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Carbohydrates
Fats
Protein
Water
Vitamins
Minerals
6 Classes of Nutrients
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Carbohydrates, Fats, Protein
- Organic
- Contain Carbon
- Has calories
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Nutrients
- Come from food
- - Provide energy
- - Provide building blocks
- - Maintain body cells
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Essential
Must be obtained from diet
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Vitamins, Water, & Minerals
- Essential Nutrients
- Don’t contain calories
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Energy-Yielding Nutrients
- Energy measured in kCalories
- - Carbohydrate
- - Fat
- - Protein
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Non Energy-Yielding Nutrients
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Vitamins
- Organic compounds
- Consumed in small quantities
- Assist in body processes
- Vulnerable to destruction
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Minerals
- Inorganic elements
- Consumed in varying quantities
- Structural component- not metabolized, do not yield E
- Indestructible
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Water
- Indispensable and abundant
- Often taken for granted
- Enormous consumption compared to other nutrients
- Participates in many chemical reactions
- Provides environment for many body activities
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Carbohydrates and Protein
Calorie value: 4
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Fat (lipid)
Calorie value: 9
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Vitamins, Minerals, and Water
Calorie value: 0
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Alcohol (not a nutrient)
Calorie value: 7
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Calorie
- A measurement of energy
- Food is measured in kilocalories (kcal)
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Phyto-Chemicals
- Some foods offer beneficial non-nutrients
- Brightly colored pigments
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Anthropometric Data
- Height, weight
- Body Composition
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Body Composition
- Skin fold
- Underwater weighing
- Bioelectrical impedance (low level current)
- DEXA (low level x-ray)
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Biochemical (lab tests)
Blood, urine
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Clinical
- Physical exams
- - Medical history
- - Drug use, SES
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Dietary
- 24 hour recall
- Food record
- Food frequency questionnaire
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Dietary Guidelines for Americans
- Consume a variety of foods within and among basic food groups while staying within energy needs
- Control calorie intake to manage body weight
- Be physically active every day
- Increase daily intake of fruits & vegetables, whole grains, & nonfat or low-fat milk and milk products
- Choose and prepare foods with little salt
- If you drink alcoholic beverages, do so in moderation
- Keep foods safe to eat
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Healthy Diet
To “ consume a variety of foods balanced by a moderate intake of each food”
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Nutrient Density
Comparison of vitamin and mineral content to number of kcals
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Empty Calories
Provides kcals and few to no other nutrients
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Energy Density
Comparison of the kcal content to the weight of the food
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Dietary Reference Intake (DRI)
- Nutrient standards for US and Canada
- Nutrient recommendations to prevent chronic diseases
- NOW considered malnutrition
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Dietary Reference Intake for Fiber
- 38 grams for men (till age 50)
- 25 grams for women (till age 50)
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Dietary Reference Intake Uses
- Diet planning
- Aim for RDA or AI
- Do not exceed the upper limit
- For the health population
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EAR: Estimated Average Requirement
- Population-wide average nutrient requirements
- Intake value to meet the requirement of 50% the healthy individuals in a particular life stage and of a given sex
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Estimated Average Requirement Uses
Caloric needs (to prevent over-nutrition)
- Females- 2000 calories a day
- Males- 3000 calories a day
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RDA: Recommended Daily Allowance
Vitamins and Minerals (to ensure adequate intake)
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UL: Tolerable Upper Level Intake
- Highest level of usual daily nutrient intake likely to pose no risk of adverse health effects
- Helps assess:
- - Supplements
- - Excess amounts of fortified foods
- Not a goal, but a ceiling
- Not enough information to set one for all nutrients
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AMDR: Acceptable Macronutrient Distribution Ranges
- No RDA for Carbohydrate, Protein or Fat, but…
- Ranges of intakes are recommended that are associated with reduced risk of chronic disease
- - Carbohydrates: 45-65% total energy
- - Protein: 10-35% total energy
- - Fat 20-35% total energy
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My Pyramid
- 6 food groups represented by colors
- Choose food in approximate proportion to the base widths of the bands
- Physical activity
- Moderation
- Not for children under age 2
- Each food is deficient in at least one essential nutrient
