nutrition

Fundamentals of Nutrition and Food Choice Factors

• Definition of Nutrition: The scientific discipline connecting food intake to overall health, wellness, and disease outcomes.

• Organismal Processing of Food: Human nutrition encompasses the full biological sequence by which an organism ingests, digests, absorbs, transports, utilizes, and excretes food substances.

• Primary Functions of Nutrients: Provide energy (measured in kilocalories), supply vital building blocks for cellular growth and structural balance, and regulate physiological processes to maintain homeostasis.

• Essential Nutrients: Specific chemical compounds that cannot be synthesized by the body in sufficient quantities and must be acquired directly from the diet to sustain biological function.

• Protein as Structural Building Blocks: Dietary protein provides the requisite amino acid building blocks to synthesize functional proteins, build collagen, and initiate bone structure formation.

• Role of Iron in Gas Transport: Iron is a critical mineral component of hemoglobin that binds to oxygen for systemic transport.

• Determinants of Food Choices:

  • Sensory Attributes: Flavor, texture, and appearance represent the primary factors dictating individual food selection.

  • Environmental and Social Exposures: Early life influences that expose individuals to diverse people, places, and events exert a sustained impact on lifelong food choices.

Physiological vs. Psychological Drives to Eat

• Primary Food Drives:

  • Hunger: The primary physiological (internal) biological mechanism driving the body to seek and consume food.

  • Appetite: The psychological (external) drive triggered by environmental cues, sensory appealing features, or social settings prompting food seeking and intake.

Classification of Nutrients: Macronutrients and Micronutrients

• Macronutrients:

  • Required in gram ($\text{g}$) quantities within the daily diet.

  • Yield caloric energy to the body.

  • Major classes: Carbohydrates, Proteins, and Lipids/Fats.

• Micronutrients:

  • Required in milligram ($\text{mg}$) or microgram ($\mu\text{g}$) quantities within the daily diet.

  • Do not provide caloric energy.

  • Major classes: Vitamins and Minerals.

Carbohydrates

• Chemical Composition: Composed of Carbon ($\text{C}$), Hydrogen ($\text{H}$), and Oxygen ($\text{O}$).

• Energy Density: Yields approximately $4\,\text{kcal/g}$.

• Temperature Regulation: Does not directly regulate body temperature.

• Major Dietary Sources: Fruits, vegetables, grains, beans, and sugars.

• Structural Classification:

  • Monosaccharides: Single sugar molecules such as glucose (3 major monosaccharides).

  • Disaccharides: Double sugar units such as sucrose (3 major disaccharides).

  • Simple Sugars:

  • Table sugar (sucrose)

  • Blood sugar (glucose)

  • Complex Carbohydrates:

  • Starch (found in grains)

  • Glycogen (animal storage carbohydrate)

  • Fiber (indigestible plant polysaccharide)

Lipids (Fats and Oils)

• Chemical Composition: Composed of Carbon ($\text{C}$), Hydrogen ($\text{H}$), and Oxygen ($\text{O}$).

• Energy Density: Yields approximately $9\,\text{kcal/g}$.

• Solubility: Hydrophobic substances that do NOT dissolve in water.

• Source Classifications and Health Implications:

  • Animal Fats: Solid at room temperature. Intake should be limited because saturated animal fats raise blood cholesterol levels, contributing to cardiovascular disease.

  • Plant Oils: Liquid at room temperature. Serve as important sources of essential fatty acids.

• Molecular Structure:

  • Triglyceride: The primary storage and dietary form of lipid, composed of a glycerol molecule bound to three fatty acid chains made of carbon, oxygen, and hydrogen atoms.

Proteins

• Chemical Composition: Composed of Carbon ($\text{C}$), Oxygen ($\text{O}$), Hydrogen ($\text{H}$), AND Nitrogen ($\text{N}$).

• Primary Structure: Formed when individual amino acids are joined together by peptide bonds.

• Biological Functions:

  • Serves as the main structural material in the human body.

  • Forms a major constituent of bone and muscle tissue.

  • Essential functional component of blood, cell membranes, enzymes, hormones, and immune factors.

  • Specific example: Hemoglobin, a specialized protein found in red blood cells that transports oxygen throughout the circulatory system.

• Energy Density: Yields approximately $4\,\text{kcal/g}$.

• Dietary Sources: Obtained from both plant and animal food sources.

Vitamins

• Chemical Composition: Organic compounds composed of Carbon ($\text{C}$), Hydrogen ($\text{H}$), Oxygen ($\text{O}$), Nitrogen ($\text{N}$), Phosphorus ($\text{P}$), Sulfur ($\text{S}$), and other elements.

