G. Harvey Anderson

Whey Proteins in the Regulation of Food Intake and Satiety

Whey protein has potential as a functional food component to contribute to the regulation of body weight by providing satiety signals that affect both short-term and long-term food intake regulation. Because whey is an inexpensive source of high nutritional quality protein, the utilization of whey as a physiologically functional food ingredient for weight management is of current interest. At present, the role of individual whey proteins and peptides in contributing to food intake regulation has not been fully defined. However, Whey protein reduces short-term food intake relative to placebo, carbohydrate and other proteins. Whey protein affects satiation and satiety by the actions of: (1) whey protein fractions per se; (2) bioactive peptides; (3) amino-acids released after digestion; (4) combined action of whey protein and/or peptides and/or amino acids with other milk constituents. Whey ingestion activates many components of the food intake regulatory system. Whey protein is insulinotropic, and whey-born peptides affect the renin-angiotensin system. Therefore whey protein has potential as physiologically functional food component for persons with obesity and its co-morbidities (hypertension, type II diabetes, hyper- and dislipidemia). It remains unclear, however, if the favourable effects of whey on food intake, subjective satiety and intake regulatory mechanisms in humans are obtained from usual serving sizes of dairy products. The effects described have been observed in short-term experiments and when whey is consumed in much higher amounts.

TOTAL PARENTERAL NUTRITION AT HOME: STUDIES IN PATIENTS SURVIVING 4 MONTHS TO 5 YEARS

Total parenteral nutrition at home has been delivered to 12 patients surviving for periods ranging from 4 months to 5 years. The route used is a silicone rubber catheter introduced into the superior vena cava. The mean survival of uncomplicated catheters is 15.8 months, but in 4 patients it is in excess of 28 months. The delivery system is a simple pneumatic infusor set, portable and safe to use, and not requiring complicated electronics. All patients have maintained ideal body weight and have been socially rehabilitated, with two exceptions. Detailed metabolic studies are presented and the data include routine biochemical analyses, liver function tests, liver biopsy results, blood aminograms, the plasma phospholipid fatty acid pattern, the plasma lipoprotein pattern, and blood vitamin and trace element profiles. Based on these findings a nutrient program is recommended and discussed.

Effect of premeal consumption of whey protein and its hydrolysate on food intake and postmeal glycemia and insulin responses in young adults.

BACKGROUND Dairy protein ingestion before a meal reduces food intake and, when consumed with carbohydrate, reduces blood glucose. OBJECTIVE The objective was to describe the effect of whey protein (WP) or its hydrolysate (WPH) when consumed before a meal on food intake, pre- and postmeal satiety, and concentrations of blood glucose and insulin in healthy young adults. DESIGN Two randomized crossover studies were conducted. WP (10-40 g) in 300 mL water was provided in experiment 1, and WP (5-40 g) and WPH (10 g) in 300 mL water were provided in experiment 2. At 30 min after consumption, the subjects were fed an ad libitum pizza meal (experiment 1) or a preset pizza meal (12 kcal/kg, experiment 2). Satiety, blood glucose, and insulin were measured at baseline and at intervals both before and after the meals. RESULTS In experiment 1, 20-40 g WP suppressed food intake (P < 0.0001) and 10-40 g WP reduced postmeal blood glucose concentrations and the area under the curve (AUC) (P < 0.05). In experiment 2, 10-40 g WP, but not WPH, reduced postmeal blood glucose AUC and insulin AUC in a dose-dependent manner (P < 0.05). The ratio of cumulative blood glucose to insulin AUCs (0-170 min) was reduced by > or =10 g WP but not by 10 g WPH. CONCLUSIONS WP consumed before a meal reduces food intake, postmeal blood glucose and insulin, and the ratio of cumulative blood glucose to insulin AUCs in a dose-dependent manner. Intact WP, but not WPH, contributes to blood glucose control by both insulin-dependent and insulin-independent mechanisms. This trial was registered at clinicaltrials.gov as NCT00988377 and NCT00988182.

Protein-sparing therapy in postoperative patients. Effects of added hypocaloric glucose or lipid.

In patients receiving hypocaloric total parenteral nutrition, protein sparing with infusions of amino acids alone is alleged to occur because low insulin levels allow mobilization of endogenous fat. Four groups of patients studied for their first four postoperative days received all their nutrition parenterally as: 150 g per day of glucose, protein (as amino acids, 1 g per kilogram per day) alone, protein plus 50 g per day of soybean-oil emulsion or protein plus 150 g per day of glucose. All groups of patients receiving protein had lesser negative nitrogen balance than patients receiving glucose alone. The addition of glucose to protein did not increase negative nitrogen balance. The protein-sparing effect of amino acids appears to be a function of the infused amino acids alone and is not related to the degree of endogenous fat mobilization.

