Macronutrients and Micronutrients (Summary)

• Macronutrients


  Carbohydrates, Lipids, and Proteins
• Glucose and glycogen are not sourced from food
• Hexose


  1. carbon ring
• Pentose


  1. carbon ring
• Sugars (Saccharides)


  • Linked either with alpha bond (starch - spiral) and beta (cellulose - linear) bonds
  • Linked through condensation (H2O molecule is released); separated through hydrolysis (H2O molecule splits the bond)
• Carbohydrates


  • Chief source of energy
  • Brain - Glucose (preferred fuel source)
  • Liver (storage/reserve) - Glucose, Glycogen, Fat
  • Stores glucose in the form of glycogen
  • Spares protein breakdown
  • Prevents ketosis
• Simple carbohydrates


  • Monosaccharide - Glucose, Galactose, Fructorse
  • Disaccharide - Sucrose, Maltose, Lactose
• Complex carbohydrates


  • Oligosaccharide - Raffinose and Stachyose
  • Polysaccharide - Glycogen (storage in animals); Starch (storage in plants, i.e., Amylose and Amyopectin) and Fibers (Soluble/Insoluble)
• Main source of carbohydrates

  Plants - produced during photosynthesis (Sugars, Starches, Fibers)
• Anatomical organs involved in carbohydrate digestion

  • Mouth
  • Stomach
  • Small Intestine
  • Large Intestine
  • Pancreas
• Carbohydrate digestion


  1. Begins digestion → Breakdown of CHO into shorter sugar units (polysacch to disacch)

  2. CHO digestion stops. Acidity of stomach juices halt action of salivary amylase and stops carbohydrate digestion

  3. Fiber is not digested - delays gastric emptying

  4. Produces an enzyme to breakdown starch, released through the pancreatic duct into the small intestine

  5. Regulates blood glucose (high glucose stimulates insulin release; low glucose stimulates release of glucagon)

  6. Most CHO digestion occurs here, P. amylase continues starch digestion

  7. Disaccharide enzymes hydrolyze disacchs into monosacchs (absorbed through the intestinal cells)

  8. Fiber is not digested - delays absorption of other nutrients

  9. Most fiber passes intact through GIT to large intestine. Bacterial enzymes digest fiber and produces short-chain FA and gas; fiber holds water, regulate bowel activity, binds substances (bile, cholesterol and some minerals)
• Enzymes/Hormones involved in carbohydrate digestion

  • Salivary Amylase
  • HCl Acid, protein-digesting enzymes
  • Pancreatic Amylase
  • Insulin
  • Glucagon
  • Pancreatic Amylase
  • Sucrase, Maltase, Lactase
  • Bacterial Enzymes
• Monosaccharides


  Glucose, Fructose, Galactose
• Absorption mechanism of monosaccharides


  • Active Transport
  • Facilitated diffusion
  • Active Transport
• Absorption site of monosaccharides

  The monosacchs pass through intestinal musocal and end enter the bloodstream. Travels to the liver by the portal vein. The liver converts fructose and galactose to glucose
• Fate of glucose in the liver

  The liver may 1) convert glucose into glycogen and store it as reserves; 2) burn it for energy; or 3) release t to the bloodstream for use in other parts
• Some negative effects of carbohydrates

  • Sugar and Dental Carries
  • Fiber and Obesity
  • Fiber and Type 2 Diabetes
  • Fiber and Cardiovascular Disease
  • Fiber and Gastrointestinal Disorders
• Lipids


  • Carbon chain with a Methyl Group and Acid (Carboxyl) end
  • Fatty Acids (determine the characteristics of a fat -- solid or liquid)
  • Chain Length, Degree of Saturation, Location of Double Bonds
  • Triglycerides - 3 FA with glycerol backbone - most predominant in food and in the body
  • Phospholipids - glycerol head and FA tails - soluble in fat and water (emulsifiers)
  • Sterols - multiple ring structures - precursor of other substances
  • Energy Source / Reserve; Insulation and Protection, Carrier of Fat-Soluble Compounds; Sensory Qualities
  • Essential = FA with double bonds before the 9th carbon (Omega 3 and 6)
  • Non-essential = FA with no double bonds before the 9th carbon (Omega 9)
  • Plant and Animal Origin
• Anatomical organs involved in lipid digestion