• Energy Yield: Contains no useable caloric energy ($0\,\text{kcal/g}$).

• Physiological Function: Enable and catalyze biochemical reactions to occur throughout the body.

• Solubilities:

  • Fat-Soluble Vitamins: Vitamin A, Vitamin D, Vitamin E, and Vitamin K.

  • Water-Soluble Vitamins: B-complex vitamins and Vitamin C.

• Stability: Heat from cooking destroys water-soluble vitamins far more readily than fat-soluble vitamins.

Minerals

• Chemical Structure: Stand-alone elements and inorganic substances that DO NOT contain carbon atoms ($\text{C}$).

• Heat Stability: Chemically stable; not destroyed during cooking or thermal processing.

• Classification: Categorized as major minerals or trace minerals depending on daily requirements.

• Physiological Functions: Perform crucial electrolyte functions and fluid balance regulation; supply no caloric energy ($0\,\text{kcal/g}$).

Water

• Chemical Composition: Inorganic compound composed of Hydrogen ($\text{H}$) and Oxygen ($\text{O}$) ($\text{H}_2\text{O}$).

• Body Composition Contribution: Represents the majority of human body weight ($50\%\text{ to }70\%$).

• Physiological Functions:

  • Serves as a universal biological solvent and physical lubricant.

  • Transports nutrients to cells and excretes waste products from the body.

  • Acts as the main medium for core body temperature regulation.

• Daily Intake Requirements: Recommended daily fluid intake ranges from $9\text{ to }13\,\text{cups/day}$.

• Energy Yield: Delivers no caloric energy ($0\,\text{kcal/g}$).

Functional Classifications of Nutrients

• Category 1: Nutrients that Provide Energy:

  • Most carbohydrates

  • Proteins

  • Most lipids

• Category 2: Nutrients that Promote Growth, Development, and Maintenance:

  • Proteins

  • Some lipids

  • Some vitamins

  • Some minerals

• Category 3: Nutrients that Regulate Body Processes (Homeostasis):

  • Proteins (specifically acting as enzymes and hormones)

  • Some lipids

  • Some vitamins

  • Some minerals

  • Water

Phytochemicals, Zoochemicals, and Functional Foods

• Phytochemicals:

  • Health-promoting non-nutrient active chemicals found in plants, particularly in fruits and vegetables.

  • Health Benefits: Can inhibit the initiation and proliferation of cancer cells.

  • Mode of Consumption: Health benefits are best obtained through the consumption of whole foods rather than dietary supplements.

  • Practical Dietary Strategies to Boost Phytochemicals:

  • Include vegetables as side dishes.

  • Prepare quick grain side dishes containing whole grains and vegetables.

  • Choose fruit-filled cookies or baked goods.

  • Eat fresh fruit or trail mix for snacks.

  • Add extra fresh vegetables to sandwiches.

• Zoochemicals:

  • Non-essential bioactive components found in animal products that convey health benefits.

  • Examples: Fatty fish (providing omega-3 fatty acids) and fermented dairy products (providing probiotics).

• Functional Foods:

  • Foods that provide health benefits beyond those supplied by traditional nutrient contents.

  • Categories and Examples:

  • Conventional whole foods: Unprocessed fruits, vegetables, and dairy products.

  • Modified / Fortified foods: Enriched foods, such as orange juice fortified with added vitamins and minerals.

Metric System and Quantitative Conversions in Nutrition

• Length Units (Meter):

  • $1\,\text{centimeter} = \frac{1}{100}\,\text{meter}$

  • $2.54\,\text{centimeters} = 1\,\text{inch}$

• Weight Units (Gram and Kilogram):

  • $1\,\text{gram (g)} \approx \frac{1}{30}\,\text{ounce}$

  • $28\,\text{grams} = 1\,\text{ounce}$

  • $5\,\text{grams of sugar} \approx 1\,\text{teaspoon}$

  • $1\,\text{kilogram (kg)} = 1000\,\text{grams}$

  • $1\,\text{kg} \approx 2.2\,\text{pounds}$

  • Conversion Formula: Convert body weight in pounds ($\text{lb}$) to kilograms ($\text{kg}$) by dividing by $2.2$:

$\text{Weight in kg} = \frac{\text{Weight in lb}}{2.2}$

• Volume Units (Liter):

  • $1\,\text{liter (L)} = 1000\,\text{milliliters (mL)}$

  • $1\,\text{teaspoon} = 5\,\text{mL}$

  • $1\,\text{cup} = 240\,\text{mL}$

  • $1\,\text{quart (4 cups)} \approx 1\,\text{L}$ ($0.946\,\text{liters}$ to be exact).

