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HNSC 1210 > Lipids > Flashcards

Lipids Flashcards

1
Q

Lipids

A

Soluble in organic solvents but not in water (and our body is mostly water)

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2
Q

Recommendations for Dietary Fat

A
  • Polyunsaturated fatty acids - DRI:
    ◦ 5-10% energy from linoleic acid (omega 6)
    ◦ 0.6-1.2% energy from linolenic acid (omega 3)
    Cholesterol:
    ◦ DRI: minimize intake within context of healthy diet
    ◦ Only about 1/3 population responds to lowering dietary cholesterol
    intake
    ◦ Limit eggs, shellfish, liver, etc. but these are also nutritious foods
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3
Q

Classification of Lipids (1)

A
  • Triglycerides
    • 95% of lipid in foods and body fat
    • 3 fatty acids + glycerol backbone
    • Glycerol is made from glucose or amino acids
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4
Q

Classification of Lipids (2)

A
  • Fatty acids classified by chain length
    • Short: < 10 carbons
    • Medium: 12-14 carbons
    • Long: > 16 carbons
  • Shorter chain FAs tend to be softer and melt more readily at room temperature
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5
Q

Classification of Lipids (3)

A
  • Fatty acids classified by degree of saturation
    • Saturated: no double
      bonds
      • Tend to be solid at room temp.
      • Ex: butterfat, coconut &
        palm oils
  • Monounsaturated: 1 double bond
    • Ex: canola & olive oils
  • Polyunsaturated: 2+ double bonds
    • Tend to be liquid (oils) at room temp.
    • Ex: plant & fish oils
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6
Q

Effects of processing on Saturated Fats

A
  • Margarines
    • Hydrogenation: removing C=C double bonds by adding
      hydrogen
      • Vegetable oil → “hard” margarine, hydrogenated shortening)
      • Better storage/less rancidity and high smoke point for frying
      • Creates trans-fatty acid which act like saturated fatty acids in the body
        (increases risk of cardiovascular disease)
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7
Q

More on Margarines

A
  • Trans fatty acids
    • Food labels require a separate category
    • 2018: Health Canada banned partially hydrogenated oil in
      foods
  • Blending different oils to produce a “soft margarine”
    • E.g., Becel and other non-hydrogenated products
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8
Q

Other lipids (1)

A
  • Phospholipids
    • Glycerol backbone + 2 fatty acids + phosphorus containing molecule
    • Water and fat soluble
    • Can serve as emulsifier
    • E.g., lecithin in egg yolk – no special health promoting
      abilities
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9
Q

Other Lipids (2)

A
  • Sterols
    • Cholesterol: present in cell membranes and bile
      • Precursor for vitamin D, sex hormones (estrogen, testosterone), stress hormones (epinephrine)
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10
Q

Lipid Digestion (1 Stomach)

A
  • In the stomach:
    • Fat separates from watery components and floats to top
    • Little fat digestion
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11
Q

Lipid Digestion (2 Small Intestine)

A
  • In the small intestine:
    • Bile needed to emulsify lipid and chyme
    • Pancreatic lipase (enzyme) to split into smaller particles
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12
Q

Lipid Absorption

A
  • Small lipids (short and medium chain FAs and glycerol) enter capillary network → bloodstream
  • Large lipids (long chain FAs and monoglycerides [glycerol+1 fatty acid ]) travel in bloodstream as
    chylomicrons
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13
Q

Lipid Transport

A
  • Lipoproteins
    • Chylomicrons: dietary lipid and carrier proteins  transport fats through watery blood fluids
    • Very low density lipoprotein (VLDL): transport triglycerides and lipids synthesized in liver body cells
    • Low density lipoprotein (LDL): transports lipids and cholesterol body cells
      (muscle, fat)
    • High density lipoprotein (HDL): return cholesterol in body cells liver for excretion
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14
Q

