Nutrition Lecture Vocabulary

Nutrients and Their Functions

Types of Nutrients

Nutrients are substances that provide energy and building blocks for the body. They are classified as:

• Macronutrients: Needed in large quantities (g-kg). Include carbohydrates, lipids (fats), proteins, and water.
• Micronutrients: Needed in small quantities (μg-mg). Include vitamins and minerals.
• Organic Nutrients: Carbon-based molecules. Examples include carbohydrates, lipids, proteins, and vitamins.
• Inorganic Nutrients: Non-carbon-based molecules. Examples include water and minerals.
• Essential Nutrients: Cannot be produced by the body and must be obtained from the diet.
• Non-Essential Nutrients: Can be produced by the body.

Energy from Nutrients

• Energy in nutrients is measured in calories.
• 1 \text{ calorie} = the energy required to raise the temperature of 1 mL of water by 1°C.
• 1 \text{ Calorie (kcal)} = 1000 \text{ calories}

• Alcohol is not considered a nutrient but has caloric value.

Nutrients as Building Blocks

• Lipids, carbohydrates, and proteins are crucial for cellular processes.
• Calcium and proteins from milk are essential for building bones, hair, teeth, and muscle.
• Vitamin D enhances calcium absorption.
• Vitamin D deficiency can lead to rickets.
• Vitamin A is necessary for light receptors in the retina.

Nutrients in Regulating Body Processes

• B vitamins are involved in chemical reactions to produce ATP (energy).
• Vitamin B12 is required for red blood cell production.
• Water helps maintain blood volume.
• Proteins, carbohydrates, and lipids can function as hormones (for cellular communication).
• Proteins also act as enzymes in cellular reactions.

Carbohydrates

Types and Structures of Carbohydrates

• Monosaccharides: Simple carbohydrates, such as glucose, fructose, and galactose.

  • Glucose: \text{C}6\text{H}{12}\text{O}_6 with a specific ring structure.
  • Fructose: \text{C}6\text{H}{12}\text{O}_6 with a different ring structure than glucose.
  • Galactose: \text{C}6\text{H}{12}\text{O}_6 with a ring structure differing from glucose and fructose.

• Disaccharides: Simple carbohydrates formed by two monosaccharides.

  • Sucrose: Glucose + Fructose
  • Lactose: Galactose + Glucose
  • Maltose: Glucose + Glucose

• Polysaccharides: Complex carbohydrates.

  • Amylose: A form of starch.
  • Amylopectin: Another form of starch.
  • Starch: A mixture of amylose and amylopectin.
  • Cellulose (fiber): Indigestible form of glucose.
  • Glycogen: Storage form of glucose in animals.

General Functions of Carbohydrates

• Component of cell membranes.
• Component of the extracellular matrix (glycocalyx).
• If carbohydrates are insufficient, the body will consume proteins and fatty acids, leading to ketosis.
• Act as cushioning and lubrication between joints.
• Ribose sugar is used to produce Vitamin B riboflavin.

Fiber

• Fiber: An indigestible form of glucose.
• Soluble Fiber:
  • Found within plant cells.
  • Broken down by bacteria in the large intestine.
  • Serves as a food source for gut bacteria.
  • Examples: Pectin, xanthan gum.
• Insoluble Fiber:
  • Makes up plant cell walls.
  • Not digested by the body or intestinal bacteria.
  • Adds bulk to feces, aiding elimination.
• Fiber slows the absorption of glucose into the blood.

Regulation of Blood Glucose

• Insulin:
  • Responds to elevated blood glucose levels.
  • Stimulates organs to take up glucose from the blood for fuel.
• Glucagon:
  • Responds to low blood glucose levels.
  • Stimulates glycogenolysis (breakdown of glycogen) and glucose release into the blood.

Lactose Intolerance

• What is it? Inability to break down lactose, the main sugar in milk.
• What causes it? Low expression of the enzyme lactase in the small intestine.
• Symptoms: Cramping, diarrhea caused by lactose breakdown in the large intestine.
• Treatment: Synthetic lactase (Lactaid®) can be taken or used to treat dairy products.

Lipids

Types of Lipids

• Triglycerides:
  • Glycerol backbone chemically bonded to fatty acids.
  • Saturated Fatty Acids:
    • Form straight chains of carbon atoms that can be easily packed together.
    • Solid at room temperature.
  • Unsaturated Fatty Acids:
    • Have a double bond that creates a kink in the fatty acid chain.
    • Liquid at room temperature.
  • Trans Fatty Acids:
    • Produced through hydrogenation (changing the position of hydrogen atoms around a double bond).
    • Make an unsaturated fat behave more like a saturated fat.
    • Developed by food manufacturers to extend shelf life.
    • Associated with increased risk of heart disease.
• Phospholipids:
  • Similar to triglycerides, but one fatty acid is replaced by a phosphate group and a specific head group.
  • Amphipathic molecules (have both hydrophobic and hydrophilic regions).
  • Effective emulsifiers (allow oil and water to mix).
  • Example: Soy lecithin (phosphatidylcholine).
• Sterols:
  • Steroids found naturally in plant and animal cells.
  • Example: Cholesterol (non-essential nutrient; elevated levels increase risk for coronary disease).
  • Plant sterols decrease cholesterol absorption from animal-based foods.