  • Mouth
  • Stomach
  • Small Intestine
  • Large Intestine
• Lipid digestion


  1. sublingual salivary gland release an enzyme → hydrolyze milk fats

  2. fat mixes with acid through churning activity

  3. Gastric secretions hydrolyze small amount of fat

  4. CCK signals the gallbladder to release bile via common bile duct

  5. Bile binds with fat and becomes emulfied

  6. Pancreas release an enzyme through pancreatic duct → pancreatic lipase and intestinal lipase breakdown fats into monoglycerides, glycerol, and fatty acids for absorption

  7. Fat and cholesterol trapped in fiber exit the body as fecal matter
• Enzymes/Hormones involved in lipid digestion

  • Lingual lipase
  • Gastric lipase
  • CCK
  • Bile
  • Pancreatic lipase
  • Intestinal lipase
• Absorption of small lipid molecules

  glycerol, short-chain and medium-chain fatty acids → diffuse easily into the intestinal cells (passive diffusion) absorbed directly into the bloodstream
• Absorption of large lipid molecules

  • monoglycerides, glycerol and long-chain fatty acids →emulsified by bile → micelles → diffuse into intestinal cells (enterocytes) → reassembled into new TG
  • New TG and other lipids (cholesterol and phospholipids) join protein carriers to form lipoprotein → packed into transport vehicles (chylomicrons)
  • Unabsorbed bile salts return to the interior of small intestines for another load of MG and FA
• Absorption site of lipids

  • chylomicrons enter the central lacteal of the villi and are released into the lymphatic system
  • bile salts are absorbed in the ileum and return to the portal vein → liver → recycled and secreted as part of bile (enterohepatic circulation)
• Timing of lipid absorption

  1. 2 hours postprandial, dietary fat appears into the bloodstream. Fat levels peak after 3-5 hours and generally cleared by 10 hours.
• Health effects of excessive lipid intake

  • Obesity
  • Diabetes Mellitus
  • Liver disease
  • Heart Disease and Stroke
  • Cancer
• Protein


  • Central carbon chain with an amino group (NH2) and acid group (COOH), hydrogen, and a side group (unique structure and differentiates one AA from another)
  • Amino acids - (20 common AA -- each one contain different side group) linked through peptide bonds
  • Essential AA - (9 needs to be supplied through diet -- TVPMILLH)
  • Non-essential AA - (11 can be synthesized by the body -- A4CG3PST)
  • Conditionally EAA - Arginine, Cysteine, Glutamine, Glycine, Proline and Tyrosine
  • Sequence and properties of AA determines protein shape
  • Shape determines protein's function
  • Collagen, motor protein, keratin, enzymes, hormones, immune function, fluid balance, acid-base balance, ransfport function, source of energy and glucose
  • Complete Protein - contains all essential AA
  • Incomplete Protein - some essential AA are missing
  • Complementary Protein - Combination of incomplete protein provides sufficient amounts of all essential amino acids
  • Plant (Incomplete Protein) and Animal (Complete Protein)
• Anatomical organs involved in protein digestion

  • Small Intestine
  • Large intestine
  • Liver and Kidneys
• Protein digestion


  1. Enzymes hydrolyze peptides and the cells absorb them

  2. no protein digestion here

  3. Excess or remaining carbon skeletons can be used to make fatty acids or glucose or broken down completely to yield energy

  4. The liver removees amino groups from excess AA and converts amino group to urea for excretion by kidneys
• Enzymes/Hormones involved in protein digestion

  • chymotrypsin (cleaves pep bonds to AA (Phen, Tyr, Tryp, Met, Asp, His) → carboxypeptidases → elastase and collagenese (smaller polypepties and tripeptides) → intestinal tripeptidases (tripeptides to dipeptides)→ intestinal dipeptidases dipeptides to AA) → intestinal aminopeptidases (amino ends of small peptides)
  • Diseases: celiac disease and cystic fibrosis
• Protein absorption


