Nutrition and Metabolism Quiz

Human Nutrition & Biochemical Parameters of Nutrition

• The science of nutrition focuses on the qualitative and quantitative aspects of diet and the utilization of dietary components for maintaining health.
• Major components for human nutrition include carbohydrates, proteins, lipids, minerals, trace elements, vitamins, and fiber. These are biochemically well-defined components.
• Essential nutrients are those that the body cannot synthesize and must be obtained through diet, including essential amino acids and fatty acids, and specific vitamins (A, E, K, water-soluble vitamins). Vitamin D is essential for children, but not adults.

Essential Amino Acids

• A list of essential and conditionally essential amino acids is included.
• The table differentiates between nonessential, conditionally essential, and essential amino acids.

Essential Fatty Acids

• Alpha-linolenic acid (ALA) and linoleic acid (LA) are essential fatty acids.

Energy Requirements

• Energy intake should balance energy expenditure based on age, sex, reproductive status, disease, injury and therapeutic interventions, body size and composition.
• Energy requirements (ER) for children and pregnant/lactating women include energy for tissue development and milk production.
• Energy balance is when energy intake equals energy expenditure and changes in stored energy.

Basal Metabolic Rate (BMR)

• BMR is the resting energy expenditure, about 60-70% of total calories burned.
• BMR encompasses the energy used for basic bodily functions, including heart beat, cell proliferation, respiration, maintaining body temperature, circulation and nutrient processing.
• BMR is affected by factors like age, weight, height, gender, environmental temperature, dieting, and exercise habits.
• BMR can be measured via direct or indirect calorimetry.

Nitrogen Balance

• Nitrogen balance assesses expenditure of endogenous energy.
• A positive nitrogen balance (protein intake > protein loss) is crucial for growth (children and fetus), pregnancy, lactation and physiologically stressful situations.
• Accurate assessment of nitrogen output needs a detailed diet record and measurement of fecal and urinary nitrogen (with correction factors).
• Urine urea nitrogen (UUN) is used to estimate total urinary nitrogen (TUN). UUN constitutes 80-90% of the total nitrogen output.

Excessive Nutrients

• Excessive nutrients are stored as fat and can lead to obesity.
• If insufficient nutrients are available, stored fats and muscle proteins are used for energy (i.e. glucose).

Starvation

• Starvation is a severe deficiency in caloric energy intake.
• Prolonged starvation can cause permanent organ damage and death.
• Starvation results from imbalance between energy intake and energy expenditure.

Starvation vs. Hypermetabolic Status

• Starvation is due to extreme lack of nutrients.
• Hypermetabolic status is an extreme metabolic response to injury or infection initiated by hormones and cytokines.
• During starvation, fat and muscle are used for energy, while in hypermetabolic states muscle protein is the primary source of amino acids for gluconeogenesis.

Observations of Hypermetabolic States

• Characteristics like fever and increased basal metabolic rate, nutritional needs, heart rate and cardiac output, negative nitrogen balance, increased hepatic gluconeogenesis, and synthesis of acute-phase proteins are associated.

Carbohydrates

• Carbohydrates are the primary energy source, contributing 50-60% of total calories.
• Excessive carbohydrate intake leads to weight gain.
• Insufficient intake leads to mobilization of body fat and associated ketosis, electrolyte loss, and dehydration.

Protein Requirements

• Dietary proteins provide amino acids for tissue protein synthesis.
• Essential amino acids are not synthesized by the body and must be obtained in the diet.
• The quality of dietary protein is determined by its essential amino acid content. Different life stages (infants, children, and adults) have different recommended essential amino acid proportions.

Good-Quality Protein

• Good-quality protein is essential to replace losses during hypermetabolic states associated with specific conditions like fever, burns, fractures, surgical trauma.

Nitrogen Balance Studies

• Nitrogen balance studies assess utilization of dietary amino acids for protein synthesis, and determine balance between anabolic/catabolic processes.
• For accurate assessment, detailed diet records and measurement of fecal and urinary nitrogen (with corrective factors) are needed.

Urinary Urea Nitrogen

• Urinary urea nitrogen (UUN) estimates total urinary nitrogen content.
• UUN is often used for estimating total nitrogen as it constitutes 80 to 90% of the total nitrogen output.

Positive vs. Negative Nitrogen Balance

• Positive nitrogen balance (protein intake > protein loss) is associated with health and required during growth, development, and pregnancy.
• Negative nitrogen balance (protein intake < protein loss) during starvation, and certain disease states requires corrective nutritional support.

