Dietary Fat

Question 1

Dietary Fat: functions

Answer 1

1. Fuel & fuel reserve
2. Essential FA
3. Carrier for fat soluble vitamins
4. Insulation (subcutaneous fat)
5. Protection (essential organs)
6. Brain tissue, myelin sheaths
7. Cell membrane (phospholipid)
8. Hormone and prostaglandin synthesis

Question 2

Fatty Acid Classification?

Answer 2

Short chain fatty acids (1-6 carbons): Saturated FA

Medium chain fatty acids (8-14 carbons): Saturated FA

Long Chain fatty acids (16-20 carbons): Saturated FA, Monounsaturated FA, polyunsaturated FA

20: 5 n-3:
20: no. of carbon atoms
5: no. of double bonds

n-3: Location of 1st double bond

Question 3

Lipoprotein metabolism:

Answer 3

Lipoproteins:
• Transport lipids and cholesterol (exo. & endo.) in the body.

• Contain lipid & cholesterol encased by protein and phospholipids

Chylomicrons:
• Triglyceride rich

• Formed in intestine from dietary fat

Very low density lipoprotein (VLDL):
• Triglyceride rich, formed in liver

Low density lipoprotein (LDL):
• Cholesterol rich

• Delivers cholesterol to tissues
• Atherogenic

High density lipoprotein (HDL):
• Carries cholesterol away from vessel walls.

• Assists with lipoprotein lipase (LPL) activation

Question 4

Cholesterol intake?

Answer 4

The influence of dietary cholesterol on blood cholesterol is small because of the reduction in
endogenous synthesis when exogenous cholesterol intake is increased and vica versa.

Question 5

Trans Fatty Acids- mechanism?

Answer 5

Conclusion: Increased cholesteryl ester transfer protein (CETP) activity
contributes to the increase in LDL and decrease in HDL cholesterol associated with diets high in trans fatty acids.

Question 6

FA Type & Serum lipoproteins:

Answer 6

Conclusion: Replacement of 1% energy intake from MUFA with trans fat is associated with a +0.040mmol/L increase in [LDL] and -0.013mmol/L decrease in [HDL].

Question 7

Trans Fat & CHD Risk: Methods and Results?

Answer 7

Methods:
• Nurses Health Study (121,700 W)

• 20 year follow up (78,778W)

Results:
• 1766 CHD cases

• 1241 non-fatal MI, 525 deaths

• Trans fat stratified according to
quintiles

• Trans fat intake ≥1.9% EI is
associated with a (19-33%)
increased risk of CHD.

Question 8

Dietary sources of fatty acids: VLDL?

Answer 8

Lauric: —>

Myristic: —>

Palmitic: —>

oleic: —> (negative)

Linoleic: —> (negative)

Eicosapentaenoic: —>, —> (negative)

Doscosahexaenoic: —>, —> (negative)

Question 9

Dietary sources of fatty acids: LDL?

Answer 9

Lauric: —>

Myristic: —>, —>

Palmitic: —>, —>

oleic: —>, —> (negative)

Linoleic: —>, —>, —> (negative)

Eicosapentaenoic: —>

Doscosahexaenoic: —>

Question 10

Dietary sources of fatty acids: HDL?

Answer 10

Lauric: —>

Myristic: —>

Palmitic: —>

oleic: —> (negative)

Linoleic: —> (negative)

Eicosapentaenoic: —> (negative)

Doscosahexaenoic: —> (negative)

Question 11

Saturated Fat intake?

Answer 11

Characteristics:
• Solid at room temperature

Dietary Sources:
• Animal
• Meat, milk, butter, cheese
• Plant (few)
• Coconut oil

DRV Drivers:
• ↑[LDL]
• ↑[Total Cholesterol]
• ↑CVD risk

Saturated Fatty acid DRV:
• ≤10% of energy intake

Current Intake:
• Men – 28.4g/d (11.9%)
• Women – 22.1g/d (12.1%)

Question 12

Polyunsaturated Fat Intake?

Answer 12

Characteristics:
• Contain ≥2 double bond (Liquid at room temp)

• Susceptible to oxidation

• Omega-3 & Omega-6– Different metabolic effects
– Eicosanoids
– Blood clotting
– Inflammation
– Immunity

Dietary Sources:
• Oils, nuts, seeds, fish oil

PUFA DRV:
• ~6 to ≤10% of energy intake
• (≥ 1% from linoleic acid and ≥0.2% α-linolenic acid) (Goal = prevent deficiency)

Current N-3 Intake:
• Men – 2.2g/d (0.9%)
• Women – 1.8g/d (1.0%)

Current N-6 Intake:
• Men – 11.2g/d (4.8%)
• Women – 8.8g/d (4.9%)

Question 13

Trans Fat Intake?

Answer 13

Characteristics:
• Double bond is in trans form not cis
form.

Dietary Sources:
• Rare in nature (eg. manufactured)

• Enable spreadable options
• Milk, cheese, beef, lamb, margarine

DRV Drivers:
• When substituted for SFA, Trans FA:
– ↑ [LDL]
– ↓ [HDL]

• Increased CHD risk

Trans Fatty acid DRV:
• ≤2% of dietary energy intake

Current Intake:
• Men – 1.5g/d (0.6%)
• Women – 1.2g/d (0.6%)

Question 14

Dietary Fat Intake?

Answer 14

Dietary Components:
• Triglyceride (main; 95%)
– Fatty  Acids include:
– Saturated
– Monounsaturated
– Polyunsaturated
– Trans

• Phospholipid (small)
– Diglyceride + phosphoric acid

• Cholesterol esters

Total fat intake DRV:
• ≤35% of energy intake

Current Intake:
• Men (19-64y)– 77.7g/d (32.8%)
• Women (19-64y)– 60.1g/d (33%)

Question 15

Cholesterol Intake?

Answer 15

Function:
• Vital component of cell membrane

• Precursor to bile (fat digestion)
• Precursor to steroid hormones.

Body Stores:
• The body comprises ~140g of cholesterol (~8g in plasma)

DRV:
• No DRV current set, but population average (in 1994) should not increase
(~245mg/d).

Current Intake:
• Men – 304mg/d

• Women – 214mg/d

Question 16

DRV’s - Fat:

Answer 16

Total fat intake:
• ≤35% of energy intake (COMA 1994)

Saturated Fatty acids:
• ≤10% of energy intake (SACN 2019)

Monounsaturated fatty acids:
• No specific recommendation for MUFA (COMA 1994), previously 12% of energy intake (COMA 1991)

Polyunsaturated fatty acids:
• ~6 to ≤10% of energy intake (COMA 1991)
– α-linolenic acid ≥0.2% of energy intake
– Linoleic acid - ≥1% of energy intake

Trans fatty acids:
• ≤2% of energy intake (SACN 2007)

Cholesterol:
• No DRV currently, but population average should not increase (245mg/d) (COMA 1994)