- Variety is key
- Calorie and nutrient content may vary within a food group
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6 oz every day
1 slice of bread= 1 oz
Grains (My Pyramid)
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2 ½ cups every day
Vegetables (My Pyramid)
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2 cups every day
Fruits (My Pyramid)
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3 cups every day
For children 2-8: 2 cups
Milk (My Pyramid)
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5 ½ oz every day
Piece of meat= deck of cards= 3 oz
Meat and Beans (My Pyramid)
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Diet Planning with the Exchange System
- 7 Major food groups
- Foods are grouped according to calories (energy), carbohydrate, and fat content
- Portion Size
- Foods may be grouped in an “unlikely” place
- - Bacon, peanuts, avocados are in the fat group
- - Cheese is a “high fat” meat
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Starch/Bread
Fruit
Milk (nonfat, low fat, whole)
Other Carbohydrates
Vegetables
Meat (very lean, lean, medium fat, high fat)
Fat
7 Major Food Groups of Exchange System
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Food and the Body
- Taking food into the mouth DOES NOT assure admission to the body
- When food is in G.I. tract, it is OUTSIDE the body
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General Functions of a GI System
- Propulsion and mixing of GI contents
- Secretion of Digestive Juices
- Digestion of food
- Absorption of nutrients
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Digestion
The process by which food is broken down into absorbable units
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Mouth
Digestion begins here (especially carbohydrate digestion)
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Salivary Glands
- Enzymes:
- - Salivary amylase: For carbohydrates
- - Lingual lipase: For fats
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Esophagus
“tube” from mouth to stomach
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Stomach
- Holds food for 2-4 hours, capacity is 4 cups
- Grinds and churns swallowed food, mixing it with acid and enzymes= “chyme”
- Stores food: if you don't have one (e.g. surgery), must eat small frequent meals
- Acid medium kills bacteria and helps absorption of iron, calcium
- Secretes an ‘Intrinsic Factor’ need for vitamin B12 absorption
- Mucus layer prevents autodigestion
- Strongest muscle in intestinal tract
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Small Intestine
- Major site of digestion and absorption
- About 10 feet long
- Divided into: Duodenum, jejunum, ileum
- Once here, chyme inhibits motor activity of stomach
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Emptying into Small Intestine Depends On..
- Fluidity of chyme
- Amount of chyme in the small intestine
- Amount of fat present (slows emptying)
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Large Intestine (Colon)
- Lower part of intestine
- Completes digestion
- Absorbs water and minerals
- Divided into: ascending colon, transverse colon, descending colon, sigmoid colon
- Removes water (chemical aspect)
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Appendix
Narrow blind sac at the beginning of the colon role in immune system: stores lymph cells
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Pancreas
Gland that secretes digestive enzymes and juices into small intestine
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Gall Bladder
Stores bile and secretes bile into small intestine
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Peristalsis
Waves of contractions involving circular and longitudinal muscles throughout GI tract
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Stomach Action
Strongest muscles of GI, turn food into “chyme” (mixture of food and GI juices, very acidic)
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Sphincters
Circular muscles at specific points in GI tract that act as gates to regulate flow
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Saliva
Contains enzymes; especially for carbohydrate digestion
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Gastric Juice
- From stomach, made of enzymes and hydrochloric acid (HCl)
- Especially used for protein digestion
- Mucus protects stomach from HCl
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Pancreatic Juice (Secreted into Intestine)
- Enzymes for carbohydrates, protein, fat
- Bicarbonate to neutralize “chyme” coming from stomach
- Intestinal enzymes:
- - Enzymes for carbohydrates, protein, fat
- - Enzymes work best in neutral pH
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Bile
- Made by the liver, stored in the gall bladder
- Gall bladder squirts it in to Small Intestine when fat is present
- Not an enzyme, but an emulsifier (break fat into little droplets)
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Protective Factors
- Good bacteria + intestinal flora
- Probiotics
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Good bacteria + Intestinal Flora
- Make some vitamins
- Protect against “bad” bacteria, viruses
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Probiotics
Supplements containing “good bacteria”
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Big Unit -> Little Unit
- Protein -> amino acids*
- Carbohydrates -> monosaccharide*
- Fat -> fatty acids* and glycerol*
- *These cross the intestinal cell into the bloodstream
- - They are absorbed
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Anatomy of the Absorptive System
- Surface of small intestine covered with “villi"
- Villi (and microvilli) increase surface area that of a tennis court!
