Essential Nutrition Principles and Human Physiology

Foundations of Health and Nutrition

Only two common lifestyle habits have a stronger influence on long-term health than dietary choices: smoking and other tobacco use, and excessive alcohol consumption.

The Six Classes of Nutrients

• Water
• Carbohydrates
• Fat
• Protein
• Vitamins
• Minerals

Essential Nutrients and Energy

An essential nutrient is required for normal body functioning and cannot be synthesized by the body; it must be obtained from a dietary source.

• Carbohydrates: 4 cal/g
• Protein: 4 cal/g
• Fat: 9 cal/g

Minerals are inorganic. Macronutrients that provide energy the body can use include carbohydrates, fat, protein, and alcohol.

Scientific Research and Dietary Guidelines

The scientific method involves observation, hypothesis, testing, and conclusion. Epidemiology studies factors contributing to health issues, such as cohort studies (collecting info over time) and Randomized Control Trials (RCTs).

Dietary guidelines apply to most people age 2 and older and are updated every 5 years.

Understanding Dietary Reference Intakes (DRI)

DRIs address energy and nutrient intake to prevent both excess and deficiencies. These recommendations are designed for healthy populations.

• EAR (Estimated Average Requirements): Used to evaluate population intake and make recommendations based on life stage and gender.
• AI (Adequate Intake): Recommended specific amounts for individuals.
• RDA (Recommended Dietary Allowance): Recommended specific amounts for individuals.
• UL (Tolerable Upper Intake Levels): Sets a ceiling to prevent nutrient toxicities.
• AMDR (Acceptable Macronutrient Distribution Ranges): Healthy ranges for energy-yielding nutrients (45-65% carbs, 20-35% fat, 10-35% protein).
• EER (Estimated Energy Requirement): Predicted energy needs for your specific body.

Physiology and Digestion

Cells organize into tissues, and tissues form organs. The hypothalamus and hormones control hunger (physical need) and appetite (psychological desire).

Key Hormones and Functions

• Gastrin: Secreted by the stomach; stimulates hydrochloric acid.
• Ghrelin: Secreted by the stomach; increases appetite.
• Secretin: Secreted from the duodenal mucosa.
• Cholecystokinin: Stimulates the gallbladder to expel bile.

The GI tract limits the absorption of toxins, while lymph fluid assists in immune function, fluid balance, and lipid absorption. Nerves release neurotransmitters, and the hypothalamus senses conditions in the blood to maintain homeostasis.