NUT Exam 3 part 1

Chapter 6 (lipids)

Triglycerides

main form of lipids in food and body (storage)

functions of lipids

• provide energy

• Efficient storage of energy 

• Insulation and protection

• Lubricant

• Regulatory processes 

• Cell structure, synthesis and repair

• Absorption and transport of fat-soluble vitamins 

• Satiety

Esterification

the process of attaching fatty acids to glycerol; in the process releasing one water molecule

Properties of lipids

• Do NOT dissolve in water (not water soluble) 

• Fats are solid at room temperature 

• Oils are liquid at room temperature 

• Energy dense (9 kcal / gm) 

• Provide satiety, flavor, mouthfeel

Cholesterol is a…

precursor for estrogen and bile

Saturated Fatty acid

filled to capacity (solid fats)

• coconut oils, palm oils

unsaturated fatty acids

H missing (oils)

• double bonds instead

Omega-3 (alpha linoleic acid)

Omega-6 (linoleic acid)

omega-3

• first double bond is after the 3rd carbon from the omega end

fatty fish, walnuts, oils from canola, soy and flax seeds

Omega-6

• first double bond is located after the 6th carbon from the omega end

most plant oils (safflower, sunflower, corn and cottonseed)

Sterols Functions

• cellular structure

• myelin

• bile acid precursors

• vitamin D

Sterols Structure

Carbon and hydrogen RINGS

cholesterol sterols

steroid hormones (ex. estrogen and testosterone)

adrenal hormones (ex. corticosteroids)

cell membranes

• NOT essential in the diet

Cholesterol

found only in animal foods, not plants (vegetarian diets have none)

exists in diets in milligram quantities

does NOT yield energy

may increase CVD risk in excess

liver makes cholesterol

not essential in human diets

phospholipids

lipids with a phosphate group, making one end attract to water, while the rest still attracts to liquid

• ex: lecithin

Phospholipids Functions

• cell membranes

• lubricants: joints and GIT

• Emulsifiers

  • bile acids

  • micelles

• NOT essential in diet

RDA Lipids

No RDA (Daily value= 65g)

US dietary guidelines: 20-35%

Lipid Digestion

1. mouth - lingual lipase digested

2. stomach - gastric lipase digested

3. liver - bile emulsifies fat

4. pancreas - secretes pancreatic lipase, etc

5. small intestine - bile is reabsorbed in the ileum, etc

6. large intestine - less than 5%

lipoproteins

protein-containing lipid transporters in blood

Types of Lipoproteins

1. chylomicrons

2. VLDL

3. LDL

4. HDL

HDL

High density lipoprotien

• “good”

removes lipids from body cells

LDL

• “bad”

transport lipids to body cells on regular basis

chylomicrons

1st pass after absorption

VLDL

2nd pass after absorption

HDLs role in removing Blood LDL

• highest proportien of protein

• produced by the liver and intestine

• roams the bloodstream, picking up cholesterol from dying cells

• donates cholesterol to other lipoproteins for transport back to liver for excretion

• helps to block the oxidation of LDL

• slows development of CVS

Cardiovascular Disease (CVD)

Leading cause of death in the USA

• 1 million deaths a year

• 13 million people have some form of CVD symptom

• about 50% of Americans have elevated total cholesterol levels

CVD Risk Testing

Physiological tests

• triglyceride levels

• total cholesterol

• LDL cholesterol

• HDL cholesterol (want it to be high)!!!

• blood pressure (hypertension)

• blood glucose (diabetes)

• Blood clotting status

Controllable CVD risk factors

smoking

excess body fat

sedentary lifestyle

diet high in fat, trans fat, sat.fat, cholesterol, sodium

diet low in fobers, potassium, some B-vitamins and antioxidants

non-controllable CVD risk factors

family history

genetics

age

Saturation

amount of H on C of the fatty acid chain

Hydrogenation

turns liquid oils into solid fats

essential fatty acids

alpha-linoleic acid and linoleic acid

phospholipids consist of…

glycerol, 2 fatty acids and phosphate

enzymes

control oxidation-reduction reactions in the body

what turns rancid the fastest

polyunsaturated fats

• soybean oil

Omega-3 fatty acids

• alpha-linoleic acids

• Eicosapentaenoic acids (EPA)

• Docosahexaenoic acid (DHA)

Omega-6 fatty acids

• Linoleic acids

• Dihomo-gamma-linoleic acid

• arachidonic acid

Eicosanoids

substances that produce diverse hormonr-like effects on the body

Hydrogenation

converts unsaturated fats into more saturated solid ones.

ergosterol

type of sterol found in plants

• not in animal foods