Nutrition Midterm

HCI in the stomach

Aids in digestion by breaking down food, activating pepsin, and killing harmful bacteria.

Bicarbonate in the Small Intestine

Neutralizes stomach acid to prevent damage and create an optimal environment for enzyme activity.

Small Intestine

• Site of nutrient absorption.

• Lined with villi and microvilli to increase surface area for absorption.

Bile

• Made in the liver.

• Stored in the gallbladder.

• Emulsifies fats to aid in digestion and absorption.

Pancreas

• Digestion: Produces digestive enzymes.

• Blood glucose regulation: Secretes insulin and glucagon.

Large Intestine

Absorbs water and electrolytes; houses microbiome.

Microbiome

A collection of beneficial bacteria aiding digestion, immune function, and metabolism.

Carbohydrates

Stored as glycogen in the liver and muscles.

Lipids

Stored in adipose tissue.

Proteins

Not stored, but used in body tissues and muscle

GI Tract Diseases

• Common diseases: GERD, IBS, celiac disease, Crohn’s disease.

• Symptoms: Abdominal pain, bloating, diarrhea, constipation.

• Treatments: Dietary changes, medications, lifestyle adjustments.

Monosaccharides

Single sugar molecules (glucose, fructose, galactose).

Disaccharides

Two sugar molecules (sucrose, lactose, maltose).

Polysaccharides

Long chains of sugar molecules (starch, glycogen, fiber).

Simple vs. Complex Carbohydrates

Simple carbs digest quickly; complex carbs provide sustained energy.

Whole grains

Contain bran, germ, and endosperm

Refined grains

Processed to remove fiber and nutrients.

Functions of Carbohydrates

• Primary energy source.

• Helps in brain function and muscle activity.

Blood Sugar Regulation

Insulin (lowers blood sugar) and Glucagon (raises blood sugar) are produced in the pancreas.

Storage of Glucose

Liver and muscles store glycogen; the liver releases glucose into the bloodstream when needed.

Saturated vs. Unsaturated

Similarities:

• Both are types of fatty acids found in food.

• Both provide energy and are important for cell membrane structure.

• Both contain a carboxyl (-COOH) group at one end and a hydrocarbon chain.

Differences:

• Saturated fatty acids have no double bonds between carbon atoms; they are "saturated" with hydrogen atoms, making them solid at room temperature (e.g., butter, coconut oil).

• Unsaturated fatty acids contain one or more double bonds, creating kinks in the structure that make them liquid at room temperature (e.g., olive oil, fish oil).

Omega-3 vs. Omega-6

Similarities:

• Both are essential polyunsaturated fatty acids (PUFAs) needed for health.

• Both have multiple double bonds.

• Both play roles in inflammation, brain function, and heart health.

Differences:

• Omega-3 fatty acids (e.g., alpha-linolenic acid, EPA, DHA) have their first double bond at the third carbon from the methyl (CH₃) end. They reduce inflammation and support brain and heart health. Found in fish, flaxseeds, and walnuts.

• Omega-6 fatty acids (e.g., linoleic acid, arachidonic acid) have their first double bond at the sixth carbon from the methyl end. They can promote inflammation when consumed in excess. Found in vegetable oils, nuts, and seeds.

Linolenic (Omega-3) vs. Linoleic (Omega-6)

Similarities:

• Both are essential fatty acids that must be obtained from the diet.

• Both are polyunsaturated fatty acids (PUFAs).

• Both serve as precursors to other important fatty acids.

Differences:

• Linolenic acid (alpha-linolenic acid, ALA) is an omega-3 fatty acid with three double bonds. It is converted into EPA and DHA, supporting brain and heart health.

• Linoleic acid (LA) is an omega-6 fatty acid with two double bonds. It is converted into arachidonic acid, which plays a role in inflammation and immune response.

Cis vs. Trans Fatty Acids

Similarities:

• Both have at least one double bond.

