Lipids

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Lipids

• FAT

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Lipid Family

• triglycerides
• fats
• oils
• predominate in food and in the body
• phospholipids
• sterols
• cholesterol

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Lipids

• energy storage
• a lot of calories in a small space
• generally insoluble in water
• stored in special ways in the body
• also function as structural components of cells

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Fatty Acids
fatty acids

• made up of carbon, hydrogen, oxygen
• more carbon and hydrogen so they supply more
  energy/gram
• common building block for most lipids

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• the determining factor in whether to call a fatty
  acid saturated, unsaturated, monounsaturated,
  polyunsaturated, or trans fatty is determined by
  its chemical bonds and structure

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Triglycerides

• the form of lipid most found in food
• 3 fatty acids glycerol
• major class of dietary lipid
• flabby stuff most of us have is cells filled with
  triglycerides

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Degree of Unsaturation

• influences the firmness of fat
• general impression in regards to food
• liquid at room temp unsaturated
• solid at room temp saturated (animal fats)
• shorter the carbon chain, softer the fat at room
  temperature

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• stability
• when exposed to oxygen, fat becomes rancid
  (oxidation)
• saturated fats are more resistant
• protection from oxidation
• sealed, non-metallic, protected from light,
  refrigerated
• addition of antioxidants
• saturate by adding hydrogen molecules
  (hydrogenated)

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Hydrogenation

• also makes oils more manageable at room temp
  peanut butter, hydrogenated vegetable oil

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Trans-Fatty Acids

• hydrogenated fatty acids
• more saturated than natural vegetable oils
• able to pack together more tightly
• more solid are room temperature
• behave more like saturated fatty acids
• hidden in the reporting levels for unsaturated
  fatty acids

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Phospholipids

• minor portion of lipids in diet
• lecithin is most common
• found in eggs, liver, soy, peanuts
• important role in cell membranes
• lecithin is made in liver
• not an essential nutrient

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Sterols

• important players bile, sex hormones, Vit D
• cholesterol is starting material
• cholesterol
• only found in food derived from animals
• good or bad cholesterol in not a type of
  cholesterol found in food
• refers to the transportation of cholesterol in
  the blood
• made in liver from carbs, protein, fat
• 800-1500 milligrams/day

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Lipid Digestion

• mouth
• slow start
• some hard fats begin to melt
• stomach
• churning mixes chyme and breaks up fat into
  smaller droplets
• expose fat to enzymes
• little fat digestion actually takes place

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• small intestine
• gall bladder releases bile
• acts as an emulsifier
• brings fats into water solution found in
  intestine
• fully digested when enzyme lipase is encountered
• once bile has completed its task
• reabsorbed from intestine and recycled
• trapped by fibers in large intestine and
  eliminated
• reduces blood cholesterol

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Lipid Absorption

• small triglycerides can diffuse into intestinal
  cells, then absorbed into blood
• larger long chain fatty acids merge in micelles
  (emulsified fat droplets)
• allows for solubility in digestive fluids and
  movement to the intestinal cells
• once inside cells, reassembly takes place into
  new triglycerides

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Absorption of Fat
Small intestine
Stomach
Monoglyceride
Short-chain fatty acids
Medium-chain fatty acids
Micelle
Glycerol
Protein
Chylomicrons
Triglyceride
Lacteal (lymph)
Long- chain fatty acids
Capillary network
Chylomicron
Blood vessels
To blood
To liver
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Lipid Absorption

• once inside intestinal cells
• packed with protein into chylomicron
• released into lymphatic system
• enter bloodstream near the heart
• carried by blood for use or storage
• blood analysis indicates types of fat the diet
  has been delivering to the body

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Absorption of Fat
Small intestine
Stomach
Monoglyceride
Short-chain fatty acids
Medium-chain fatty acids
Micelle
Glycerol
Protein
Chylomicrons
Triglyceride
Lacteal (lymph)
Long- chain fatty acids
Capillary network
Chylomicron
Blood vessels
To blood
To liver
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Lipid Transport

• lipoproteins fat transporters
• chylomicrons
• transport diet-derived lipids, mostly
  triglycerides
• triglycerides are removed as they pass through
  the body
• within 14 hours, most triglycerides are depleted
• liver picks up the pieces and use or recycle the
  pieces

