Nutrition Lecture Notes

Nutrients and Their Functions

• A nutrient provides energy.

• Types of Nutrients:

  • Organic: Carbohydrates, Lipids, Proteins, Vitamins

  • Inorganic: Water, Minerals

• Macronutrients: Needed in large quantities (g-kg).

  • Carbohydrates

  • Lipids

  • Proteins

  • Water

• Micronutrients: Needed in small quantities ($\mu$$$\mu$$g-mg).

  • Vitamins

  • Minerals

• Organic: Carbon-based molecule.

• Inorganic: Non-carbon-based molecule.

• Essential Nutrients: Cannot be produced by the body, must be consumed.

• Non-Essential Nutrients: Can be produced by the body, don’t need to be consumed.

Energy from Nutrients

• Nutrients function as a source of energy.

• Energy in a nutrient is measured as a calorie.

  • 1 calorie = energy to raise the temperature of 1 mL of water by 1°C.

  • 1 Calorie = 1000 calories = 1 kcal.

• Calories per gram:

  • Carbohydrates: 4

  • Protein: 4

  • Lipids: 9

  • Alcohol: 7 (Not a nutrient, but has caloric value)

Nutrients as Building Blocks

• Nutrients provide building blocks for body structures.

• Lipids, carbohydrates, and proteins are important for cellular processes.

• Calcium and proteins from milk build bone, hair, teeth, and muscle.

• Vitamin D enhances calcium absorption.

• Vitamin D deficiency can lead to rickets.

• Vitamin A is required for light receptors in the retina.

Nutrients Regulate Body Processes

• B vitamins are involved in chemical reactions to produce ATP.

• Vitamin B12 is needed to produce red blood cells.

• Water helps maintain blood volume.

• Proteins, carbohydrates, and lipids function as hormones (cellular communication).

• Proteins also function as enzymes for cellular reactions.

Carbohydrates: Monosaccharides

• Monosaccharides = simple carbohydrates

• Examples: Glucose, Fructose, Galactose

Carbohydrates: Disaccharides

• Disaccharides = simple carbohydrates

• Sucrose: glucose + fructose

• Lactose: galactose + glucose

• Maltose: glucose + glucose

Focus on Disease: Lactose Intolerance

• Inability to break down lactose, the primary sugar in milk.

• Cause: Low lactase enzyme expression in the small intestine.

• Symptoms: Cramping, diarrhea due to lactose breakdown in the large intestine.

• Treatment: Synthetic lactase (Lactaid).

Carbohydrates: Polysaccharides

• Polysaccharides = complex carbohydrates

• Examples: Amylose, Amylopectin, Starch, Cellulose (fiber), Glycogen

General Functions of Carbohydrates

• Carbohydrate coating on the outer cell membrane

• ECM component glycocalyx

• If carbohydrates are insufficient, proteins and fatty acids will be consumed, leading to ketosis.

• Found between joints, provide cushioning and lubrication.

• Ribose sugar is used to produce B vitamin riboflavin

Fiber

• Fiber is an indigestible form of glucose.

• Soluble Fiber:

  • Found within plant cells.

  • Broken down by bacteria in the large intestine.

  • Serves as a food source.

  • Examples: Pectin, xanthan gum

• Insoluble Fiber:

  • Makes up plant cell walls.

  • Not digested.

  • Adds bulk to feces, easing elimination.

• Slows glucose absorption into the blood.

Regulation of Blood Glucose

• Insulin:

  • Responds to elevated blood glucose.

  • Stimulates organs to take up glucose from the blood.

• Glucagon:

  • Responds to low blood glucose.

  • Stimulates glycogenolysis and glucose release into blood.

Lipids: Triglycerides and Fatty Acids

• Triglyceride: glycerol + fatty acids

• Saturated Fatty Acids:

  • Straight chains.

  • Solid at room temperature.

• Unsaturated Fatty Acids:

  • Double bond, kink in the chain.

  • Liquid at room temperature.

Trans Fatty Acids

• Produced through hydrogenation.

• Make an unsaturated fat behave like saturated fat.

• Extend shelf life.

• Increase risk for heart disease.

Lipids: Phospholipids

• Similar to triglycerides, but the third fatty acid is replaced by a phosphate group and head group.

• Amphipathic molecules.

• Effective emulsifiers.

• Example: soy lecithin (phosphatidylcholine).

Lipids: Sterols

• Sterols: a class of steroid found naturally in plant and animal cells

• Example: cholesterol (non-essential nutrient, elevated levels increase the risk for coronary disease).

• Plant sterols decrease cholesterol absorption.

General Functions of Lipids

• Components of cell membranes (phospholipids, cholesterol).

• Form the myelin sheath around neurons.

• Absorption of fat-soluble vitamins (E, D, A, K).

