Normal Absorption & Digestion Study Guide

Dietary Reference Intake (DRI)

• Reference values used to guide nutrient intake in healthy people for both macro- and micronutrients

• Sorted by age, sex, pregnancy & breastfeeding status

Recommended Dietary Allowance (RDA)

• Average daily intake sufficient to meet the needs of 97-98% of all healthy people

• Vary by age, sex, pregnancy and breastfeeding status

Adequate Intake (AI)

• Used when there is insufficient data to set RDA

• Set at level assumed to ensure nutritional adequacy (EAR to UL)

Tolerable Upper Intake Level (UL)

• Maximum daily intake that is unlikely to cause adverse health effects (i.e. toxicity)

• Set at conservative and safe level

Estimated Average Requirement (EAR)

• Nutrient intake level estimated to meet the needs of 50% of people in sex and age group

• Used to determine RDA

Acceptable Macronutrient Distribution Range (AMDR)

used to report macronutrient recommendations

Carbohydrate AMDR

45-65% of daily kcal

Protein AMDR

10-35% of daily kcal

Fat AMDR

20-35% of daily kcal

Carbohydrate Function

• Major source of energy

• Preferred energy source for brain

• Involved in cellular communication (glycoproteins)

• In plants structural role (cellulose)

Carbohydrate Kcal

4 kcal/g

Fiber DRI

14 g/1000 kcal or > 25 g/day for adults

Monosaccharides

Glucose, Fructose, Galactose

Disaccharides

Maltose, Sucrose, Lactose

Polysaccharide Examples

Amylose, amylopectin, glycogen, cellulose

Maltose

• Glucose + Glucose

• Broken down by maltase

Sucrose

• Fructose + Glucose

• Broken down by sucrase

Lactose

• Galactose + Glucose

• Broken down by lactase

Glucose Storage

• Glycogen in muscles and liver

• Only liver can convert glycogen back to glucose

Polysaccharides

• long chains of glucose

• Shape determined by number and type of glycosidic bonds

• Properties and digestibility determined by shape

Cellulose

Insoluble fiber, indigestible due to B glycosidic bonds

Protein Function

• Enzymes

• Build muscles and other tissues

• Structural support

• Transporters (e.g. hemoglobin)

• Receptors

• Muscle contraction

• Regulate gene expression

• Immune function

• Fluid balance

• Hair, skin, and nails

Protein to Polypeptides

Via Pepsin & Gastric Acid

Polypeptides to Oligopeptides & Free Amino Acids

Via Pancreatic Enzymes

Oligopeptides to Free Amino Acids

Brush Border Enzymes

Essential Amino Acids

Must come from diet, cannot be made in body

Essential Amino Acid List

PVT TIM HiLL

• Phenylalanine

• Valine

• Tryptophan

• Threonine

• Isoleucine

• Methionine

• Histidine

• Leucine

• Lysine

Conditionally Essential Amino Acids

Essential in some physiological states (infant prematurity, PKU, severe catabolic disease)

Conditionally Essential Amino Acids List

GAG PAST

• Glycine

• Asparagine

• Glutamate

• Proline

• Arginine

• Serine

• Tyrosine

Non-Essential Amino Acids List

ACAG

• Alanine

• Cysteine

• Aspartate

• Glutamate

Protein Complementation

Combining two different plant proteins to ensure intake of all nine essential acids

• Doesn’t need to be eaten at the same meal; a varied diet is effective to meet protein needs

• Inherent in many cultural dishes (e.g. rice and beans)

Limiting Amino Acids

• Low in plant foods

• Focus of protein complementation

Methionine

• Limiting AA in legumes and vegetables

• Found in grains, nuts, and seeds

Grains Limiting AA

Threonine and Lysine (found in legumes)

Nuts & Seeds Limiting AA

Lysine (found in legumes)

Corn Limiting AA

Tryptophan & Lysine (found in AA)

Protein Structure

• Backbone with carboxyl group and amino group

• Amino group provides nitrogen and impacts molecule properties (size, polarity, acid/base properties)

Protein Primary Structure

• Sequence of amino acids

• Peptide and disulfide bonds

Secondary Protein Structure

• Spatial structure

• Hydrogen bonds form helix or pleated sheets

Tertiary Protein Structure

• 3-dimensional structure

• Disulfide bonds, salt bridges, hydrogen bonds, non-polar hydrophobic reactions

Quarternary Protein Structure

• Multiple sub-units

• Hydrogen bonds, ionic interactions, hydrophobic interactions

Denaturing Proteins

Disruptions in protein structure by heat (cooking) or precipitation (by acids/bases, detergents, heavy metals)

Simple Proteins

only amino acids (e.g. albumin)

Conjugate Proteins

Amino acids and other compounds (e.g. lipoproteins, LDL)

Protein Storage

Liver amino acid pool (1% body protein)

• Constant flow of amino acids in and out

• Estimated that body breaks down and builds 250 g protein daily

When liver pool is insufficient, body will pull from elsewhere (e.g. skeletal muscle)

Protein Waste

Nitrogen removed when amino acids are used and converted into urea

Urea

• Safe and highly water soluble

• Excreted in urine

Protein as Energy

Not primary function; only done in times of need though converting into glucose or ketone bodies

Glucogenic Protein

May be converted into glucose

Ketogenic Proteins

May be converted into ketogenic bodies

• Lysine

• Leucine

Ketogenic & Glucogenic Amino Acids

• Phenylalanine

• Isoleucine

• Threonine

• Tryptophan

• Tyrosine

Fat Functions

• Store excess energy

• Make cell membranes

• Transport fat soluble vitamins

• Hormone production

Saturated Fat DRI

< 10% daily kcal

Linoleic Acid DRI

12-17 g/day

Linolenic Acid DRI

1.1-1.6 g/day

Fat Digested By

Lipase

Triglyceride —> Diglyceride —> Free Fatty Acids & Monoglyceride

Triglyceride Structure

Glycerol Backbone + 3 Fatty Acids (may be different fatty acids)