• Both can be found naturally in food, but trans fats are often industrially produced.

• Both affect cholesterol levels and heart health.

Differences:

• Cis fatty acids have hydrogen atoms on the same side of the double bond, creating a bend in the molecule. They are found naturally in healthy fats like olive oil and fish oil.

• Trans fatty acids have hydrogen atoms on opposite sides of the double bond, making them more linear and solid at room temperature. Most trans fats are artificially made (e.g., partially hydrogenated oils) and increase the risk of heart disease.

Why cholesterol is not essential

• The body produces cholesterol primarily in the liver, generating about 800–1,200 mg per day, which is sufficient for physiological functions.

• Cholesterol is necessary for:

  • Cell membrane structure (maintains fluidity and integrity).

  • Hormone production (e.g., estrogen, testosterone, cortisol).

  • Bile acid synthesis (aids fat digestion).

  • Vitamin D synthesis (when skin is exposed to sunlight).

• Even if dietary cholesterol intake is low, the body compensates by increasing its production. Conversely, if intake is high, the liver adjusts by making less.

Food Sources of Cholesterol

Since cholesterol is only found in animal-based foods, some common sources include:

• Egg yolks (one of the richest sources).

• Red meat (beef, pork, lamb).

• Poultry (chicken, turkey, duck).

• Dairy products (butter, cheese, whole milk).

• Shellfish (shrimp, crab, lobster).

• Organ meats (liver, kidney, brain).

Functions of Lipids

Energy storage, insulation, hormone production.

Lipoproteins & Transport

LDL ("bad" cholesterol): Can lead to heart disease.

HDL ("good" cholesterol): Helps remove cholesterol from the bloodstream

Heart Disease Risk Factors

High LDL, low HDL, smoking, poor diet, sedentary lifestyle

Fat Intake Recommendations

Limit saturated and trans fats; prioritize healthy fats from plants and fish.

Amino Acids

• Essential (9): Must be obtained from food.

• Non-essential: Can be synthesized by the body.

Protein Functions

Building and repairing tissues, enzyme function, immune response.

Denaturation

Proteins lose structure due to heat, acid, or mechanical action.

Enzymes

Biological catalysts that speed up reactions in the body.

Protein Needs & Calculation

• RDA: 0.8 g/kg body weight.

• Example Calculation: A 60 kg person needs 48 g protein/day.

Protein Quality

• High-quality: Animal proteins, soy.

• Low-quality: Some plant proteins, require combining for complete amino acids.

Immune Function

Antibodies are proteins.

Food Allergies

Allergic reactions occur to specific proteins.

Vegetarian Diets

• Benefits: Lower risk of chronic disease.

• Risks: Possible nutrient deficiencies (B12, iron, omega-3s).

Basal Metabolic Rate (BMR)

Energy at rest (~60% of TEE).

Thermic Effect of Food (TEF)

Energy for digestion (~10% of TEE).

Physical Activity

Variable (~30% of TEE).

Factors Affecting Energy Expenditure

Age, muscle mass, activity level, hormones.

Measuring Body Composition

BMI is limited; alternatives include DEXA, skinfold measurements

Body Fat Distribution & Disease Risk

Visceral fat (around organs) increases disease risk.

Weight Loss Goals

1-2 lbs/week is a healthy target (based on 500-1000 kcal/day deficit).

Weight Bias & Social Pressures

Can lead to discrimination and psychological distress.

Eating Disorders

• Risk Groups: Adolescents, athletes, those under social pressure.

• Types & Symptoms:

  • Anorexia Nervosa: Extreme restriction, weight loss, amenorrhea.

  • Bulimia Nervosa: Bingeing and purging.

  • Binge Eating Disorder: Excessive eating without purging.

Health Consequences of Anorexia

Osteoporosis, slowed metabolism, heart complications.

Treatment Approaches for Eating Disorders

Therapy, nutrition counseling, medical intervention.