• Vitamin production (Vitamin D).

• Protective function (padding around organs via adipose tissue).

• Energy (9 kcals/gram).

Lipid Transportation

1. Lipid absorption and processing into chylomicrons.

2. Lipoprotein lipase breaks down lipids in chylomicrons.

3. Chylomicron remnants go to the liver.

4. VLDLs transport triglycerides to body cells.

5. VLDL remnants go to the liver or are converted to LDLs.

6. LDL delivers cholesterol to body cells.

7. HDLs return cholesterol to the liver.

Metabolic Syndrome

• Main cause: Insulin resistance

  • Muscles, fat, and the liver don't respond well to insulin.

  • Can't take up glucose from the blood.

  • Pancreas makes more insulin (hyperinsulinemia)

• Conditions that increase disease risk:

  • Cardiovascular disease, atherosclerosis

  • Type 2 diabetes

  • Stroke

  • Obesity

  • Fatty liver disease

  • Polycystic ovary syndrome (PCOS)

Metabolic Syndrome Criteria

• Must have at least 3 of the following:

  • Excess abdominal weight:

    • Waist circumference >40 inches in males, >35 inches in females

  • Hypertriglyceridemia:

    • Triglyceride levels >150 mg/dL

  • Low HDL cholesterol:

    • <40 mg/dL in males, <50 mg/dL in females

  • Elevated blood sugar:

    • Fasting blood glucose ≥ 100 mg/dL

  • High blood pressure:

    • Systolic ≥ 130 mmHg

    • Diastolic ≥ 85 mmHg

Focus on Disease: Blood Lipid Levels and Atherosclerosis

• Blood lipid panels check total cholesterol, LDL, HDL, and triglycerides.

• Increased cholesterol, LDL, and triglycerides increase the risk for heart disease and atherosclerosis.

• Atherosclerosis: fatty plaques on artery walls due to increased cholesterol and triglycerides.

• Plaques narrow the lumen, leading to blood clots, heart attack, or stroke.

• Lipid Level Recommendations:

  • Cholesterol (mg/dL):

    • Low risk/optimal: <200

    • Borderline high: 200-239

    • High risk: $\geq$$$\geq$$240

  • LDL (mg/dL):

    • Low risk/optimal: <100

    • Near optimal: 100-129

    • Borderline high: 130-159

    • High risk: $\geq$$$\geq$$160

  • HDL (mg/dL):

    • Low risk/optimal: $\geq$$$\geq$$60

    • High risk: <40

  • Triglycerides (mg/dL):

    • Low risk/optimal: <150

    • High risk: $\geq$$$\geq$$150

Proteins and Amino Acids

• Proteins: assembled using 20 amino acids.

• Amino acids:

  • Essential: must be consumed.

  • Non-essential: produced by the body.

  • Conditionally-essential: non-essential made from essential when diet is limited.

• Essential Amino Acids: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine

• Non-essential Amino Acids: Alanine, Arginine, Asparagine, Aspartic acid, Cysteine, Glutamic acid, Glycine, Proline, Serine, Tyrosine

• Conditionally essential amino acids: Arginine, Cysteine, Glycine, Proline, Tyrosine

Functions of Proteins

• Structural components of cells (hair, skin, nails, ligaments, tendons).

• Enzymes.

• Chemical messengers (hormones).

• Transport lipids and lipid-soluble vitamins.

• Transport nutrients, growth factors, and waste products.

• Produce cytokines and antibodies for the immune system.

• Form actin and myosin filaments in muscle tissue.

• Help maintain fluid balance.

Classes of Vitamins

• Water-soluble: Vitamin C, Thiamin, Riboflavin, Niacin, Biotin, Pantothenic acid, Vitamin B6, Folate, Vitamin B12

• Lipid-soluble: Vitamin A, Vitamin D, Vitamin E, Vitamin K

Main Functions of Vitamins

• Act as coenzymes.

  • B vitamins function as coenzymes in metabolic reactions (glucose, amino acids, and/or fatty acids into ATP).

• Act as antioxidants.

  • Vitamin E can act as an antioxidant, neutralizing free radicals.

Minerals

• Inorganic components of the diet.

• Build structural components of the body.

• Regulate body processes.

• Major minerals (consume >100 mg/day).

• Trace minerals (consume <100 mg/day).

Main Functions of Minerals

• Electrolytes: Sodium, potassium, chloride

  • Maintain fluid balance, generate/conduct action potentials.

  • Elevated sodium leads to hypertension.

• Bone Health: Calcium, phosphorus, fluoride, magnesium, and sodium

  • Bone requires continuous mineral intake.

  • Bone loss leads to osteoporosis.

Water

• Solvent for organic molecules in metabolic reactions.

• Component of tears and synovial fluid (lubricant).

