppressed next-meal FI at 60 min, while fruit drink increased cumulative FI (beverage + next meal) over 60 min in boys. Results from this study suggest that beverage composition is an important determinant of FI suppression in boys

Effect of dairy and non-dairy snacks on postprandial blood glucose regulation in 9-14 year old children

In adults, dairy consumption improves short-term blood glucose regulation. It is unknown if these short-term benefits extend to children of different weight statuses. The objective of this study was to investigate the effect of a dairy and nondairy snack in both normal-weight (NW) and overweight/obese (OW/OB) children on blood glucose regulation and food intake (FI). In a repeated-measures crossover design, 11 NW and 7 OW/OB children (age: 9–14 years), consumed, in random order, a dairy (Greek yogurt, 198.9 g, 171 kcal, 0 g fat, 17 g protein) or nondairy (mini sandwich-type cookies, 37.5 g, 175 kcal, 7.5 g fat, 1.3 g protein) snack containing 25 g of available carbohydrates. Ad libitum FI was measured 120 min after snack consumption. Blood glucose, insulin, C-peptide, and glucagon-like peptide-1 (GLP-1) were measured at 0 min (before the snack), and at 30, 60, 90, and 120 min after snack consumption. Insulin secretion was calculated from deconvolution of C-peptide. Hepatic insulin extraction was calculated as C-peptide divided by insulin. FI did not differ between snacks (P = 0.55). Mean blood glucose was lower (P < 0.001) and insulin higher (P < 0.0001) in the 120 min after consuming the dairy snack. C-Peptide concentrations (P = 0.75) and insulin secretion (P = 0.37) were not different between snacks. The increase in insulin was explained by reduced hepatic insulin extraction (P < 0.01). Consumption of the dairy snack also increased mean GLP-1 concentrations (P < 0.001). In conclusion, consumption of a dairy snack by NW and OW/OB children results in reduced postprandial blood glucose concentrations and elevated circulating insulin compared with a nondairy snack possibly because of delayed hepatic insulin extraction.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author