Human milk feeding in premature infants: Protein,fat, and carbohydrate balances in the first two weeks of life

The nutritional adequacy of the premature infants own mothers milk was assessed during the first two weeks of life. Studies were carried out in three groups (n = 8) of infants of less than 1,300 gm birth weight, matched for gestational age and weight, and fed either pooled breast milk, their mothers own milk, or infant formula (SMA20 or SMA24). Macronutrient balances at the end of the first and second postnatal weeks demonstrated differences in nitrogen and lipid absorption and retention between groups. Nitrogen retentions (mg/kg/day) were similar to normal fetal accretion rates only in the PT and SMA24 groups. Fat absorption was poorest from the heat-sterilized PBM (average of 64.0% of intake) when compared to PT (88.2%) and SMA groups (83.3%). Average gross and metabolizable energy intakes were similar among groups. Nutritional status as measured by plasma total protein and albumin concentrations and weight gain tended to be poorest in the PBM-fed infants. It was concluded that either PT milk or infant formula of a composition similar to SMA24 are more appropriate than pooled banked milk for feeding the premature infant during the first two weeks of life.

Effect of television viewing at mealtime on food intake after a glucose preload in boys.

Television viewing (TVV) is considered a contributing factor to the development of childhood obesity yet it is unclear whether obesity results, in part, from increased energy intake during TVV. The objective of this study was to determine the effect of TVV on food intake (FI) of boys at a meal and its effect on caloric compensation at the test meal after a premeal glucose drink. On four separate mornings and in random order, boys received equally sweetened preloads containing Splenda sucralose or glucose [1.0 g/kg body weight (BW)] in 250 mL of water 2 h after a standard breakfast. Food intake from a pizza meal was measured 30 min later with or without TVV. Both preload treatment (p < 0.01) and TVV (p < 0.001) affected FI (kcal). TVV increased lunchtime FI by an average of 228 kcal. Glucose suppressed FI in the no TVV condition compared with control, but the effect was not statistically significant during TVV. Body composition and subjective appetite scores were positively associated with FI at the test lunch. In conclusion, TVV while eating a meal contributes to increased energy intake by delaying normal mealtime satiation and reducing satiety signals from previously consumed foods.

The Development of Cystathionase Activity During the First Year of Life

Summary: The development of hepatic cystathionase (EC 4.4.1.1) activity is dependent both upon the gestational age of the infant and the postnatal age. Full-term infants are born with greater hepatic cystathionase activity than pre-term infants, and the activity increases rapidly after birth reaching mature levels at about 3 months of age. Prematurely born infants have lower hepatic cystathionase activity at birth and like the full-term, the activity increases after birth. Cystathionase activity is not isolated to the liver. In both premature and full-term infants, it is present in the kidneys and adrenals, but of little significance in the pancreas. These in vitro measurements of cystathionase activity indicate that the premature infant is potentially capable of endogenous cysteine production if provided with adequate methionine.Speculation: We postulate that, if given adequate methionine, the preterm infant may have sufficient cystathionase capacity to produce cysteine in amounts adequate to meet estimated needs.

Aspartame: Effect on lunch-time food intake, appetite and hedonic response in children

Two experiments were conducted, each with 20 healthy 9-10-year-old children. After an overnight fast, subjects were given a standardized breakfast at 0830 hrs, the treatments at 1030 hrs, and a lunch containing an excess of foods at 1200 hrs. Visual analog scales of hunger, fullness, and desire to eat were administered 5 min before and 20 and 85 min after treatment. Lunch-time food intake was measured. In experiment 1, either aspartame (34 mg/kg), or the equivalent sweetness of sodium cyclamate, was given in an ice slurry (300 ml) of unsweetened strawberry Kool-Aid with carbohydrate (1.75 g/kg polycose). In experiment 2, drinks (300 ml) contained either sucrose (1.75 g/kg) or aspartame (9.7 mg/kg). In both experiments, significant meal- and time-dependent effects were observed for subjective feelings of hunger, fullness and desire to eat. Treatments, however, did not affect either subjective feelings of appetite or lunch-time food intake. Thus, aspartame consumed without or with carbohydrate, did not affect either hunger or food intake of children when compared with the sweeteners sodium cyclamate and sucrose, respectively.

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.

Snacking Definitions: Impact on Interpretation of the Literature and Dietary Recommendations

Snacking is a ubiquitous practice that has increased in recent years. However, the impact of snacking on the diet is difficult to assess because a variety of approaches have been used to define snacking (and snack foods) in the literature. This lack of a universally accepted definition complicates interpretation of the literature and limits the development of science-based recommendations for consumers. The purpose of this review is to illustrate this problem by showing that the conclusions derived from the literature are heavily dependent on the definition used or implied by the authors. It is suggested that the a universally accepted definition for snacking be developed by a coalition of stakeholders to provide a template for future research, guidance for the food industry and to enable the development of well-substantiated dietary recommendations.