6. Lipids: Chemistry and Nutritional Significance
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Numbering of carbon atoms. The systematic (IUPAC) C-x numbers are in blue.
The ω−x" labels are in red. The Greek letter labels are in green. Note that
unsaturated fatty acids with a cis configuration are actually "kinked" rather than
straight.
7. Omega-3 and Omega-6 Fatty
Acids Compared
Lipids: Chemistry and Nutritional Significance
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8. Triglycerides
• Three fatty acids attached
to a glycerol
• Formed via series of
condensation reactions
• Usually contain mixture of
fatty acids
Lipids: Chemistry and Nutritional Significance
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9. Condensation of Glycerol and
Fatty Acids to Form a Triglyceride
Lipids: Chemistry and Nutritional Significance
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10. Diagram of Saturated and
Unsaturated Fatty Acids Compared
Lipids: Chemistry and Nutritional Significance
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15. Phospholipids participate in the reverse cholesterol transport and thus
help in the removal of cholesterol from the body.
Phospholipids act as surfactants (agent lowering surface tension).
Cephalins participat in blood clotting.
Phospholipids( phosphatidyl inositoal ) involved in signal transmission across
membranes.
16. Sterols
• Food sources
• Cholesterol
• Plant sterols
• Roles of sterols
• Made in the body
• Structural component of
cell membranes
Lipids: Chemistry and Nutritional Significance
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17. Cholesterol Related compounds: 7-dehydrocholesterol (functions as
a cholesterol precursor in blood serum) gets converted in vivo
(epidermal cells) to Vitamin D by the action of sunlight
Lipids: Chemistry and Nutritional Significance
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18. Fat Digestion in the GI Tract
Lipids: Chemistry and Nutritional Significance
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20. Lipid Digestion in the
Small Intestine
Lipids: Chemistry and Nutritional Significance
• Cholecystokinin (CCK)
• Gall bladder releases bile
• Bile acts as emulsifier
• Pancreatic lipase
• Hydrolysis
• Triglycerides and phospholipids
• Bile routes
• Effect on blood cholesterol levels
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21. Emulsification of Fat by Bile
Lipids: Chemistry and Nutritional Significance
4/25/2024 5:21 PM 21
22. Stepped Art-
Fat
Watery GI
juices
Fat
In the stomach,
the fat and
watery GI juices
tend to separate.
The enzymes in
the GI juices
can’t get at the
fat.
When fat enters
the small intestine,
the gallbladder
secretes bile. Bile
has an affinity for
both fat and water,
so it can bring the
fat into the water.
Bile’s emulsifying
action converts
large fat globules
into small droplets
that repel each
other.
After
emulsification,
more fat is
exposed to the
enzymes, making
fat digestion more
efficient.
Enzyme
Emulsified
fat
Bile
Enzymes
Emulsified
fat
Emulsified
fat
4/25/2024 5:21 PM
Lipids: Chemistry and Nutritional Significance
22
23. Hydrolysis of a Triglyceride
Lipids: Chemistry and Nutritional Significance
4/25/2024 5:21 PM 23
25. Lipid Absorption
Lipids: Chemistry and Nutritional Significance
• Directly into bloodstream
• Glycerol and short- and medium-chain fatty acids
• Lymphatic system
• Micelles diffuse into intestinal cells
• Reassembled into triglycerides
• Packed with proteins into transport vehicles called
chylomicrons
• Bypass liver at first
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27. Lipid Transport
Lipids: Chemistry and Nutritional Significance
• Four main types of lipoproteins
• Chylomicrons
• Largest and least dense
• Transport diet-derived lipids
• Liver removes remnants from blood
• Very-low-density lipoproteins (VLDL)
• Made in the liver
• Proportion of lipids shifts
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28. Lipoprotein Types
Lipids: Chemistry and Nutritional Significance
• Low-density lipoproteins (LDL)
• Cell needs
• Liver regulation
• High-density lipoproteins (HDL)
• Remove cholesterol from cells
• Carry cholesterol to liver for recycling
• Anti-inflammatory properties
• Health implications
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29. Sizes and Compositions of the
Lipoproteins
Lipids: Chemistry and Nutritional Significance
4/25/2024 5:21 PM 29
31. Roles of Triglycerides
Lipids: Chemistry and Nutritional Significance
• Provide the cells with energy
• Virtually unlimited ability to store fat energy
• Adipose tissue stores body fat
• Secretes hormones (adipokines)
• Other uses of fat in the body
• Skin insulation
• Shock absorption
• Cell membrane material
• Cell signaling pathways
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33. Essential Fatty Acids
• Must be supplied by
the diet
• Linoleic acid
• Linolenic acid
• Can be used to make
other fatty acids
Lipids: Chemistry and Nutritional Significance
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34. Omega-6 and Omega-3 Fatty
Acids
Lipids: Chemistry and Nutritional Significance
• Linoleic acid – Omega-6 fatty acid
• Sources: vegetable oils and meats
• Linolenic acid – Omega-3 fatty acid
• Cannot be made in the body
• Must be supplied by food
• DHA
• EPA
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35. Eicosanoids
Lipids: Chemistry and Nutritional Significance
• Eicosanoids
• “Hormonelike”
• Health benefits
• Omega-6 to Omega-3 ratio
• Fatty acid deficiencies
• Rare in the United States and Canada
• Symptoms
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36. A Preview of Lipid Metabolism
Lipids: Chemistry and Nutritional Significance
• Adipose cells store fat after meals