General Functions of Lipids

• Components of cell membranes (phospholipids, cholesterol).
• Form the myelin sheath that surrounds and protects neurons.
• Absorption of fat-soluble vitamins (Vitamins E, D, A, K).
• Vitamin production (Vitamin D).
• Protective padding around organs.
• Energy source (9 kcals/gram).
• Adipose tissue acts as padding around organs.

Transportation of Lipids

1. Lipid absorption and processing into chylomicrons, which travel through lymphatic vessels into the blood.
2. Blood vessel endothelial cells use lipoprotein lipase to break down lipids in chylomicrons into fatty acids and glycerol, which enter cells.
3. Leftover chylomicron pieces go to the liver for degradation.
4. VLDLs (Very Low-Density Lipoproteins) transport triglycerides to body cells.
5. Leftover VLDL pieces go to the liver for degradation or are converted to LDLs (Low-Density Lipoproteins).
6. LDL binds LDL receptors on body cells and are endocytosed, delivering cholesterol.
7. HDLs (High-Density Lipoproteins) return unused cholesterol back to the liver, where it is broken down and recycled.

Metabolic Syndrome

• Main cause: Insulin resistance.
  • Muscles, fat, and liver don't respond well to insulin and can't take up glucose from the blood.
  • Pancreas is forced to produce more insulin, leading to hyperinsulinemia.
• A group of conditions that increase the risk of:
  • Cardiovascular disease
  • Atherosclerosis
  • Type 2 diabetes
  • Stroke
  • Obesity
  • Fatty liver disease
  • Polycystic ovary syndrome (PCOS)
• Must have at least 3 of the following criteria:
  • Excess abdominal weight: Waist circumference >40 inches in males and >35 inches in females.
  • Hypertriglyceridemia: Triglyceride levels >150 mg/dl.
  • Low levels of HDL cholesterol: <40 mg/dl in males and <50 mg/dl in females.
  • Elevated blood sugar levels: Fasting blood glucose of <40 mg/dl (Note: There seems to be a typo here, and it should likely be a higher value).
  • High blood pressure: Systolic 130 mmHg or higher, or Diastolic 85 mmHg or higher.

Blood Lipid Levels and Atherosclerosis

• Blood lipid panels check for total cholesterol, LDL, HDL, and triglycerides.
• Increased levels of cholesterol, LDL, and triglycerides are associated with increased risk for heart disease and atherosclerosis.
• Atherosclerosis: Fatty plaques are deposited on the inside of the artery wall due to increased cholesterol and triglycerides.
• Growing plaques cause lumen narrowing, potentially leading to a blood clot and heart attack or stroke.

Proteins

Types of Proteins

• Proteins are assembled in the cell using combinations of 20 different amino acids.
• Amino acids can be:
  • Essential: Must be consumed in the diet.
  • Non-essential: Produced by the body.
  • Conditionally-essential: Non-essential amino acids made from essential amino acids that are limited in the diet.

• Conditionally essential amino acids.

Functions of Proteins

• Structural components of cells (hair, skin, nails, ligaments, tendons).
• Function as enzymes.
• Transport chemical messengers (hormones).
• Transport lipids and lipid-soluble vitamins.
• Transport nutrients, growth factors, and waste products across cell membranes.
• Produce cytokines and antibodies for the immune system.
• Form actin and myosin filaments in muscle tissue.
• Help maintain fluid balance between blood and tissue.

Vitamins

Classes of Vitamins

Main Functions of Vitamins

• Act as coenzymes in metabolic reactions.
  • E.g., B vitamins function as coenzymes in reactions that convert glucose, amino acids, and fatty acids into ATP.
• Act as antioxidants.
  • Free radicals: Generated during aerobic respiration, can damage molecular structures.
  • Vitamin E can act as an antioxidant, neutralizing free radicals.

Minerals

Main Functions of Minerals

• Inorganic components of the diet.
• Function in building structural components of the body.
• Regulate different body processes.
• Can be major minerals (need to consume more than 100 mg/day) or trace minerals (need to consume less).

Electrolytes

• Charged ions that conduct an electrical current in solution (e.g., sodium, potassium, chloride).
• Maintain fluid balance and generate/conduct action potentials.
• Elevated sodium in the diet can lead to hypertension (high blood pressure).

