Chapter 5 - Fats
What does trans fat consumption appear to do?
Elevate the risk for CAD
How does saturated fat contribute to heart disease?
1 Large amounts of saturated fat produce more LDL to circulate in the blood. 2 The cholesterol carried in the LDL is more likely to be attacked by oxygen, which in turn attracts big scavenger cells called macrophages. These cells are able to surround, engulf, and digest microorganisms and cellular debris. 3 The macrophages consume the oxidized material that accumulates in a modified form, called foam cells. 4 The foam cells cluster under the lining of the artery wall, forming bulges that cause fatty streaks, which is the first event in plaque formation. 5 The foam cells produce chemicals that further damage the artery wall and cause changes that produce artery-clogging plaque.
Describe Triglycerides
Triglyceride is the largest class of lipids found in food and body fat. Triglycerides are compounds consisting of three fatty acids and one glycerol molecule
Why do saturated fatty acids raise blood cholesterol levels?
by providing the liver with the best building blocks for making cholesterol
What are some plant sources of Omega-3 fatty acids?
canola oil, walnuts and walnut oil, soybean and soybean oil, flaxseed ground and oil, wheat germ and oat germ, green leafy vegetables
What is satiety?
feeling full and satisfied
Plants contain mostly which type of fat?
polyunsaturated
What do blood LDL levels reflect?
reflect the amount of cholesterol brought to cells that have the potential to be dropped off along the way to clog vessels and arteries, contributing to plaque formation
What are the functions of HDLs?
remove cholesterol from the cell, bringing it to the liver for disposal
Animal sources contain mostly which type of fat?
saturated
What food sources contain lecithin?
soybeans, egg yolks
What are the functions of chylomicrons?
transport absorbed fats from the intestinal wall to the liver cells. Fats are then used for synthesis of lipoproteins
What are good fish sources of Omega-3 fatty acids?
tuna, salmon, bluefish, halibut, sardines, and rainbow trout
When does too much food cholesterol become a problem?
when it is eaten in conjunction with very high-fat diets. Sometimes, this extra cholesterol in the blood may be dropped off, staying in the vessels and arteries. It is a factor involved in the accumulation of plaques that result in blockage in the arteries call atherosclerosis, or CAD.
What four forms of lipoproteins are found in the body?
• chylomicrons • very low-density lipoproteins • LDLs • HDLs
What are the food functions of fats?
• source of energy • Palatability • satiety and satiation • food processing • nutrient source
What are the physiologic functions of fats?
• stored energy • organ protection • insulation (think more about nerves than warmth)
What are borderline-high LDL levels?
130-159 mg/dL
Describe an action plan for gradual reduction of dietary fat
1For 1 week, record all food and beverages consumed. 2Based on reading this chapter, assess which foods are likely to be high in fat. Particularly note if one high-fat food item, such as whole milk, is consumed often or if a certain meal or snack regularly includes fatty foods. Perhaps scrambled eggs and bacon are eaten almost every morning for breakfast, and an afternoon coffee break always includes either a sweet Danish pastry or a huge, buttery muffin. 3The next week, choose one item and either reduce consumption or replace it with a lower-fat substitute. Instead of whole milk, use 2% or 1% fat milk, or replace the coffee break treat with an English muffin with a bit of butter or margarine and jelly. 4The following week, select another food item or meal and make a simple substitution.
What are borderline-high total cholesterol levels?
200-239 mg/dL
What is the recommended percentage of calories from fat?
25-30%
How many calories in a gram of fat
9
How much saturated fatty acids should be consumed?
<10%kcals
What are ideal LDL levels?
<130mg/dL
What should triglyceride levels be?
<150
Compare and contrast triglycerides and phospholipids
Similar to triglycerides, phospholipids contain fatty acids, but they have only two fatty acids; the third spot contains a phosphate group.
What determines the density or weight of a lipoprotein?
The amount of fat and protein. The more fat and lipid substances present, the lower the density (or lighter) of the compound.
Describe linoleic acid
The final double bond is at the sixth carbon from the omega end of the chain in linoleic acid (see Figure 5-5, C), the main member of the omega-6 family
Describe linolenic acid
The first double bond is at the third carbon atom from the omega end in linolenic acid (see Figure 5-5, D), the main member of the omega-3 family.
