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Carbohydrates
Protein sparing, meaning if there aren’t enough carbs in the diet, the body will convert protein into protein into glucose to meet energy needs.
Definition: Carbohydrates are "hydrated carbons" – for every carbon atom, there is one molecule of water.
Primary Fuel Source: Carbohydrates are the body's main source of energy, especially for the CNS, brain, and red blood cells.
Energy Content: Carbs provide 4 calories per gram.
Glucose: The carbohydrate we consume is converted into glucose, which is transported through the blood as "blood sugar." It is stored as glycogen in muscles and the liver.
Excess Carbohydrates: When carbs are consumed in excess, they are converted and stored as fat.
Blood Glucose Regulation:
Insulin: Lowers blood glucose levels.
Glucagon: Increases blood glucose levels.
Blood Glucose Levels
Normal: 70–99 mg/dL
Pre-Diabetes: 100–125 mg/dL
Diabetes: 126+ mg/dL
Hypoglycemia: Low blood glucose levels (<70 mg/dL)
Hyperglycemia: High blood glucose levels (>100 mg/dL)
Types of Carbohydrates
Monosaccharides
Disaccharides
Oligosaccharides
Polysaccharides
Glycogen
Monosaccharides
Single sugar molecules.
Fructose: Known as "fruit sugar," found in fruits, vegetables, honey, and high-fructose corn syrup.
Galactose: Most commonly consumed as part of lactose in dairy.
Disaccharides
Two monosaccharides linked together.
Maltose: Glucose + Glucose (alpha bond), found in sprouting seeds and malted beverages.
Sucrose: Glucose + Fructose (alpha bond), known as "table sugar," found in sugarcane, sugar beets, and maple syrup.
Lactose: Glucose + Galactose (beta bond), found in dairy products.
Oligosaccharides
Complex carbohydrates made up of 3 to 10 monosaccharides.
Fructans/Fructo-oligosaccharides – Chains of fructose with glucose at the end.
Galactans/Galacto-oligosaccharides – Chains of galactose with glucose at the end.
Raffinose – A trisaccharide composed of galactose, glucose, and fructose.
Stachyose – A tetrasaccharide composed of two galactose, one glucose, and one fructose.
Oligosaccharides act as fiber and prebiotics since we cannot digest them
Fructans/Fructo-oligosaccharides
Chains of fructose with glucose at the end
Galactans/Galacto-oligosaccharides
Chains of galactose with glucose at the end
Raffinose
A trisaccharide composed of galactose, glucose , and fructose
Stachyose
A tetrasaccharide composed of two galactose, one glucose, and one fructose
Lactose Intolerance
Cause: Insufficient lactase enzyme production, which decreases after childhood (around 3-5 years old).
Symptoms: Undigested lactose attracts water into the GI tract and is fermented by bacteria, causing gas, bloating, cramping, and diarrhea.
Primary Lactose Intolerance: Natural decline in lactase production with age.
Secondary Lactose Intolerance: Caused by diseases (e.g., Crohn's or Celiac disease) that damage lactase-producing cells.
Management: Some people can tolerate low-sugar dairy (e.g., hard cheeses, yogurt), as the lactose is broken down during fermentation.
Polysaccharides
Complex carbohydrates composed of multiple sugar units.
Digestible Polysaccharides (Starch)
Amylose – Linear and unbranched; glucose linked by alpha 1-4 bonds.
Amylopectin – Highly branched; glucose linked by alpha 1-4 and alpha 1-6 bonds.
Indigestible Polysaccharides (Fiber)
Soluble Fiber – Dissolves in water, becomes gel-like, and is fermented by probiotics.
Aids in blood sugar control.
Lowers blood cholesterol levels.
Acts as a prebiotic, promoting gut health and diversity.
Promotes satiety and aids in weight control.
Insoluble Fiber – Does not dissolve in water and is not fermented by probiotics.
Promotes bowel regularity.
Adds bulk to stool and prevents constipation.
Promotes satiety and aids in weight control.
Amylose
Linear and unbranched; glucose linked by alpha 1-4 bonds. (Digestible polysaccharide: aka Starch)
Amylopection
Highly branched; glucose linked by alpha 1-4 and alpha 1-6 bonds. (Digestible Polysaccharides: Aka Starch)
Soluble FIber
Dissolves in water, becomes gel-like, and is fermented by probiotics
Aids in blood sugar control.
Lowers blood cholesterol levels.
Acts as a prebiotic, promoting gut health and diversity.
Promotes satiety and aids in weight control.
Indigestible Polysaccharides (Fiber)
Insoluble FIber
Does not dissolve in water and is not fermented by probiotics.
Promotes bowel regularity.
Adds bulk to stool and prevents constipation.
