1. The Lipids: Triglycerides, Phospholipids, and Sterols

2. Introduction Poor health Too much fat Too little fat
Too much of some kinds of fat
Family of lipids
Triglycerides (fats and oils)
Most abundant in food and body
Phospholipids
Sterols

3. Triglycerides

4. Triglycerides

5. Triglycerides

6. Phospholipids Phospholipids Soluble in fat and water
Emulsifiers in food industry
Promote mixing of oil and fats in watery solution
Lecithin is a phospholipid
Food sources
Eggs, liver, soybeans, wheat germ and peanuts
Roles
Part of cell membranes
Emulsifiers

7. Sterols Sterols (most famous is cholesterol) Food sources
Meats, eggs, fish, poultry and dairy products
Cholesterol is found almost exclusively in animals
Roles of sterols
Body compounds made from cholesterol
Bile acids
Sex hormones
Adrenal hormones
Vitamin D

8. Lipid Digestion

9. Emulsification of Fat by Bile

10. Hydrolysis of a Triglyceride

11. Enterohepatic Circulation of Bile

12. Absorption of Fat

13. Lipid Transport

14. Dietary Fats
Dietary fats more strongly influence the incidence of coronary heart disease (CHD)
Research indicates that the type of fat is more important than the total amount of fat consumed

15. Dietary Fats Plasma Lipids and CHD
Plasma cholesterol may arise either from diet or from endogenous biosynthesis
Cholesterol is transported between the tissues in combination with protein and phospholipids as lipoproteins
Lipoprotein structure (chylomicron)
ApoA, ApoB, ApoC, ApoE (apolipoproteins);
T (triacylglycerol);
C (cholesterol);
green (phospholipids)

16. 1. Low density lipoprotein (LDL) and high density lipoprotein (HDL)
Dietary Fats
Plasma Lipids and CHD
1. Low density lipoprotein (LDL) and high density lipoprotein (HDL)
The level of plasma cholesterol is not precisely regulated, but rather varies in response to the diet
Elevated levels of LDL cholesterol result in an increased risk for CHD
Elevated levels of HDL cholesterol result in a decreased risk for CHD
Abnormal levels of plasma lipids (dyslipidemia) act in combination with smoking, obesity, sedentary lifestyle, insulin resistance and other risk factors to increase the risk of CHD

17. 2. Beneficial effect of lowering plasma cholesterol
Dietary Fats
Plasma Lipids and CHD
2. Beneficial effect of lowering plasma cholesterol
Clinical trials have demonstrated that dietary or drug treatment of hypercholesterolemia is effective in decreasing LDL, increasing HDL, and reducing the risk for cardiovascular events
Diet induced changes are typically 10-20% decrease in cholesterol
Treatment with statin drugs decreases plasma cholesterol by about 30-60%
- HMG-CoA-reductase inhibitors

18. Dietary fats and plasma lipids
Triacylglycerols (TAGs) are quantitatively the most important class of dietary fats
The influence of TAGs on blood lipids is determined by the chemical nature of their constituent fatty acids
Absence or presence of double bonds
Number of double bonds (saturated vs. mono- and polyunsaturated)
Location of the double bonds (ω-6 vs. ω-3)
Cis vs. trans configuration of the unsaturated fatty acids

19. Dietary fats and plasma lipids
1. Saturated fat
Triacylglycerols composed primarily of fatty acids whose hydrocarbons chains do not contain any double bonds
Consumption is positively associated with high levels of total plasma cholesterol and LDL cholesterol, and an increased risk of CHD
Main sources are
Dairy and meat products
Some vegetable oils such as coconut and palm

20. Dietary fats and plasma lipids
1. Saturated fat
Chain lengths of 14C (myristic) and 16C (palmitic) are most potent in increasing serum cholesterol
Stearic acid (18C) found in many foods including chocolate has little effect on blood cholesterol

22. Dietary fats and plasma lipids
2. Monounsaturated fats
TAGs containing primarily fatty acids with one C=C
When substituted for saturated fatty acids, lowers both total plasma cholesterol and LDL cholesterol, but maintain or increase HDL cholesterol
Diets rich in olive oil (high in monounsaturated oleic acid) show a low incidence of CHD (e.g. Mediterranean cultures)

23. Dietary Fats
Mediterranean Diet

24. Dietary fats and plasma lipids 3. Polyunsaturated fats (PUFAs)
Triacylglycerols containing primarily fatty acids with more than one C=C
Effect on cardiovascular disease is influenced by the location of the C=C within the molecule

25. 3. Polyunsaturated fats (PUFAs)
Dietary Fats
3. Polyunsaturated fats (PUFAs)
ω-6 Fatty acids
Long chain PUFAs with the first C=C beginning at the 6th bond position when starting from the CH3 end of the fatty acid molecule
Consumption of fats containing ω-6 PUFAs, principally linoleic acid, 18:2(9,12), obtained from vegetable oils, lowers plasma cholesterol when substituted for saturated fats
Lowers plasma LDL and HDL

26. 3. Polyunsaturated fats (PUFAs)
Dietary Fats
3. Polyunsaturated fats (PUFAs)
ω-6 Fatty acids
Linoleic acid is an essential fatty acid
5-10% of total calories recommended

27. 3. Polyunsaturated fats (PUFAs)
Dietary Fats
3. Polyunsaturated fats (PUFAs)
ω-3 Fatty acids
Long chain PUFAs with the first C=C beginning at the 3rd bond position from the CH3 end
Suppress cardiac arrthymias, reduce serum TAGs, decrease the tendency for thrombosis, lower blood pressure, and substantially reduce the risk of cardiovascular mortality, but have little effect on LDL or HDL cholesterol levels
Found in plants, principally α-linolenic acid (essential fatty acid)

28. 3. Polyunsaturated fats (PUFAs)
Dietary Fats
3. Polyunsaturated fats (PUFAs)
ω-3 Fatty acids
Included in infant formulas to promote brain development
A deficiency of essential fatty acids is characterized by scaly dermatitis, hair loss and poor wound healing
% of total calories recommended

29. Dietary fats and plasma lipids
4. Trans fatty acids
Do not occur naturally in plants but in small amounts in animals
Formed during the hydrogenation of liquid vegetable oils e.g. in the manufacture of margarine and partially hydrogenated vegetable oil
Elevate serum LDL but not HDL

30. High-Fat Foods and Heart Disease

31. High-Fat Foods and Heart Disease

32. Other dietary factors affecting CHD
Dietary Fats
Other dietary factors affecting CHD
Moderate consumption of alcohol (e.g. 2 drinks a day) decreases the risk of CHD, because there is a positive correlation between moderate alcohol consumption and the plasma concentration of HDL
Because of the potential dangers of alcohol abuse, health professionals are reluctant to recommend increased alcohol consumption to their patients
Red wine contains phenolic compounds that inhibit lipoprotein oxidation
These antioxidants are also present in raisins and grape seed

33. Recommended Intakes of Fat
Dietary Guidelines
Diet low in saturated and trans fat
Diet low in cholesterol
20 to 35 percent of daily energy from fat

34. Butter and Margarine Labels Compared
The closer the “partially hydrogenated oils” is to the beginning of the ingredients list, the more trans fat it contains