Lipid Metabolism

A
  • When body starts to run out of fuel from food, turns to body stores
  • FAs are used for energy by many organs: typical fuel mix is 50/50
    carbohydrate/lipid for liver and muscle (at rest)
  • Any time fat broken down for energy, CHO must be available
    • Otherwise, ketones develop (products of incomplete fat breakdown) and build up in blood and urine
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15
Q

Blood Cholesterol & Cardiovascular Disease
Risk

A
  • High LDL-cholesterol increases risk for heart disease
  • Major risk factors for heart disease:
    • High LDL cholesterol
    • Low HDL cholesterol
    • A diet high in saturated and trans fats, and low in vegetables, fruits, and
      whole grains
  • Diet (low fat & antioxidant nutrients) and lifestyle factors important
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16
Q

Cholesterol

A
  • Cholesterol has precursor and structural roles; required for health
  • 75-80% is synthesized de novo (in the body)
    • Drugs to inhibit synthesis
  • Stimulation of synthesis by saturated fats
  • Dietary cholesterol plays a lesser role than saturated and trans fat in cardiovascular disease
  • ~60% exhibit little increase in blood cholesterol with high cholesterol diet
17
Q

Essential Fatty Acids
(EFAs)

A
  • Linoleic acid (omega-6) and Linolenic acid (omega-3)
    • The only fatty acids that cannot be synthesized by the body
    • Essential nutrients
    • Polyunsaturated fatty acids
    • Used by the body to make eicosanoids
    • Biologically active compounds that regulate body functions
18
Q

EFAs

A
  • When diet deficient in all polyunsaturated fatty acids (PUFAs):
    • Skin lesions
    • Reproductive failure
    • Fatty liver
    • Kidney disorders
    • Reduced learning
    • Impaired growth
    • Impaired vision
  • Deficiency rare: body stores some extra
19
Q

Omega-6

A
  • C = C 6 carbons from end
  • Ex: Linoleic acid
  • DRI: 5-10% energy from n-6 fatty acids
  • Sources: vegetable oils, seeds, nuts, whole grain products
20
Q

Omega-3 (1)

A
  • C = C 3 carbons from end
  • Ex. Linolenic acid
  • DRI: 0.6-1.2% energy from n-3 fatty acids
  • Sources: flaxseed, flaxseed oil, canola oil, fish (especially deep sea fish)
21
Q

Omega-3 (2)

A
  • N.B. ratio of n-6/n-3: need more n-3 in our diet (like
    ancestors) to prevent heart disease
  • Recommendation: 2-3 meals of fatty fish per week to improve heart health
  • EPA/DHA content reduced in fried fish
  • Studies: fish more beneficial than supplements
22
Q

Potential Benefits of EPA/DHA

A
  • Heart disease (supported by most studies)
  • Mental health and cognition
  • Cancer (research promising, but need further evidence)
23
Q

Weighing Seafood’s Risks and Benefits (1)

A
  • Mercury contaminated fish
    • Generally low levels of mercury contaminate most fish species
    • It is yet to be established just how much mercury worsens preexisting heart disease
  • Fish heavily contaminated with mercury
    • Shark
    • Swordfish
    • King mackerel
    • Fresh tuna steak (Albacore)
    • Tilefish
24
Q

Weighing Seafood’s Risks and Benefits (2)

A
  • Fish/seafood lower in mercury
    • Shrimp
    • Canned light tuna (canned albacore [“white”] tuna contains more
      mercury than light tuna)
    • Salmon
    • Pollock
    • Catfish
25
Q

Weighing Seafood’s Risks and Benefits (3)

A
  • Recommendations
    • Consume a variety of fish
      • Minimizes exposure to any particular toxin that may accumulate in a
        particular fish species
  • Pregnant individuals and children
    • Most sensitive to the side effects of mercury
    • Can safely benefit from safer fish varieties within recommended limits
26
Q

Major Dietary Sources of Fat

A
  • Dairy products (excluding
    milk & butter)
  • Processed meat
  • Margarine
  • Salad and cooking oils
  • Bakery products
  • Fresh meats
  • Butter
  • Fluid milk
  • *All except salad and
    cooking oils are sources of
    saturated fat
27
Q

