Principles of Nutrition: Ingestion, Digestion, Absorption, and Metabolism

This flashcard set covers the fundamental principles of nutrition including the stages of nutrient processing, metabolic rates, nitrogen balance, and clinical factors affecting metabolism.

Ingestion

The process of consuming food by the mouth and moving it through the digestive system.

Digestion

A systemic process that includes the breakdown and absorption of nutrients.

Absorption

The process occurring as components of nutrients pass through the digestive system into the bloodstream and lymphatic system.

Metabolism

The sum of all chemical processes that occur on a cellular level to maintain homeostasis.

Catabolism

The breaking down of substances with the resultant release of energy.

Anabolism

The use of energy to build or repair substances.

Metabolic storage of glucose

Glucose is converted to glycogen and stored in the liver and muscle tissue; surplus is converted to fat.

Metabolic storage of glycerol and fatty acids

Reassembled into triglycerides and stored in adipose tissue.

Basal metabolic rate (BMR)

Also called basal energy expenditure (BEE); the energy used in $24\,hr$ for involuntary activities determined while at rest and following a $12\text{-hr}$ fast.

Resting metabolic rate (RMR)

Also called resting energy expenditure (REE); calories needed for involuntary activities at rest without the requirement of a $12\text{-hr}$ fast.

Acute stress (metabolic effect)

Causes an increase in metabolism, blood glucose levels, and protein catabolism, where protein is broken down at a very rapid rate.

Protein requirements during stress

Can be increased to more than $2\,g/kg$ of body weight, or up to $25\%$ of total calories.

Factors that increase BMR

Lean, muscular body build; exposure to extreme temperatures; prolonged stress; rapid growth periods (infancy, puberty); pregnancy and lactation; physical conditioning.

Factors that decrease BMR

Short, overweight body build; starvation/malnutrition; age-related loss of lean body masses.

Conditions that increase metabolism

Fever, involuntary muscle tremors, hyperthyroidism, cancer, cardiac failure, burns, surgery/wound healing, and HIV/AIDS.

Drug-induced BMR increase

Medications such as Epinephrine, Levothyroxine, and Ephedrine sulfate.

Drug-induced BMR decrease

Medications such as Opioids, Muscle relaxants, and Barbiturates.

Nitrogen balance

The difference between the daily intake and excretion of nitrogen; an indicator of tissue integrity.

Positive nitrogen balance

Intake of nitrogen exceeds excretion, indicating the body is building more tissue than it breaks down; occurs during infancy, childhood, adolescence, pregnancy, and lactation.

Negative nitrogen balance

Excretion of nitrogen exceeds intake, indicating the body is breaking down more tissue than it is building; seen during illness, trauma, aging, and malnutrition.

Clinical findings of malnutrition

Pitting edema, hair loss, and wasted appearance.

Double-strength milk

A strategy to increase protein and caloric content by adding skim milk powder to milk.