Fatty Acid Structure

Made of carbon & hydrogen atoms

Saturated Fatty Acids

• All single bonds

• Solid at room temperature

Unsaturated Fatty Acids

• Double bonds

• Liquid at room temperature

Cis Bonds on Fatty Acids

• Hydrogen on same sides

• More bent shape

Trans Bonds on Fatty Acids

• Hydrogen on opposite sides

• Straighter shape

• Act more like saturated fats

Monounsaturated Fatty Acids

One double bond

Polyunsaturated Fatty Acids

Multiple double bonds

Phospholipids

Two fatty acids and a phosphate group

• Hydrophobic and hydrophilic ends are excellent for single and double layer membranes

Omega Naming

Location of first double bond from methyl group (CH3) Omega end

Saturated Fat Food Sources

• Coconut oil

• Palm oil

• Cottonseed Oil

• Butter

• Beef Tallow

• Lard

Low in Saturated Fat

• Canola oil

• Safflower oil

• Sunflower oil

• Peanut oil

• Corn oil

• Olive oil

• Soybean oil

Linoleic Acid (Omega-6) Food Sources

• Safflower oil

• Sunflower oil

• Cottonseed oil

• Corn oil

• Soybean oil

A-Linolenic Acid (ALA) (Omega-3) Food Sources

• Canola oil

• Soybean oil

• Flaxseed

• Walnuts

Omega-3 Categories

• A-Linolenic Acid (ALA)

• Eicosapentanoic Acid (EPA)

• Docosahexaenoic Acid (DHA)

Eicosapentanoic Acid (EPA) (Omega 3) Food Sources

• Marine algae

• Fish oils

• Shellfish

Docosahexaenoic Acid (DHA) (Omega 3) Food Sources

• Animal fat

• Fish oils

• Shellfish

Omega-3 Function

• Key role in vision development and brain development

• Recommended to supplement in pregnancy

Omega-6 Categories

• Linoleic Acid (LA)

• Arachidonic Acid (AA)

Linoleic Acid (LA) (Omega-6) Food Sources

• Corn oil

• Safflower oil

• Cottonseed oil

• Sunflower oil

• Soybean oil

• Peanut oil

Arachidonic Acid (AA) (Omega-6) Food Sources

Small amounts in meat and eggs

Omega-6 Deficiency

• Eczema, poor growth, petechiae

• Seen in TPN patients who are not receiving sufficient lipid infusion

Alcohol Kcal

7 kcal/g

Alcohol (Non-Nutritive Nutrient)

• Provides kcal without nutrients

• May displace consumption of nutrients

• Damage to liver and GI tract can lead to malabsorption and malnutrition

Thiamine Deficiency in AUD Mechanisms

• ETOH use inflames stomach lining and GI tract impairing ability to absorb nutrients

• Inadequate vitamin intake

• Reduced hepatic vitamin storage

• Possibly decreased conversion to active form of vitamin

Thiamine Deficiency

• Rare in developed countries

• Common among those with AUD

  • 80% of those addicted to alcohol

Phytochemicals

Chemicals produced by plants

• give fruits and vegetables their bright colors and health benefits

• Some thought to be health promoting or protective against chronic disease and may be sold as supplements

Phytochemical Classes

• Flavonoids

• Carotenoids

• Phytosterols

• Isothiocyanates

• Terpenes

• Organosulphides

• Saponins

• Phenolic acids

• Lignans

• Glucosinolates

Flavonol Sources

• Onions

• Kale

• Tomatoes

• Endives

• Pears

• Tea

• Green Tea

• Leafy Lettuce

• Apples

• Ginkgo Biloba

• Wine

• Olives

• Cranberries

• Turnip Greens

Flavones Sources

Parsely and some cereal grains

Flavanones Sources

Citrus fruits

Isoflavones

• Legumes

• Milk

• Cheese

• Nuts

• Flour

• Soy Sauce

• Tofu

• Miso

Anthocyanids Sources

• Berries

• Cherries

• Plums

• Red Wine

Flavonoids

give red color and act as antioxidants

Lignan Sources

• Berries

• Flaxseed

• Nuts

• Rye Bran

Phytosterols Sources

Vegetable Oils (soy, canola, corn, sunflower)

Isothiocyanates & Glucosinolates Sources

Cruciferous vegetables (broccoli, cabbage, Brussels sprouts, mustard, watercress)

Phenolic Acid Sources

• Blueberries

• Strawberries

• Raspberries

• Cherries

• Pears

• Echinacea

• Grape Juice

• Apples

• Oranges

• Grapefruit

• White Potato

• Coffee Bean

• St. John’s Wort

Organosulphides Sources

• Garlic

• Onion

• Leeks

  • Cruciferous Vegetables

Carotenoids

Lycopene, Lutein, Beta-Carotene, Alpha-Carotene

Carotenoid Sources

• Tomato

• Pumpkin

• Guava

• Squash

• Carrot

• Watermelon

• Papaya

Terpene Sources

• Citrus

• Cherries

• Ginkgo Biloba

Saponins Sources

• Alfalfa sprouts

• Potato

• Tomato

• Ginseng

Antioxidants

• Functional class of molecules

• “Give” electrons to free radicals to neutralize negative effects

• Role in DNA repair (hypothesize to prevent cancer but may interfere in cancer treatments)

• Supplementation hasn’t shown promise in research