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Villi
Finger-like projections
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Intestinal Cells
- Villi and microvilli contain enzymes and “pumps”
- Specialized: Different nutrients are absorbed in different areas of the small intestine
- Contains a blood supply and lymph
- Nutrient transport
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Nutrient Transport of Intestinal Cells
Goes to bloodstream or lymphatic system
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Bloodstream
- Water soluble nutrients -> go here
- Monosaccharide’s, amino acids, small fats, minerals, water soluble vitamins (= B vitamins and Vitamin C)
- Go first to liver via portal vein
- Liver is the major metabolic organ of the body
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Lymphatic System
- Fat soluble nutrients -> go here
- Larger fats and fat-soluble vitamins (Vitamin A, E, D, K)
- Does not go to liver first, but empties into blood near heart
- Lymph is similar to blood, but no red cells or ‘pump’
- Lymph squeezed by muscles to circulate in contents
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Simple Diffusion
Water and small lipids
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Facilitated Diffusion
Water-soluble vitamins (B & C)
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Active Transport
Glucose and Amino acids
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Myth of "Food Combining"
- It is a myth that can’t eat certain food combinations
- Food can help each other be absorbed
- Example: Vitamin C helps iron absorption
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Large Intestine Digestion
- Nutrient digestion already complete
- Some digestion of fiber by bacteria
- Fiber has NO calories
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Large Intestine Absorption
- Water
- Sodium, potassium, chloride
- Vitamin K (produced by bacteria)
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Large Intestine Elimination
Get rid of what we don’t use
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Gastro-Esophageal Reflux Disease
- Stomach contents re-enter esophagus
- Treatment:
- - Small meals
- - No food 3 hours before bed
- - Elevate head of bed
- - Use antacids
- Choking
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Celiac Disease
- Gluten-sensitive enteropathy
- Allergic to gluten
- - Antibodies attack microvilli -> GI inflammation
- Managed by gluten-free diet
- - No wheat, rye, barley
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Irritable Bowel Syndrome
- Affects 20% of Americans
- Cramps, gassiness, bloating, irregular bowel function
- Treatment
- - Elimination diet: Meat and Starches
- - Moderate caffeine
- - Low fat, small meals
- - Stress reduction
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What's on a Food Label
- Product name
- Company’s name and address
- Ingredients in descending order by weight
- Amount in the product
- Product bar code
- *Nutrition facts panel*
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The Daily Values
- Daily goals of a person consuming 2000 kilocalories
- Helps consumers tell whether or not a food has a lot or little of a nutrient
- Makes it easier to compare brands
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Descriptive Terms for Food Labeling
- If less than 2 milligrams of cholesterol and 2 milligrams or less of saturated fat, then can say “cholesterol free”
- If raw and never been frozen, can say “fresh”
- Health claims
- - FDA approves statement linking diet and health
- - The nutrient or food substance must be related to a disease or health condition for which most people or a specific group of people, such as the elderly, are at risk
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Carbohydrates
- Populations of the world derive more than ½ of their nutrients from these types of foods
- Easy to grow
- Highly palatable
- Can be stored for reasonable periods
- Classic examples: rice, corn, wheat, potatoes, oats
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Simple Carbohydrates (sugars)
Complex Carbohydrates (starches and fiber)
2 Main Carbohydrates in Food
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Simple Carbohydrates
- Monosaccharides
- Disaccharides
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Monosaccharides
- Glucose
- Fructose
- Galactose
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Glucose
- Found in fruits, vegetables, honey
- “Blood sugar” – used for energy, essential
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Fructose
- “Fruit sugar”
- Found in fruits, honey, corn syrup
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Galactose
Found as part of lactose in milk