• Component of cerebrospinal fluid (cushions and supports the brain).

• Component of sweat (helps maintain body temperature).

• Regulates blood volume.

Dietary Guidelines Using MyPlate

• Balances calorie intake with output.

• Encourages nutrient-dense foods.

• Emphasizes proportionality, whole grains, lean meat/fish, low-fat dairy, healthy oils, variety, and moderation.

Implementing Guidelines Using Nutrition Labels

1. Start Here

2. Check Calories

3. Limit These Nutrients (Total Fat, Saturated Fat, Trans Fat, Cholesterol, Sodium) to % DV

   • 5% or less is low

4. Get Enough of These Nutrients (Vitamin A, Vitamin C, Calcium, Iron)

   • 20% or more is high

5. Footnote

6. Quick Guide

7. Ingredients List

Energy Intake vs. Energy Expenditure

• Energy intake must be balanced with energy output.

• Energy needs:

  • Calories to stay alive

  • Calories for daily tasks

  • Calories for physical activity

• Energy consumption > intake: weight loss

• Energy intake > consumption: weight gain

Predicting Estimated Energy Requirement (EER)

• Total energy requirements are based on:

  • Basal Metabolic Rate (BMR): minimal energy expenditure to keep you alive (60-75% of daily energy expenditure).

  • Thermic Effect of Food (TEF): energy to digest, absorb, and metabolize food (10% of daily expenditure).

  • Physical Activity: the most variable form of energy expenditure.

• EER Prediction Equations:

  • Boys 9-18 years: $88.5 – (61.9 \times age in yrs.) + PA [(26.7 \times weight in kg) + (903 \times height in m)] + 25$$$88.5 – (61.9 \times age in yrs.) + PA [(26.7 \times weight in kg) + (903 \times height in m)] + 25$$

  • Girls 9-18 years: $135.3 – (30.8 \times age in yrs.) + PA [(10.0 \times weight in kg) + (934 \times height in m)] + 25$$$135.3 – (30.8 \times age in yrs.) + PA [(10.0 \times weight in kg) + (934 \times height in m)] + 25$$

  • Men $\geq$$$\geq$$ 19 years: $662 – (9.53 \times age in yrs.) + PA [(15.91 \times weight in kg) + (539.6 \times height in m)]$$$662 – (9.53 \times age in yrs.) + PA [(15.91 \times weight in kg) + (539.6 \times height in m)]$$

  • Women $\geq$$$\geq$$ 19 years: $354 – (6.91 \times age in yrs.) + PA [(9.36 \times weight in kg) + (726 \times height in m)]$$$354 – (6.91 \times age in yrs.) + PA [(9.36 \times weight in kg) + (726 \times height in m)]$$

Appetite vs. Hunger

• Appetite: desire to consume food, with a variety of triggers.

• Hunger: physiological need for food.

• Hunger signals triggered by hormones (ghrelin, peptide YY).

• Leptin regulates adipose tissue levels.

Absorptive State

1. Nutrients absorbed from the small intestine, blood glucose rises.

2. Pancreas produces insulin, stimulating cells to absorb glucose (liver, muscle, adipose tissue).

3. Liver: excess glucose converted to glycogen.

4. Muscle: excess glucose converted to glycogen; amino acids build contractile proteins.

5. Adipose tissue: excess lipids stored.

Post-Absorptive State

1. No nutrients entering the bloodstream.

2. Pancreas releases glucagon, targeting liver, muscle, and adipose tissue.

3. Liver: glycogenolysis and lipolysis, releasing glucose and lipids into the blood.

4. Muscle: amino acids from protein breakdown, glucose released into the blood.

5. Adipose tissue: release of stored lipids.

Anaerobic Respiration: Glycolysis

• Glycolysis occurs in the cytoplasm.

• Glucose is converted into pyruvate.

• Net gain: 2 ATP

• Pyruvate is shuttled to mitochondria for pyruvate oxidation.

Aerobic Respiration: Pyruvate Oxidation

• Net gain: 0 ATP

• Acetyl groups are shuttled into the citric acid cycle.

Aerobic Respiration: Citric Acid Cycle

• Acetyl coenzyme A enters the cycle.

• Acetyl groups are further oxidized.

Aerobic Respiration: Electron Transport Chain

• Electrons are transported along the chain.

• ATP synthase produces ATP.

• Final electron acceptor.

• Produces ATP in substantial amounts.

Metabolism of Fatty Acids: Beta-Oxidation

• $\beta$$$\beta$$-oxidation of fatty acids

Metabolism of Proteins: Deamination

• Deamination

Continuation of Glycolysis Under Constant Anaerobic Conditions

• Lactic acid fermentation allows small amounts of ATP to be generated

• Regeneration allows glycolysis to continue