Promotes satiety and aids in weight control.
Indigestible Polysaccharide (fiber)
Glycogen
Storage Form of Glucose in Humans
Structure is similar to amylopectin, with glucose linked by alpha bonds.
Liver glycogen – Maintains blood sugar levels.
Muscle glycogen – Used by muscles for energy.
Sugar Alcohols
Also known as Polyols or Polyhyrdric Alcohols
Contain an -OH (hydroxyl) group.
Common sugar alcohols: Sorbitol, Mannitol, Xylitol, Erythritol, Maltitol.
Often end in "-ol."
FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols).
FODMAPs produce gas.
Consuming sugar alcohols in large amounts may cause gas, bloating, and GI distress.
Foods containing sorbitol or mannitol must include a warning on their label:
“Excess consumption may have a laxative effect.”
FODMAPS
Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols.
FODMAPS Produce gas
May cause bloating, gas, and GI distress
***Foods containing sorbitol or mannitol must include a warning on their label: “Excess consumption may have a laxative effect.”
Sweeteners
Nutritive Sweeteners – Provide calories.
Non-Nutritive Sweeteners – Do not provide calories (e.g., artificial sweeteners).
Extremely sweet and calorie-free.
FDA-approved artificial sweeteners recognized as safe:
Saccharin
Aspartame
Sucralose
Neotame
Acesulfame-Potassium
Advantame
Nutritive Sweeteners
Provide calories
Non-Nutritive Sweeteners
Do not provide calories (artificial sweeteners)
FDA approved artificial Sweeteners
Saccharin
Aspartame
Sucralose
Neotame
Acesulfame-Potassium
Advantame
Orthorexia
An unhealthy obsession with healthy eating
Functions of Carbohydrates
Primary source of energy for the body
Brain/CNS prefers glucose as an energy source
Carbohydrates spare protein, preserving body protein/muscle
Prevents ketosis (excessive ketone production from fat breakdown)
Ketones: Alternative energy source formed from fatty acids (acidic)
Ketones
Alternative energy source formed from fatty acids (acidic)
Carbohydrate Digestion and Absorption
Mouth – Salivary amylase begins breaking starch into polysaccharides and disaccharides
Stomach – No carbohydrate digestion (amylase inactivated by stomach acid)
Pancreas – Releases pancreatic amylase and dextrinase to break starch into disaccharides
Small Intestine – Enzymes break disaccharides into monosaccharides, which are absorbed
Liver – Monosaccharides travel via the portal vein to the liver
Large Intestine – Some soluble fiber is fermented into acids and gases
Rectum/Anus – Insoluble fiber is excreted in feces
Mouth
Salivary amylase begins breaking starch into polysaccharides and disaccharides
Stomach
No carbohydrate digestion (amylase inactivated by stomach acid)
Pancreas
Releases pancreatic amylase and dextrinase to break starch into disaccharides
Small Intestine
Enzymes break disaccharides into monosaccharides, which are absorbed
Liver
Monosaccharides travel via the portal vein to the liver
Large Intestine
Some soluble fiber is fermented into acids and gases
Rectum/Anus
Insoluble fiber is excreted in feces
Glucose & Galactose
Actively absorbed (requires ATP)
Fructose
Slowly diffuses across the GI Tract
Non-glucose monosaccharides
In the Liver non-glucose monosaccharides are converted to glucose and glucose can be released into the bloodstream, stored as glycogen, and converted to fat.