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Complex Carbohydrates
Polysaccharides
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Polysaccharides
- Starch
- Glycogen
- Dietary Fiber
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Starch
- Long chains of glucose units
- Amylose
- Amylopectin
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Amylopectin
Branched chains
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Glycogen
- Body makes this
- Highly branched chains of glucose units
- Body’s storage form of carbohydrate in muscles and liver
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Dietary Fiber
- Can’t digest (get 0 calories from this – if you can’t digest a food, the food doesn’t get into your blood stream, therefore you don’t gain calories)
- Chains of monosaccharides
- - Short chains
- - Long chains
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Soluble Fiber
- Found in oats, legumes (dried peas and beans)
- Lowers blood cholesterol
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Insoluble Fiber
- Found in grains, vegetables
- Increases GI transit (moves food through GI faster)
- - Prevents constipation
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Carbohydrate Digestion
- End products of this digestion:
- Monosaccharides: glucose, fructose, galactose
- - Absorbed into bloodstream
- Fibers are not digested (zero calories), excreted in feces
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Carbohydrate Intake
- 45-65% of kilocalories
- Daily value (for 2,000 kcal) = 300 grams
- Dietary guidelines
- - Moderate sugar intake
- - Variety of grains, fruits, and vegetables
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High Sugar Intake
- Low nutrient content
- Contributes to tooth decay
- If excess kcal, contributes to obesity
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High Fiber Intake
- Better control of blood glucose
- Reduced risk of heart disease
- Healthier GI functioning
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Sugar
- As an additive, this may...
- Enhance flavor
- Provide fuel for fermentation (bread, beer, wine)
- Act as a preservative (jams)
- Balances acidity of tomato and vinegar-based products
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Lactase
enzyme that digests disaccharide lactose
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Lactose Intolerance
- Symptoms: bloating, gas, diarrhea
- Causes: lactase deficiency or decreased lactase activity, or damage of intestinal villi by disease
- Prevalence
Only 30% of adults worldwide can digest lactose thru out their lifespan
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Dietary Changes for Lactose Intolerance
- Low lactose dairy products, e.g. aged cheese and yogurt are ok
- Must limit milk, ice cream
- Can use Lactaid milk, lactase pills
- Other calcium sources: Ca-fortified orange juice, soymilk, canned sardines or salmon with bones
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Glycemic Index
- Classifies foods based on their potential to raise blood glucose levels
- Expressed as a percentage of the response of glucose (glucose = 100%)
- High glycemic index foods trigger sharp rise in blood glucose
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Glycemic Index is Infected by:
- Type of carbohydrate
- Cooking process
- Presence of fat or fiber
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Triglycerides
1 glycerol + 3 fatty acids
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Saturated Fats
- No double bonds
- Solid at room temperature
- Usually of animal origin
- Food sources: butter, lard
- Exceptions: Coconut oil, palm oil
- - From plants
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Monounsaturated Fats
- One double bond
- Liquid at room temperature, but will become solid if refrigerated
- Food sources: olive oil, canola oil, peanut oil, sesame oil
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Polyunsaturated Fats
- 2 or more double bonds
- Liquid at room temperature or refrigerator temperature
- Usually of plant origin
- Food source: corn oil, safflower oil
- Omega-3
- Omega-6
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Omega-6
- Found in vegetable oils and meats
- Serve as raw material for the production of eicosanoids in the body
- EFA deficiency symptoms
- - Growth retardation, reproductive failure, nerve problems
- - Uncommon, but if have chronic disease, may become deficient
- - Most common form of fat in food and in body
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Phospholipids
- Similar to Triglyceride
- Contains phosphate and nitrogen
- Lecithin (not an essential nutrient)
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Function of Phospholipids
- Constituent of cell membranes
- Emulsifying agent- helps fat and water mix- also used in food industry