Energy Values and Caloric Calculations

• Caloric Yield by Substrate:

  • Carbohydrates: $4\,\text{kcal/g}$

  • Proteins: $4\,\text{kcal/g}$

  • Fats (Lipids): $9\,\text{kcal/g}$

  • Alcohol: $7\,\text{kcal/g}$ (supplies energy but is not considered an essential nutrient)

• Definitions of Caloric Units:

  • calorie (lowercase c, small calorie): The amount of heat energy required to raise the temperature of $1\,\text{gram}$ of water by $1^\circ\text{C}$.

  • Kilocalorie (kcal) / Calorie (Capital C, Food Calorie):

$1000\,\text{calories} = 1\,\text{kilocalorie} = 1\,\text{food Calorie}$

• Kilocalorie Definition: The amount of heat energy required to raise the temperature of $1\,\text{kilogram}$ ($1\,\text{liter}$) of water by $1^\circ\text{C}$.

• Food Label Standards: Energy values printed on consumer food labels are expressed in Calories (Capital C).

  • Caloric Calculation Example ("Chicken Sandwich Meal"):

• Meal Composition:

  • Carbohydrates: $46\,\text{g}$

  • Protein: $45\,\text{g}$

  • Fat: $14\,\text{g}$

  • Alcohol: $0\,\text{g}$

• Calculation Steps:

  • Energy from Carbohydrate: $46\,\text{g} \times 4\,\text{kcal/g} = 184\,\text{kcal}$

  • Energy from Protein: $45\,\text{g} \times 4\,\text{kcal/g} = 180\,\text{kcal}$

  • Energy from Fat: $14\,\text{g} \times 9\,\text{kcal/g} = 126\,\text{kcal}$

  • Energy from Alcohol: $0\,\text{g} \times 7\,\text{kcal/g} = 0\,\text{kcal}$

  • Total Meal Caloric Value:

$184\,\text{kcal} + 180\,\text{kcal} + 126\,\text{kcal} + 0\,\text{kcal} = 490\,\text{kcal}$

Scientific Method and Research Methodology

• Sequential Steps of the Scientific Method:

  1. Observation: Identifying a biological trend or disease phenomenon.

  2. Hypothesis: Formulating an explanation to test.

  3. Literature Review / Research: Reviewing existing scientific publications.

  4. Research Experiments: Conducting empirical testing.

  5. Peer Review: Critical evaluation of experimental design and processes by independent scientific experts.

  6. Follow-up Experiments: Replicating trials to confirm reproducibility.

  7. Hypothesis Decision: Formally accepting or rejecting the hypothesis based on collected evidence.

• Health, Lifestyle, and Chronic Disease Risk:

  • Lifestyle choices represent the primary factor in maintaining optimal health.

  • A poor diet and a sedentary lifestyle are primary modifiable risk factors for chronic diseases.

  • Example - Pathophysiology of Atherosclerosis / Heart Attack: Atherosclerotic plaque attaches along inner arterial walls, reducing arterial diameter and obstructing blood flow.

Experimental Study Designs in Human Nutrition

• Ethical Approvals: All human experimental research requires oversight and approval from an Institutional Review Board (IRB) to safeguard human subjects.

• Epidemiological Study Types (Observational):

  • Population Differences: Comparing lifestyle and disease rates across geographical or cultural populations (e.g., studying health outcomes of the Mediterranean Lifestyle).

  • Cohort Studies: Tracking a defined population group over an extended time period to observe long-term health outcomes (e.g., the Framingham Heart Study).

  • Case-Control Studies: Retrospectively comparing individuals with a specific condition ("cases") against matched individuals without the condition ("controls").

• Human Clinical Experiments:

  • Intervention studies designed to test a specific variable in a controlled setting, comparing a Treatment Group against a Control / Placebo Group.

Systematic Reviews, Scientific Integrity, and Public Health Objectives

• Systematic Reviews: Critical evaluation and structured synthesis of multiple primary research studies to generate comprehensive evidence-based conclusions.

• Scientific Integrity: Demonstrated by strict adherence to professional values, objectivity, and ethical protocols during research design, execution, interpretation, and reporting.

• National Dietary Surveillance and Public Health Targets:

  • National Health and Nutrition Examination Survey (NHANES): Population intake surveys report average macronutrient distribution as approximately $50\%$ carbohydrates, $33\%$ fat, and $16\%$ protein.

  • Healthy People National Objectives:

  • Target 1: Reduce the prevalence of iron deficiency among young children aged $1\text{ to }2\,\text{years}$.

  • Target 2: Increase the proportion of schools that do not sell less healthy food and beverage items.