Dietary Fat: g, %
Calories

A
  • Ice cream (1 cup=357 Cal) 24 g, 61%
  • Ice milk (1 cup=182 Cal) 6 g, 30%
  • Cheddar cheese (50 g=205 Cal) 16 g, 70%
  • Low fat mozzarella (50 g=142 Cal) 9 g, 57%
  • Wiener for hot dog (2=360 Cal) 32 g, 80%
  • Lean beef (4 oz=250 Cal) 11 g, 40%
  • Macaroni & cheese (1 c=430 Cal) 22 g, 46%
  • Spaghetti & tomato sauce (1c=260 Cal) 9 g, 31%
28
Q

Food Feature: Defensive Dining

A
  • Substitutes for
    high-fat ingredients
  • Fast Food Choices
  • Saturated Fat
    Replacements
  • Choosing Unsaturated Fats Instead of Saturated Fats
29
Q

Fat Replacers

A
  • Fat replacers and artificial fats
  • Alter preparation method, for example:
    • Add water or whip air into foods
    • Add non-fat milk to creamy foods
    • Use lean products vs. high fat
    • Bake rather than fry
30
Q

Controversy 5: Is butter back? The Lipid Guidelines Debate (1)

A
  • Lots of consumer advice in the public media
  • Often controversial
  • Goals: prevention of cardiovascular diseases
  • Role of saturated fats discussed
  • Strong scientific evidence for diet low in saturated fat
31
Q

Controversy 5: Is butter back? The Lipid Guidelines Debate (2 Historic Guidelines)

A
  • Cut total fat intake for cardiovascular disease prevention
  • However, replacement of fats with sugars lead to negative health outcome
  • E.g., increased diabetes and CVD
  • Guidelines evolved with new evidence
32
Q

Controversy 5: Is butter back? The Lipid Guidelines Debate (3 Milestone Research)

A
  • Seven Countries Study of healthy people
    • Death rates from heart disease strongly associated with diets high in saturated fats
    • Death rates from heart disease were weakly associated with diets high in total fat
    • Finland and Crete were the two countries with the
      highest fat intake
      • Finland had the highest rate of death from heart
        disease
      • Crete had the lowest rate of death from heart disease
    • Relative to Finland, people in Crete had a diet
      • High in olive oil
      • Low in saturated fat (<10% of calories)
33
Q

Controversy 5: Is butter back? The Lipid Guidelines Debate (4 Present Guidelines)

A
  • Replace saturated fats with unsaturated fats
  • Specifically polyunsaturated fats are effective
  • Avoid trans-fats
  • When replacing saturated fats with polyunsaturated:
    • Every 1% reduction in calories from saturated fatty acids → leads to → 2 to 3% reduction in CVD
34
Q

Controversy 5: Is butter back? The Lipid Guidelines Debate (5 Health Canada Approved Health Claim)

A

Rplacing saturated fats with polyunsaturated and monounsaturated fats (from vegetable oils) helps lower/reduce cholesterol

35
Q

Controversy 5: Is butter back? The Lipid Guidelines Debate (6 There is debate)

A
  • Biological mechanism underling the beneficial
    effects are unknown
  • Role of the genetic background unknown
  • Actions of specific FAs undetermined
  • Some saturated fats might not be detrimental
  • Oversupply of some polyunsaturated fats might
    be detrimental
36
Q

Controversy 5: Is butter back? The Lipid Guidelines Debate (7 Controversy on Butter)

A
  • Meta-analysis failed to correlate dietary saturated fat intake with the prevention of CVD
  • This meta-analysis was heavily criticized
  • Design limitations became apparent
37
Q

Controversy 5: Is butter back? The Lipid Guidelines Debate (8 What is right?)

A
  • We cannot eat counting individual FA species
  • Beneficial “Portfolio diets” emerged:
    • A health vegetarian diet
    • A healthy American (Canadian?) style diet
    • The classic Mediterranean diet

HNSC 1210 (6 decks)

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