Bone Health

• Inorganic component of bone matrix contains minerals like calcium, phosphorus, fluoride, magnesium, and sodium.
• Bone is a living tissue requiring continuous mineral intake.
• Bone loss can lead to osteoporosis.

Water

Functions of 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

MyPlate

• Balances calorie intake with output.
• Encourages nutrient-dense foods.
• Emphasizes:
  • Proportionality
  • Whole grains
  • Lean meat/fish
  • Low-fat dairy
  • Healthy oils
  • Variety, moderation

Nutrition Labels

1. Start here
2. Check calories
3. Limit these nutrients
4. Get enough of these nutrients
5. Footnote
6. Quick guide to % Daily Value (DV):
   • 5% or less is low
   • 20% or more is high

Energy Balance

• To maintain a healthy diet: energy intake must be balanced with energy output.
• Energy needs include:
  • Calories needed to stay alive
  • Calories needed for daily tasks
  • Calories needed for extra physical activity
• Energy consumption > intake: weight loss
• Energy intake > consumption: weight gain

Estimated Energy Requirement (EER)

Total energy requirements are based on:

• Basal metabolic rate (BMR): Minimal energy expenditure to keep you alive; represents 60-75% of daily energy expenditure.
• Thermic effect of food (TEF): Energy required to digest, absorb, and metabolize food; represents 10% of daily expenditure.
• Physical activity: Most variable form of energy expenditure.

EER Prediction Equations:

• Boys (9-18 years): 88.5 – (61.9 \times \text{age in yrs.}) + PA [(26.7 \times \text{weight in kg}) + (903 \times \text{height in m})] + 25
• Girls (9-18 years): 135.3 – (30.8 \times \text{age in yrs.}) + PA [(10.0 \times \text{weight in kg}) + (934 \times \text{height in m})] + 25
• Men (>= 19 years): 662 – (9.53 \times \text{age in yrs.}) + PA [(15.91 \times \text{weight in kg}) + (539.6 \times \text{height in m})]
• Women (>= 19 years): 354 – (6.91 \times \text{age in yrs.}) + PA [(9.36 \times \text{weight in kg}) + (726 \times \text{height in m})]

Where PA (Physical Activity) values are:

• Sedentary: 1.00
• Low active: 1.11-1.16
• Active: 1.25-1.31
• Very active: 1.42-1.56

Example: Active 24-year-old woman, 56.8 kg, 1.65 m tall:

EER = 354 – (6.91 \times 24) + 1.27 [(9.36 \times 56.8) + (726 \times 1.65)] = 2385 \text{ kcal/day}

Appetite vs. Hunger

• Appetite: Desire to consume food, trigged by various factors.
• Hunger: Physiological need for food.
• Hunger signals triggered by hormones like ghrelin and peptide YY.
• Leptin regulates the amount of adipose tissue in the body.

Absorptive State

1. Nutrients absorbed from the small intestine into the blood; blood glucose levels rise.
2. Pancreas produces insulin in response to high blood glucose. Insulin stimulates cells to absorb glucose from the blood, targeting liver, muscle, and adipose tissue.
3. Liver: Excess glucose converted to glycogen. Muscle: Excess glucose converted to glycogen; amino acids used to build contractile proteins. Adipose tissue: Excess lipids are stored.

Post-Absorptive State

1. No nutrients are entering the bloodstream.
2. Pancreas releases glucagon in response to low blood glucose. Glucagon targets the liver, muscle, and adipose tissue.
3. Liver: Glycogenolysis and lipolysis, leading to the release of glucose and lipids into the blood. Muscle: Amino acids formed by the breakdown of contractile proteins; glucose released into the blood. Adipose tissue: Release of stored lipids.

Anaerobic Respiration: Glycolysis

• Occurs in the cytoplasm.
• Glucose is converted into pyruvate.
• Net gain: 2 ATP
• Pyruvate is then shuttled to the mitochondria for pyruvate oxidation.

Aerobic Respiration: Pyruvate Oxidation

• Pyruvate is converted into acetyl coenzyme A.
• Net gain: 0 ATP
• Acetyl groups are shuttled into the citric acid cycle.

Aerobic Respiration: Citric Acid Cycle

• Acetyl groups are further oxidized.

Aerobic Respiration: Electron Transport Chain

• Electrons are transported, leading to ATP production.
• Final electron acceptor: Oxygen.
• Produces ATP in substantial amounts.

Metabolism of Fatty Acids: Beta-Oxidation

Fatty acids are broken down into acetyl-CoA molecules, which can then enter the citric acid cycle.

Metabolism of Proteins: Deamination

Amino acids are deaminated (removal of the amine group), and the carbon backbone can be used for energy or glucose production.

Glycolysis under Anaerobic Conditions: Lactic Acid Fermentation

• Pyruvate is converted to lactic acid.
• Allows small amounts of ATP to be generated.
• Regeneration of NAD+ allows glycolysis to continue.