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• VLDL very low density lipoprotein
• transport lipids synthesized in live to other
  parts of the body
• liver uses fatty acids in blood to make other
  fatty acids and cholesterol
• triglycerides are removed from VLDL at they move
  through the body, becoming cholesterol dense
• eventually become LDL

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• LDL low density lipoproteins
• cholesterol rich
• are available to all tissue cells

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• HDL high density lipoprotein
• made by the liver to carry cholesterol from cells
• back to the live and recycled or disposed

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HDL or LDL

• LDL bad
• associated with high risk of heart attack
• HDL good
• protective effect for heart

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Controlling LDL and HDL

• lower LDL or raise HDL
• weight control
• unsaturated instead of saturated fat
• fibers
• phytochemicals
• moderate alcohol consumption
• physical activity

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Essential Fatty Acids

• linoleic acid/omega-6
• found in vegetable oils and meats
• linolenic acid/omega-3
• fatty fish

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Role of Lipids

• provide energy
• insulation
• protection against shock
• cell membrane structure
• deficiencies
• retarded growth, skin lesions, kidney and liver
  disorders

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Lipid Metabolism

• fat gives us 2X the energy of carbs and proteins
• efficient storage in adipose tissue
• food fat is converted to body fat by absorbing
  parts and putting back together again inside the
  cell
• very little energy is needed

Large central globule of (pure) fat
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• fat supplies 60 of body's energy during rest
• more during activity
• when needed fat (triglyceride) is dismantled and
  released as glycerol and fatty acids into the
  blood where it is easily accessible by the cells

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Health Effects

• heart disease
• elevated blood cholesterol
• risks from saturated fats
• mostly associated with LDL cholesterol
• risks from trans fats
• alter blood cholesterol the same way saturated
  fats do
• dietary cholesterol
• implicated in raising blood cholesterol

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Health Benefits

• monounsaturated and polyunsaturated fats
• lower possibility of heart disease
• Omega-3 fats
• protects against blood clots, irregular heart
  beats and lowers blood pressure

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Obesity

• fat contributes more than 2X the kcalories/gram
  as carbs or proteins

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Recommended Intakes

• no RDA or upper limits on fat intake has been set
• suggest a diet low in saturated fat, trans fat,
  cholesterol
• provides 20-35 of energy
• Daily Values have been place on food labels using
  30 as guideline

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Groceries

• fats and protein in animal foods
• fats and carbohydrates in plant foods
• vitamins A, D, E, K go hand in hand with fat
• flavor, texture, palatability
• meat
• trim the fat
• use soy protein instead of animal protein

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Groceries

• milk and milk products
• fat free and low fat milk provides the same or
  more protein, calcium as whole milk
• fermented milk products may lower blood
  cholesterol
• veggies, fruits, grains
• lower the content of saturated fat, cholesterol,
  and total fat
• fill up on these little or no fat foods

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Groceries

• invisible fat
• marbling in steak, cheese, fried foods, baked
  goods, chocolate

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Choose Wisely
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Fat Replacers

• fat replacers
• carbs or proteins that replace some of the
  function of fat
• still contribute some energy during digestion

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Artificial Fats

• chemically produced substances made to mimic the
  sensory and cooking attributes of fat
• resistant to digestion
• olestra
• passes through the system unabsorbed
• binds to some vitamins
• food needs to be fortified
• FDA approved

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Butter and Margarine Labels Compared
Margarine (tub)
Margarine (stick)
Butter
Margarine (liquid)
INGREDIENTS Vegetable oil blend (partially
hydrogen- ated and liquid soybean oils) water,
sweet cream butter- milk, salt, vegetable
mono- and diglycerides, soy lecithin, citric
acid, artificial flavor, vitamin A, colored with
beta carotene.
INGREDIENTS Cream, salt.
INGREDIENTS Water, liquid soybean oil,
partially hydrogenated soybean oil, sweet cream,
buttermilk, gelatin, salt, vegetable mono- and
diglycerides, soy lecithin, lactic
acid, artificial flavor, vitamin A, colored with
beta
INGREDIENTS Liquid soybean oil, water,
sweet cream buttermilk, salt, partially
hydrogenated cottonseed oil, vegetable mono- and
diglycerides, soy lecithin, citric
acid, artificial flavor, vitamin A, colored with
beta carotene.