- Contain nitrogen and phosphorous
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Sterols
Composed of multiple ring structures
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Function of Sterols
- They are the starting material for:
- Cholesterol (endogenous)
- Bile acids
- Sex hormones (estrogen, testosterone)
- Adrenal hormones (cortisol)
- Vitamin D
- Cholesterol can be converted to all of the above
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Dietary Source of Sterols
- Cholesterol is one that is found in foods of ANIMAL ORIGIN
- Only meat, eggs, dairy, shellfish, fish
- Eggs and shrimp have highest cholesterol
Maximum intake a day is 300 mg
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Lipid Digestion
- Most of the digestion takes place in the Small Intestine
- First must be “emulsified” by bile
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Facts about Bile
- Made from cholesterol
- Can either be reabsorbed and reused OR
- Can be trapped by soluble fiber (oats) in the intestine and then excreted
- If excreted, then more cholesterol must be used to make more bile
- Liver uses blood cholesterol to make this
- Nothing is stored in the liver
- Stored in gall bladder
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Absorption and Transportation of Lipids
- Small fats (water soluble) -> blood -> liver
- Larger fats (non-water soluble) -> packaged into chylomicrons -> lymph system -> blood
- Chylomicrons contain TG, cholesterol, phospholipids
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Lipid Transport through the Blood
They are transported as Lipoproteins (transport vehicle= clusters of lipids with protein around it)
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Types of Lipoproteins in Blood
- Chylomicrons
- Very Low Density Lipoproteins (VLDL)
- Low Density Lipoproteins (LDL)
- High Density Lipoproteins (HDL)
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Low Density Lipoproteins
- “Bad Cholesterol"
- LDL gives up cholesterol to cells
- Less healthy
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High Density Lipoproteins
- “Good cholesterol”
- Transports cholesterol back to liver from the cells (body tissues) for disposal
- Healthy
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Cardiovascular Disease
- Elevated (total) blood cholesterol is major risk factor
- Dietary saturated fatty acids raise blood cholesterol more than dietary cholesterol does
- Raises LDL and lowers HDL
- Some research suggests..
- - Polyunsaturated fats lower LDL
- - Monounsaturated fats raise HDL
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Omega-3 Fatty Acids
- Diets high in fish oils
- Lowers blood cholesterol and reduces risk of Cardiovascular Disease
- It is recommended that fish be consumed at least once/week
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To Improve LDL/HDL Ratio
- Weight control
- Mono- and Polyunsaturated fats in diet
- Soluble fibers (oat bran)
- Antioxidants (vitamin C, vitamin E)
- Moderate alcohol consumption
- Exercise
- Being female
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Cancer and Lipids
High dietary fat (saturated fat) may increase in some cancers (breast, prostate)
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Obesity and Lipids
Dietary fat is easily converted (90% efficient) to body fat
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Hydrogenation
- Hydrogen gas is mixed with a liquid fat (oil)
- Causes fatty acids to be more saturated and thus more solid
- Hydrogenated corn oil- margarine
- Also causes formation of trans fats
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Trans-Fatty Acids
- Can form during hydrogenation
- Very common in:
- - Margarine
- - Baked products
- - Snack chips/crackers
- Are unhealthy because they may increase heart disease
- Very difficult for the body to metabolize, so they can build up in the body
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Olestra Pros
- No cholesterol
- 0 calories
- Body does not recognize it as a fat
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Olestra Cons
- Upset stomach
- Won’t be broken down in liver
- Loss of vitamins
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Fats in Diet
- Added Fats
- Meat, poultry, fish, eggs, and nuts
- Milk, yogurt, cheese
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Recommended Intakes of Fat
- Reduce total fat intake
- - 20-5% of less of kilocalorie; but don’t go less than 15% of kilocalorie
- Reduce saturated fat intake
- - <10% of kilocalories
- Reduce cholesterol intake
- <300 mg/day
- Select lean meats and nonfat milks
- Eat plenty of vegetables, fruits, and grains
- Use fats and oils sparingly
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