Fiber
Binds minerals in the digestive tract
Recommended Intake:
Before age 50: 25g/day (women), 38g/day (men)
After age 50: 21g/day (women), 30g/day (men)
Adequate Intake: 14g per 1000 kcal
High Fiber Risks:
Low liquid intake → Constipation
Insufficient calorie intake → Micronutrient deficiencies
Early satiety → Can limit overall nutrient intake
Blood Glucose Regulation
Organs Involved:
Liver: Determines glucose release into bloodstream, stores excess as glycogen
Pancreas: Releases hormones for blood glucose regulation
Key Hormones:
Insulin (Anabolic Hormone):
Lowers blood glucose levels (facilitates glucose uptake into cells)
Acts as a "key" for glucose entry into cells
Glucagon:
Increases blood glucose by breaking down glycogen
Stimulates glucose production from non-carbohydrate sources
Other Hormones That Raise Blood Glucose:
Cortisol, Epinephrine, Norepinephrine, Growth Hormone
Insulin (Anabolic Hormone)
Lowers blood glucose levels (Facilitates glucose uptake into cells
Acts as a key for glucose entry into cells
Glucagon
Increases blood glucose by breaking down glycogen
Stimulates glucose production from non-carbohydrate sources
Other Hormones that Raise Blood Glucose
Cortisol
Epinephrine
Norepinephrine
Growth Hormone
Dietary Carbohydrate Recommendations
RDA: 130g/day
Supplies adequate glucose for the brain/CNS
Prevents excessive ketone production
AMDR: 45-65% of total energy intake
Athletes/Active Individuals: Should consume a higher proportion of carbs
Added Sugar:
Limit to ≤10% of total daily energy intake
Type 1 Diabetes (5% of cases)
Cause: Autoimmune destruction of pancreatic cells
Symptomes
Ketosis: Ketones are formed from fatty acids and are an alternative energy source for the body (Ketones are acidic)
Weight loss
Increased thirst, hunger, urination
Fruity/acetone breath
Treatment:
Insulin therapy
Diet & exercise
Monitor: Blood glucose, urine ketones, HbA1c
Type 2 Diabetes (90% of cases)
Cause: Insulin resistance
Symptoms:
Fatigue
Nighttime urination
Ketosis usually absent
Treatment:
Exercise & Diet
Oral medication to lower blood glucose
Monitor: Blood glucose, HbA1c
Glycemic Index (GI)
Ranks carbs (0-100) based on their impact on blood sugar
High Gi foods—>Rapid blood sugar spike
Glycemic Load (GL)
Takes into account both carbohydrate quantity and quality
Low GL meals —> Better blood sugar control
Functions of Lipids
Energy source (9 kcal/g)
Insulation & protection (preserve body heat, protect organs)
Aid in absorption & transport of fat-soluble vitamins (A, D, E, K)
Structural component of cells & hormones
Enhance food flavor and texture
Types of Lipids
Triglycerides (most common in food & body)
Composed of glycerol + 3 fatty acids
Phospholipids (major component of cell membranes)
Sterols (e.g., cholesterol)
Fatty Acid Types
Saturated Fatty Acids (SFA) – No double bonds (solid at room temp)
Found in meat, dairy, coconut oil, palm oil
Monounsaturated Fatty Acids (MUFA) – One double bond
Found in olive oil, avocado, nuts
Polyunsaturated Fatty Acids (PUFA) – Two or more double bonds
Includes Omega-3 (EPA, DHA) and Omega-6
Found in fish, flaxseeds, walnuts
Fatty Acid Length
Long-Chain FA (>12 C): Beef, pork, lamb, fish, plant oils (slow digestion)
Medium-Chain FA (6-10 C): Coconut oil, dairy (rapid digestion)
Short-Chain FA (<6 C): Butter, gut-fermented fiber (quick digestion)
Lipid Metabolism Processes
Esterification: Formation of triglycerides
De-esterification: Release of fatty acids (hydrolysis)
Re-esterification: Reattachment of fatty acids
Recommended Fat Intake
No RDA (Recommended Dietary Allowance) for adults
AI (Adequate Intake) established for infants
AMDR (Acceptable Macronutrient Distribution Range): 20-35% of total kcal
Omega-3 Adequate Intake (as ALA)
Males (19-50 years old): 1.6 g
Females (19-50 years old): 1.1 g
Dietary Guidelines for Americans (DGAs):
Consume more unsaturated fats
Limit saturated fat to <10% of total calories
Avoid artificial trans fats
Saturated Fat
Sources
Animal Products (butter, ghee, lard, red meat, dairy)
Tropical oils (coconut oil, palm oil, palm kernel oil)
Baked goods & Ultra processed foods
Monounsaturated Fat (MUFA)
Sources
Plant-based oils (olive oil, canola oil, peanut oil, avocado oil)
Whole foods (olives, avocados, nuts, seeds, nut butters)
Polyunsaturated Fat (PUFA)
Sources
Plant oils (safflower, sunflower, corn, soybean)
Nuts & seeds (walnuts, flaxseeds, chia seeds)
Fish & seafood (salmon, mackerel, sardines)
Trans Fat
Naturally found in dairy
Artificial sources: Partially hyrogenated oils, fast food, fried food