Lipids

• Lipids are the most energy-dense macronutrients, providing 9 kcal per gram.
• A typical American diet contains 35-45% of calories from fat.
• The American Heart Association recommends reducing fat consumption to less than 30% of total caloric intake to maintain good health.

Minerals

• A list of electrolytes, minerals, and trace minerals is included here.

Fiber

• Fiber is composed of plant cell components indigestible by gut enzymes, but they greatly contribute to colonic health.
• Specific insoluble fibers like cellulose and lignin are good for colonic function.
• High fiber diets and fiber components (phytates) can decrease the bioavailability/absorption of minerals (like calcium, iron, and zinc).

Malnutrition

• Malnutrition refers to deficiencies or excesses in nutrient intake, nutritional imbalance or impaired nutrient utilization.
• It includes undernutrition (wasting, stunting, underweight, micronutrient deficiencies), overweight, obesity and diet-related non-communicable diseases.
• Wasting is defined as low weight-for-height, often associated with recent weight loss.

Types of Malnutrition

• Protein-energy malnutrition (PEM): is due to lack of sufficient protein and energy (calories).
• Micronutrient deficiency: Caused by lack of specific vitamins and minerals.
• Obesity: results from excessively consuming foods exceeding body needs.

Protein Malnutrition (Kwashiorkor)

• Kwashiorkor is a severe protein deficiency.
• It's prevalent in underdeveloped regions where breastfeeding infants are abruptly switched to high-carbohydrate diets.
• Predominantly affects children younger than 5 years old.

Protein-Energy Malnutrition (Marasmus)

• Marasmus is a severe overall nutritional deficiency in both calories and protein.
• Signs of starvation, such as loss of subcutaneous fat and muscle mass, are characteristic.

Degrees of Protein-Energy Malnutrition

• Protein-energy malnutrition degrees are classified based on Body Mass Index (BMI).

Undernutrition

• Undernutrition occurs when individuals receive insufficient nutrients to meet their needs.
• In developing countries, undernutrition is a major contributor to child mortality.

Micronutrient Deficiency

• Micronutrient deficiencies arise from lacking one or more vitamins and/or minerals.
• This can cause various health problems, including blindness, impaired immune function, increased infection severity, and decreased physical growth, intellectual potential and adult productivity.

Obesity

• Obesity is characterized by a Body Mass Index (BMI) of 30 or greater.
• Despite undernutrition remaining a major concern in developing countries, obesity is a growing problem across affluent societies globally.

BMI

• BMI is a measure of a person's nutritional status.
• Weight in kilograms is divided by the square of the person's height in meters (kg/m²).

Therapeutic Nutrition Support

• PEM and undernourishment, and specific nutrient deficiencies necessitate appropriate nutritional intervention for treatment.

Enteral Feeding

• Enteral feeding delivers nutrients directly into the stomach or intestine.
• Commercial formulas tailored to specific needs are used for maintaining proper nutrition.
• This method is generally preferred over total parenteral nutrition (TPN) when the gut is functional.

Parenteral Nutrition

• Parenteral nutrition (PN) provides nutrients intravenously.
• This approach is for patients unable to obtain necessary nutrients through normal oral or enteral routes.
• Isotopic lipid emulsions, glucose, amino acids, electrolytes, and micronutrients are included in these solutions, often offering up to 2500 kcal in 3 liters.

Biochemical Parameters for Monitoring Nutritional Status

• Assessing nutritional status of hospitalized patients (e.g., in hospitals or nursing homes) involves anthropometric measurements, physical examinations, and laboratory measurements (like those listed below).

Laboratory Tests for Monitoring PEM Response

• A table provides various laboratory parameters, explaining their associated rationals and comments, like urine urea nitrogen, Total urine nitrogen, Plasma albumin, Plasma transthyretin (prealbumin), Plasma transferrin, Plasma retinol-binding protein, Plasma zinc, and Plasma triglycerides.

Interpretation of Protein Synthesis Results

• Factors such as alteration in fluid volume and fluid shifts, presence of acute-phase response (like due to trauma, infection, or malignancy), etc., which affect albumin/protein values should be considered.
• Lower levels of certain proteins including transthyretin, transferrin, and retinol-binding proteins, despite being useful for following response to treatments, should not be exclusively attributed to malnutrition.
• Biological half-lives of specific proteins play a key role when monitoring responses to supplementation/treatment.