Nutrition and Digestion Overview

Study Notes

A systematic process used to evaluate an individual's nutritional status.
Involves collecting and analyzing data to identify potential nutritional deficiencies or excesses.
Used to develop a personalized plan that addresses any identified nutritional needs.

Begins with mechanical digestion in the mouth (chewing) and continues in the stomach (churning) and intestines.
Chemical digestion involves breaking down food into smaller molecules by enzymes.
Enzymes include salivary amylase (mouth), pepsin (stomach), and pancreatic enzymes (intestines).

Salivary glands secrete saliva, containing amylase for carbohydrate breakdown.
The stomach secretes hydrochloric acid (HCl) and pepsinogen (activated to pepsin).
The pancreas secretes enzymes (amylase, lipase, proteases) into the small intestine and bicarbonate to neutralize stomach acid.
The liver and gallbladder secrete bile, stored in the gallbladder, which emulsifies fats.
The small intestine secretes enzymes (maltase, sucrase, lactase) to finalize digestion.

The small intestine is the primary site for nutrient absorption through villi and microvilli.
Carbohydrates are absorbed as monosaccharides.
Proteins are absorbed as amino acids.
Fats are absorbed as fatty acids and glycerol via lacteals (lymphatic system).
The large intestine absorbs water and electrolytes and forms and stores feces.

Basal Energy Expenditure (BEE)
- Minimum amount of energy expended compatible with life.
- Reflects energy used during 24 hours while at rest in a thermoneutral environment.
- Measurements should be done before any physical activity.
- Remains remarkably constant daily.
Thermic Effect of Food (TEF)
- Increase in energy expenditure associated with the consumption, digestion, and absorption of food.
Activity Thermogenesis (AT)
- The most variable component of TEE.

Also known as BMR (Basal Metabolic Rate).
Less strict than BEE, Resting Energy Expenditure (REE) or Resting Metabolic Rate (RMR).
- Energy expended in activities necessary to sustain normal body functions and homeostasis.
- Includes energy required by the central nervous system and for maintaining body temperature.
- Higher than BEE by 10-20%.

Age - Highest during periods of rapid growth, such as the first two years of life.
Body Composition - Primary predictor of REE, with lean body mass (LBM) being a key factor.
Climate - 5-20% higher in tropical countries.
Gender - 5% lower in women.
Hormonal Status - Endocrine disorders and during pregnancy can affect REE.
Temperature - Fever increases REE.

Obligatory thermogenesis - Energy required to digest, absorb, and metabolize nutrients, including the synthesis and storage of protein, fat, and carbohydrate.
Adaptive or facultative thermogenesis - “Excess” energy expended in addition to the obligatory thermogenesis. Thought to be attributable to metabolic inefficiency.

Activity thermogenesis (AT) - Physical activity is the most variable component of TEE.
Non-Exercise Activity Thermogenesis (NEAT) - Energy expended during the workday and during leisure-type activities (e.g., shopping, fidgeting, even gum chewing).

Sets health claims allowed to help consumers choose healthful foods and avoid misleading advertisements.
Determines serving sizes and standardizes descriptive terms.
Low Calorie – 40 calories or less per serving.
Calorie free - Less than 5 calories per serving.