Metal Activated Enzymes versus Metalloenzymes

Enzymes that depend on metal ions as cofactors fall into two categories metal-activated enzymes and metalloenzymes. As the name implies, metal-activated enzymes are prompted to greater catalytic activity by the presence of a mono- or divalent metal ion exterior to the protein (in the assay medium). The metal may activate the substrate (e.g., Mg2+ with ATP), engage the enzyme directly, or enter into equilibrium with the enzyme exploiting its ionic charge to render a more favorable substrate...

Examples of Food Fortification Programs in Developing Countries

Despite the multiple limitations that affect food fortification in the developing world, there are several examples that confirm its feasibility and benefits. Vegetable Fats and Oil Fortified with Vitamin A and D Addition of vitamin A to margarine and other vegetable fats started in 1918 in Denmark, when cases of xerophthalmia were associated with the replacement of butter by margarine. Then, the practice of nutritional equivalence, that is emulating the nutritional composition of butter, was...

Total Energy Expenditure and its Components

It is customary to consider energy expenditure as being made up of three components the energy spent for basal metabolism (or basal metabolic rate), the energy spent on physical activity, and the increase in resting energy expenditure in response to a variety of stimuli (in particular food, cold, stress, and drugs). These three components are depicted in Figure 4. Basal Metabolic Rate (BMR) or Resting Metabolic Rate (RMR) This is the largest component of energy expenditure accounting for...

Metabolism of Dietary Nucleic Acids in Humans

Hman Nutrion Images

The normal human diet is rich in both DNA and RNA since food is derived from once-living organisms. The metabolism of these exogenous nucleic acids follows a similar pattern to the intra-cellular process described previously, but the bacterial flora of the intestine are the first point of attack. This digestion is rapid. Studies in pigs (confirmed by later studies in humans) demonstrated that up to 50 of radiolabeled dietary purine was degraded and lost as carbon dioxide gas within 30 min, with...

Static Biochemical Tests

Static tests measure chemically the content of nutrients, their active or inactive metabolites, or other related components in tissues and urine. The choice of tissue or fluid depends on the information required short-term or long-term status, body pool or tissue store and on the condition of the subject. Various confounding factors affect static biochemical tests. Some are of a general kind, such as age, sex, ethnic group, physiological and hormonal status, seasonality, elevation, and thus...

Methods for Estimating Dietary Intake at the Household Level Household Budget Surveys

Techniques for estimating intake at the household level include the food account method, the inventory method, the household record, and the list recall method. These methods measure all foods and beverages available for consumption by a household or family group during a specified time period of between 1 and 4 weeks, although some last for 23 months. Wastage factors are sometimes applied. Household surveys provide data for per capita consumption of foods or nutrients, not intake for specific...

Anthropometric Measurements Height

Skinfold Areas

Height, or stature, is measured in adults and children over the age of 2 years using a stadiometer, a portable anthropometer, or a moveable headboard on a vertical measuring rod. The measuring device should be checked for accuracy using a standard 2-m steel tape. Subjects should be measured to the nearest 0.1 cm. Subjects, in minimal clothing with bare heads and feet, should stand straight, arms hanging loosely to the side, feet together and with heels, buttocks and shoulder blades in contact...

Severe Malnutrition and Reductive Adaptation

The acute phase response to an infection is muted in severe protein-energy malnutrition in part of a process referred to as 'reductive adaptation,' whereby the structure and function of cells or tissues cannot be maintained due to the limited supply of energy resulting from decreased nutritional intake. Protein synthesis from amino acids is highly energy-dependent and proteins have a wide variety of structural and functional roles in the body, including the cytokines that initiate the acute...

Pathophysiology of Uncontrolled Diabetes

Hyperosmotic Dehydration Symptoms

Uncontrolled diabetes mellitus occurs when circulating insulin levels are inadequate to lower elevated blood glucose concentrations. This condition includes a spectrum of metabolic abnormalities that range from the effects of mild insulin deficiency (i.e., hyperglycemia) to the effects of marked and prolonged insulinopenia (i.e., ketoacidosis and fluid and electrolyte depletion). Diabetic ketoacidosis, which is the most severe acute manifestation of insulin deficiency, is almost entirely...

Principles of Dietary Management of Diabetes

Assessment The first step for planning an appropriate nutrition plan is a full assessment of the diabetic patient. Topics covered in the nutritional assessment are included in Table 1. Individualization Individualization is a cardinal principle of medical nutrition therapy for diabetes, facilitating individual lifestyle and behavior changes that will lead to improved metabolic control. Since no one diet fits all, the standard, printed diabetic diet is inadequate. Rather, people with diabetes...

Nucleosides and Nucleotides in the Diet

In healthy adults, the normal diet is a good source of nucleic acids, nucleotides, and nucleosides, and no supplementation is necessary. Pharmacological uses for nucleosides and nucleotides Oral uridine, as described earlier, can be used where de novo biosynthesis of pyrimidines is defective, and it may be useful in reversing some effects of mitochondrial dysfunction and to minimize the toxic effect of the antitumor drug 5-fluorouracil. Uridine is also a precursor for UDP-glucose, essential for...

Classification of Hyperlipidemia

There are a number of classification systems available. In 1967, Fredrickson, Levy, and Lees introduced the first classification as a method of reporting that lipoproteins were raised. The World Health Organization adopted this classification (Table 3). In 1987, the European Atherosclerosis Society recommended a five-group classification of primary hyperlipidemia (Table 4), and the National Cholesterol Education Program Adult Treatment Panel III published guidelines in 2002 for normal and...

Diseases of Carbohydrate Metabolism

Fructose intolerance and essential fructosuria Fruc-Fructose intolerance and essential fructosuria are genetic defects of fructose metabolism. Fructose intolerance is an autosomal recessive disease, caused by a genetic defect in fructose 1-phosphate aldolase (aldolase B) in the liver. The symptoms of aldolase B deficiency occur when the infant is exposed to fructose. Aldolase B deficiency results in phosphate depletion and fructose 1-phosphate accumulation in the liver. Consequently,...

Abnormalities of Hormones and Other Circulating Factors

Growth hormone Obesity is typically accompanied by a decrease in growth hormone (GH) levels and an increase in growth hormone binding protein levels. An inverse relation exists between GH levels and percentage fat mass. GH levels fall with increasing age. GH is released by the anterior pituitary and affects lipid, carbohydrate, and protein metabolism. GH also controls the rate of skeletal and visceral growth. GH is lipolytic in adipose tissue. Animal studies show enhanced catecholamine-induced...

Neuroglycopenic Syndromes

Four more or less distinct neuroglycopenic syndromes (one of which is so rare that it will not be considered further here) can be recognized. They are not mutually exclusive, nor do they depend upon the ultimate cause of the hypoglycemia. This syndrome comprises a collection of vague symptoms such as feelings of alternating hot and cold, feeling unwell, anxiety, panic, inner trembling, unnatural feelings, blurring of vision, and palpitations, any or all of which may be accompanied by objective...

Nucleic Acid Content of Foods

The nucleic acid content of different foods is expressed generally in terms of purine equivalents, with the data derived from the hydrolysis of nucleic acids and free nucleotides to the constituent bases. Careful analysis by Robert McCance, Elsie Widdow-son, and colleagues since the 1930s forms the basis of tables of the composition of foodstuffs. Foods may be classified into three groups high, low, or essentially purine free (Table 1). As a general rule, growing organisms such as yeast, or...