• Lipoprotein lipase
• Hydrolyzes triglycerides
• Triglycerides reassembled inside adipose cells
• Using fat for energy
• Fat supplies 60 percent of energy needs during
rest
• Energy deprivation
• Fasting: fat and lean protein tissue used for energy
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37. Health Effects of Saturated Fats,
Trans Fats, and Cholesterol
Lipids: Chemistry and Nutritional Significance
• Current American diet
• Excessive amounts of solid fats
• Blood lipid profile
• Heart disease
• Elevated LDL cholesterol a risk factor
• Saturated fats increase LDL cholesterol, promote
blood clotting
• Dietary choices
• Trans fats – increase LDL cholesterol
• Dietary cholesterol
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38. Fat Links to Cancer and Obesity
Lipids: Chemistry and Nutritional Significance
• Cancer
• Dietary fat and cancer risk
• Differs for various types of cancer
• Promotion rather than initiation of cancer
• Obesity
• Cutting fat from diet reduces kcalories
• Dietary recommendations
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39. Recommended Intakes of Saturated
Fat, Trans Fat, and Cholesterol
Lipids: Chemistry and Nutritional Significance
• DRI and Dietary Guidelines
• 20 to 35 percent of daily energy from fat
• Less than 10 percent of daily intake from
saturated fat
• As little trans fat as possible
• Less than 300 mg cholesterol
• Avoid getting too little fat
• Recommendation: one teaspoon of fat with every
meal
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40. Health Effects of Monounsaturated
and Polyunsaturated Fats
• Heart disease
• Replace saturated fats with
unsaturated fats
• Regular consumption of
omega-3 fatty acids
• Suppresses inflammation
• Cancer
• Omega-3 fatty acids from
food
• Supplements
Lipids: Chemistry and Nutritional Significance
4/25/2024 5:21 PM 40
41. Replacing Saturated Fat
with Unsaturated Fat
Lipids: Chemistry and Nutritional Significance
Portion sizes have been adjusted so that each of these foods provides approximately 100 kcalories. Notice that
for a similar number of kcalories and grams of fat, the second choices offer less saturated fat and more
unsaturated fat.
Replace these foods…
Saturated
Fat (g)
Unsaturated
Fat (g)
Total
Fat (g)
Butter (1 tbs)
7 4 11
Bacon (2 slices)
3 6 9
Potato chips (10 chips)
2 5 7
Cheese (1 slice)
4 4 8
Steak (1'/2 0z)
2 3 5
Totals
18 22 40
…with these foods
Saturated
Fat (g)
Unsaturated
Fat (g)
Total
Fat (g)
Olive oil (1 tbs)
2 9 11
Sunflower seeds (2 tbs)
1 7 8
Mixed nuts (2 tbs)
1 8 9
Avocado (6 slices)
2 8 10
Salmon (2 oz)
1 3 4
Totals
7 35 42
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42. Recommended Intakes of Mono-
and Polyunsaturated Fats
Lipids: Chemistry and Nutritional Significance
• 20 to 35 percent of kcalories from fat
• Includes essential fatty acids
• AI have been established
• DRI
• Linoleic acid: 5-10% of daily energy
• Linolenic acid: 0.6-1.2% of daily energy
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43. Selecting Groceries
Lipids: Chemistry and Nutritional Significance
• Fat-soluble vitamins
• A, D, E, and K
• Flavor, texture, and palatability
• Protein foods
• Selections
• Milk and milk products
• Selections
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44. Cutting Fat Cuts kCalories and
Saturated Fat
Lipids: Chemistry and Nutritional Significance
4/25/2024 5:21 PM 44
45. Grocery Choices
Lipids: Chemistry and Nutritional Significance
• Vegetables, fruits, and grains
• Lowers consumption of various fats in the diet
• Provides phytochemicals
• Solid fats and oils
• Fried and baked goods
• Choose wisely
• Unprocessed foods
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46. Food Labeling
Lipids: Chemistry and Nutritional Significance
• Total fat, saturated fat, trans fat, and
cholesterol
• Compare products
• Percent Daily Value versus percent kcalories
from fat
• Fat replacers
• Types
• Risks
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47. High-Fat Foods –
Friend or Foe?
Highlight 5
Lipids: Chemistry and Nutritional Significance
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48. Guidelines for Fat Intake
Lipids: Chemistry and Nutritional Significance
• Limit saturated fat and trans fat intake
• Moderate kcalories
• Enough fat for good health
• Not too much of the harmful fats
• DRI recommendations
• Compatible with low rates of disease
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49. High-Fat Foods and Heart
Health
Lipids: Chemistry and Nutritional Significance
• Olive oil
• Benefits for heart health
• Replace saturated fats
• Nuts
• LDL cholesterol
• Fat composition
• Benefits for heart health
• Cautious advice for dietary inclusion
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50. Fish
Lipids: Chemistry and Nutritional Significance
• Omega-3 fatty acids
• Benefits for heart health
• Environmental contaminants
• Farm raised versus wild
• Dietary recommendations
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51. High-Fat Foods and Heart
Disease
Lipids: Chemistry and Nutritional Significance
• Saturated fat the top dietary determinant of
LDL cholesterol
• Sources of saturated fat in the U.S.
• Meats
• Whole milk products
• Tropical oils
• Zero saturated fat is not possible
• Trans fat
• Limit hydrogenated foods
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53. The Mediterranean Diet
Lipids: Chemistry and Nutritional Significance
• Features of a traditional Mediterranean diet
• Low in saturated fat
• Very low in trans fat
• Rich in monounsaturated and polyunsaturated fat
• Rich in complex carbohydrate and fiber
• Rich in nutrients and phytochemicals
• Benefits for heart disease risk
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