Are linoleic and linolenic acid essential nutrients?
Yes. Body does not make them.
what is an emulsifier?
a substance that works by being soluble in water and fat at the same time
How much cholesterol a day?
<300mg
What are the changes to fat levels recommended for those at high risk for CAD?
<7% kcal of saturated fat <200mg cholesterol
How much Omega-6 oils do Americans consume?
Americans consume an abundance of linoleic acid from consumption of large amounts of vegetable oils, such as margarine and salad dressing, and large amounts of prepared foods. Another source of linoleic acid may be animal foods; for example, although poultry fat is predominantly saturated, it also contains some PUFA, including linoleic acid.
Describe sterols
As a lipid group, sterols are critical components of complex regulatory compounds in our bodies and provide basic material to make bile, vitamin D, sex hormones, and cells in brain and nerve tissue.
Describe the process of digestion of lipids in the small intestine
Fats entering the duodenum initiate the release of cholecystokinin (CCK) hormone from the duodenum walls. CCK, as described in Chapter 3, then sparks the gallbladder to release bile into the small intestine. The bile emulsifies fats to facilitate digestion. Mechanical digestion through muscular action allows for increased exposure of the emulsified fat globules to pancreatic lipase. This enzyme is the primary digestive enzyme that breaks triglycerides into fatty acids, monoglycerides, and glycerol molecules.
What are the functions of LDLs?
LDLs carry cholesterol throughout the body to tissue cells for various functions.
Describe lecithins
Lecithins are the main phospholipids. Lecithin is a constituent of lipoproteins—carriers or transporters of lipids—including fats and cholesterol in the body. This characteristic has earned lecithin a reputation for carrying fat and cholesterol away from plaque deposits in the arteries.
Describe the process of digestion of lipids in the stomach
Mechanical digestion continues through the strong actions of peristalsis. Fat-splitting enzymes such as gastric lipase hydrolyze some fatty acids from triglycerides.
Are phospholipids an essential nutrient?
No. Body makes them.
Are sterols an essential nutrient?
No. Body makes them.
Does dietary lecithin help make the body's transport system more efficient?
No. Dietary lecithin is simply digested and used by the body as any other lipid.
Do Americans generally consume enough Omega-3?
Nope. Usually fish sourced.
Why does fat slow down digestion?
The word "shrub" is derived from the Arabic sharbah, which means "a drink." ("Sherbet" and "syrup" also come from this Arabic root.)
What is satiation?
another, different aspect of fat consumption that occurs during, not after, eating. In contrast to satiety, satiation tends to increase our desire to eat additional fatty foods, not less. The effect of fat on satiation is likely to be more important than its effect on satiety and may lead to overeating.2 A situation that often occurs with the last slice of pizza provides a good example: You want it, you eat it, and half an hour later, you feel too full.
What are the only major plant sources of saturated fatty acids?
cocoa butter, coconut and palm oils
What are plaques?
deposits of fatty substances, including cholesterol, that attach to arterial walls
What are optimal HDL levels?
≥60mg/dL
What are ideal total cholesterol levels?
<200mg/dL
Describe the process of digestion of lipids in the mouth
The mouth's primary fat digestive process is mechanical, as teeth masticate fatty foods. The glands of the tongue produce a fat-splitting enzyme (lingual lipase) released with saliva that begins digestion of long-chain fatty acids such as those found in milk.
What are the food sources of sterols?
The only food sources of cholesterol are animal and include beef, pork (bacon), chicken, luncheon meats, eggs, fish, and dairy products (milk, butter, and cheeses); plant foods do not contain cholesterol.
What are the functions of very low-density lipoproteins?
leave the liver cells full of fats and lipid components to transfer newly made (endogenous) triglycerides to the cells.
Describe phospholipids
lipid compounds that form part of cell walls and act as a fat emulsifier
What is the major culprit for elevated cholesterol levels?
not dietary food cholesterol but too much food fat (dietary triglycerides), particularly saturated fats
What are high LDL levels?
≥160 mg/dL
What are high total cholesterol levels?
≥240 mg/dL