PHOs (Partially Hydrogenated Oils) banned in 2020
Essential Fatty Acids (EFAs)
Body cannot synthesize EFAs—> Must come from food
Alpha-Linolenic Acid (ALA) (18:3) w3)- Omega 3 PUFA
Linoleic Acid (LA) (18:2 w6)- Omega-6 PUFA
Alpha-Linolenic Acid (ALA) (18:3 ω3) – Omega-3 PUFA
Used to make: EPA & DHA + certain eicosanoids
Sources: Nuts, seeds, flaxseed oil, chia seeds, walnuts, canola oil, soy-based foods
Linoleic Acid (LA) (18:2 ω6) – Omega-6 PUFA
Used to make: Arachidonic Acid (ARA) + certain eicosanoids
Omega-3 Fatty Acids
Eicosapentaenoic Acid (EPA) (20:5 ω3)
Synthesized from ALA or obtained from diet
Needed for:
Fetal development
Healthy aging
Docosahexaenoic Acid (DHA) (22:6 ω3)
Synthesized from EPA or obtained from diet
Supports:
Brain & eye development/function
Nervous system function
Memory & cognition
Deficiency linked to: Depression, suicidal behavior, anger, hostility
Sources of EPA & DHA:
Fatty fish (herring, salmon, mackerel, sardines, trout, tuna)
Seafood (oysters, crab)
Omega-3 supplements (fish oil, krill oil, cod liver oil, algal oil)
Eicosapentaenoic Acid (EPA) (20:5 ω3)
Synthesized from ALA or obtained from diet
Needed for:
Fetal development
Healthy aging
Docosahexaenoic Acid (DHA) (22:6 ω3)
Synthesized from EPA or obtained from diet
Supports:
Brain & eye development/function
Nervous system function
Memory & cognition
Deficiency linked to: Depression, suicidal behavior, anger, hostility
Sources of EPA & DHA:
Fatty fish (herring, salmon, mackerel, sardines, trout, tuna)
Seafood (oysters, crab)
Omega-3 supplements (fish oil, krill oil, cod liver oil, algal oil)
Functions of Triglycerides
Energy source: 9 kcal/g
Main fuel source when resting or doing light activity
Body stores excess calories as fat
Protects vital organs & maintains body temperature
Aids in absorption of fat-soluble vitamins (A, D, E, K)
Transports essential nutrients in the bloodstream
Fat Cell Growth
Hypertrophy: Increase in cell size
Hyperplasia: Increase in cell number
Weight gain → Fat droplets enlarge
Weight loss → Fat droplets shrink
Phospholipids
Two major roles:
Cell membrane component
Functions as an emulsifier
Sources:
Dietary: Lecithin (egg yolks, wheat germ, peanuts)
Synthesized by the body
Unrefined plant oils (vegetable, nut, olive oil)
Structure:
Phosphate "head" – Hydrophilic
Fatty acid "tails" – Hydrophobic
In water, phospholipids form micelles
Sterols & Cholesterol
Sterols: Type of steroid (multi-ringed structure)
Best known sterol: Cholesterol
Functions of cholesterol:
Used to make steroid hormones (testosterone, estrogen)
Adrenal hormones (aldosterone, cortisol)
Cell membranes
Vitamin D
Bile acids
Sources: Found in animal-based foods or synthesized by the body
Eicosanoids: Hormone-like compounds
Regulate:
Blood pressure & clotting
Sleep/wake cycles
Body temperature
Inflammation & immune response
Kidney function & fluid balance
Omega-3-derived eicosanoids: Anti-inflammatory
Omega-6-derived eicosanoids: Pro-inflammatory
Phytosterols
Plant stanols & sterols (cholesterol-like compounds)
Function:
Lower LDL cholesterol by interfering with dietary cholesterol absorption
2 g/day can reduce LDL by 8-10%
Fatty Acid Nomenclature
Two Naming Systems:
Omega (ω) System
Methyl end (CH₃) = Omega end
Number indicates first double bond closest to methyl end
Example: Linoleic Acid (18:2 ω6)
Delta (Δ) System
Describes fatty acids from carboxyl end (COOH)
Indicates all double bond locations
Example: Linoleic Acid (18:2 Δ9,12)
Hydrogenation & Trans Fats
Hydrogenation: Process of adding hydrogen to unsaturated fats
Fully Hydrogenated Oils:
All double bonds → single bonds
Converts liquid oil → solid fat
Partially Hydrogenated Oils (PHOs):
Some double bonds → single bonds
Forms trans fats
PHOs banned in 2020 (no longer GRAS by FDA)
Lipoproteins
Lipoproteins: Transporters of Lipids in the Blood
Chylomicrons
Primary Component: Triglyceride
Key Role: Transports dietary fat from the small intestine (SI) to the cells
Very-Low-Density Lipoprotein (VLDL)
Primary Component: Triglyceride
Key Role: Produced by the liver – Carries lipids from the liver to the cells
Intermediate-Density Lipoprotein (IDL)
Low-Density Lipoprotein (LDL) – "Bad" Cholesterol
Arises from VLDL
Primary Component: Cholesterol
Key Role: Carries cholesterol made by the liver and from other sources to the cells
High-Density Lipoprotein (HDL) – "Good" Cholesterol
Primary Component: Protein
Key Role: Reverse Cholesterol Transport
Helps remove cholesterol from the cells and excretes it from the body
Can prevent LDL from being oxidized
Lipoprotein Lipase (LPL)