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Chapter 3

LIFESCI 2N03 Chapter Notes - Chapter 3: Lecithin, Unsaturated Fat, Choline


Department
Life Sciences
Course Code
LIFESCI 2N03
Professor
Janet Pritchard
Chapter
3

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Chapter 3 Textbook Notes
September 21, 2018
4:16 PM
Learning Goals
1. Compare and contrast the different types of fat.
2. Describe the composition of triglycerides, and features that make dietary fats different
from each other.
3. Explain how dietary fat is digested and transported.
4. Discuss the requirements for the different types of fat in our diet.
3.1 What is Dietary fat?
o Lipids: the term for a class of nutrients that includes phospholipids,
sterols, and the more well known type triglycerides
o Oil and butter are made of triglycerides with different types of fatty
acid (saturated and unsaturated)
o Eggs are a source of saturated and unsaturated fats, protein, vitamins
A, D, E, B2, B9, B12 and selenium (an antioxidant)
Also contain lecithin which is a phospholipid containing two fatty
acids, a phosphate group and molecule of choline
o Phospholipids only accounts of up to 10% of total lipid dietary intake
They have a hydrophobic (soluble in fat) tail and
hydrophilic(soluble in water) head
o Lecithin delivers nutrients to the body, such as choline, glycerol and
fatty acids
In eggs it acts as an emulsifier
Soy lecithin can be used a substitute for vegans, peanuts and wheat
germs can also be used
Researchers believe that soy lecithin may help decrease
cardiovascular disease risk by inhibiting cholesterol absorption
and promoting cholesterol excretion from the body

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o Sterols: another type of lipid
Cholesterol is the sterol found in animal products
Egg yolk contains about 200 mg of cholesterol
Approximately 40-60% of cholesterol found in foods is absorbed
and most the cholesterol in our bodies is synthesized
endogenously (our body makes it)
Having too much cholesterol is bad but we need some cholesterol
to make sex hormones, adrenal hormones and bile acids
There are no biological needs for cholesterol in our diet
Many studies however have shown that an increase of 100 mg/day
of dietary cholesterol can result in a 0.050.1 mmol/L increase in
total serum cholesterol (80% of which is LDL cholesterol
Phytosterols: a plant sterol
More than 40 plant sterols have been identified, but the most
abundant are beta-sitosterol, campesterol and stigmasterol
Plants also contain stanols, similar to sterols but they have no
double bonds in the hydrocarbon
Plant sterols and stanols can help lower cholesterol, 2 grams
of them can reduce cholesterol absorption by 50% but this is
the maximum reduction from these
How long do you have to consume these fortified margarines
to experience a cholesterol-lowering effect? Trials ranged
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from 1-52 weeks, and the average reduction in LDL
cholesterol was 0.33mmol/L for people age 30-39
years, 0.43 mmol/L for people age 40-49 years and 0.54
mmol/L for people age 50-59 years.
This isn't bad considering that studies show that for each
1mmol/L reduction in LDL cholesterol, the risk of a
cardiovascular disease-related event (for example, heart
attack) decreases by about 20%
Another sterol is vitamin D
We only get a small portion of vitamin D naturally
through food, so the GOC requires the fortification of
milk and margarine products with vitamin D
Triglycerides: made of one glycerol and three fatty acids
Fatty acids are chains of 4-24 carbons and they can have single
or double bonds
Unsaturated: one or more double bonds
Saturated: no double bonds so it has more hydrogen
Typically saturated fats are more solid at room temperature
and unsaturated fats are more liquid
Coconut oil which is mainly made of saturated fats is very soft
or almost liquid at room temp because the triglyceride
carbon chain is short (12 C) compared to other triglyceride
containing items like butter
Monounsaturated: triglycerides that have fatty acids with
one double bond
Polyunsaturated fats: triglycerides that are composed of fatty
acids with more than 1 double bond
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