  • Most protein absorption takes place in the cells
  • After they are absorbed, most AA and few absorbed peptides are transported by the portal vein to the liver to be used for protein synthesis, energy needs or conversion to CHO or fat or released into the bloodstream to other cells
  • Some remain in the intestinal cells and are used to synthesize intestinal enzymes and new cells
  • Some amino acids require active transport
  • Similar amino acids share the same active transport system
  • Other amino acids are absorbed by facilitated diffusion (leucine, isoleucine, and valine) → depend on same carrier molecule
  • Amino acids that share the same transport system are absorbed fairly equally (consumption of large amount of 1 particular AA impairs absorption of other AA from your diet because same transport systems are deficient
  • >99% of protein enters the bloodstream as individual AA
  • Peptides are rarely absorbed and undigested whole proteins are also not absorbed
• Absorption site of proteins

  • lining of duodenum and jejunum
  • Small intestine cells → Portal vein → Liver (stored and released for purpose)
• Amino acid pool and protein turnover

  • The AA pool
  • Available AA
  • Constant recycling of protein
  • Draws on AA pool as needed.
  • Indispensable AA missing
  • Indispensable AA unavailable
  • Amino acids as precursors of DNA, RNA, and coenzymes
  • Breakdown of amino acids
  • Body may break its own protein down to supply the missing AA.
  • Protein synthesis halts and partially completed protein used elsewhere in the body.
  • Protein synthesis; produce energy and glucose
  • Approx 300g are synthesized by the body/d; 200g are recycled from AA (reason why we need little protein in our diet)
  • Also used to make neurotransmitters: Chemicals that send signals from nerve cells to other parts of the body
  • Removes nitrogen (amino) group.
  • Amino groups converted to urea for excretion.
• Protein quality


  • High-quality protein
  • Consider the protein digestibility-corrected amino acid score (PDCAAS)
  • Complementary proteins
  • Nitrogen balance
  • Nitrogen intake vs.nitrogen output
  • Nitrogen equilibrium
  • Nitrogen intake = nitrogen output
  • Positive nitrogen balance
  • Nitrogen intake > nitrogen output
  • Negative nitrogen balance
  • Nitrogen intake < nitrogen output
• Health effects of low protein intake

  • Cancer
  • Gout
  • Obesity
  • Heart Disease
  • Strain Kidney Function
  • Mineral Losses
• Health effects of excessive protein intake

  • Kidneys excrete the products of the protein breakdown (esp harmful for DM patients)
  • Diet with ↑ E from protein increases kidney filtration rate in healthy adults
  • Increase fluid intake to dilute the by-products of protein breakdown
  • high protein diet (esp purified proteins) increases calcium excretion → bone mineral losses
  • adequate intake of protein = adequate calcium intake and acid neutralizing F&V
  • High protein foods are often high in fat
  • Large amts of protein and fat in diet can provide ↑ E contributing to obesity
  • high dietary protein alters hormones and body's response (leptin - regulates food intake) → increases risk of obesity
  • high intake of animal protein (meats and processed meats are ↑SFA) increases blood cholesterol and risk of heart disease, stroke and diabetes
  • choose lean red meats, decreasing food intake, avoid processed meats
  • prolonged high intake of red meat and processed meats increases colon cancer risk and mortality
  • diets high in meat and seafood increases the risk of gout (inflammatory arthritis)
• Vitamins


  Chemical substances that perform specific functions in the body
• Fat-soluble vitamins


  Dissolve in fat (vitamins D, E, K, and A, or the "deka/adek" vitamins), stored in body fat, the liver, and other parts of the body, deficiencies generally take longer to develop
• Water-soluble vitamins


  Soluble in water (the B-complex vitamins and vitamin C), with the exception of vitamin B12 the water-soluble vitamins can be stored in the body only in small amounts, deficiency symptoms generally develop within a few weeks to several months after the diet becomes deficient, niacin, vitamin B6, choline, and vitamin C are known to produce ill effects if consumed in excessive amounts
• Phytochemicals


  Act as hormone-inhibiting substances that prevent the initiation of cancer, serve as antioxidants that prevent and repair damage to cells due to oxidation, block or neutralize enzymes that promote the development of cancer and other diseases, modify the absorption, production, or utilization of cholesterol, decrease formation of blood clots