NUTRITIONAL IMPORTANCE OF LIPIDS

2. NUTRITIONAL IMPORTANCE OF LIPIDS

3. What are Lipids ? • Lipids may be defined as organic compounds which are relatively insoluble in water, but freely soluble in non polar organic solvents like: C6H6, CHCl3, Ether, hot alcohol, acetone, etc . • Lipids constitute a heterogeneous group of compounds of biochemical importance.

4. The Food Pyramid

5. Well Known Function • Fats add taste and palatability to food and is the favored cooking medium all over the world. • Fats act as a concentrated source and store of energy

6. Other Functions of Lipids • Structural components of bio-membrane (phospholipids and cholesterol • Provide insulation against changes in external temperature (subcutaneous fat) • Give shape and contour to the body • Protect internal organs by providing a cushioning effect (pads of fat)

7. Act as metabolic regulators (steroid hormones and prostaglandins) • Act as surfactants, detergents and emulsifying agents. (Bile salts) • Act as electric insulators in neurons (Mylen Sheath) • Help in absorption of fat soluble vitamin. (ADEK)

8. Types of dietary fat • Visible fat e.g. butter, ghee and oils • Invisible fat or fat present as part of other food items e.g. egg, fish, meat, cereals, nuts and oil seeds. • Even cereals contain 1 g of fat per 100 g. • We take more than half of essential fatty acid in the form of invisible fat.

9. Animal fat is predominantly saturated, e.g. butter, fat present in meat, chicken, etc.

10. RDA FOR VISIBLE FAT • ADULTS 20 g/day (10% of Caloric Requirement) • In pregnancy 30 g/day • During lactation 45 g/day

11. Dietary sources of Fatty Acids • A significant fraction of FA ingested is contributed by either long chain saturated fatty acids (SFA) e.g. palmitic and stearic. or • Mono unsaturated fatty acids (MUFAs) e.g. (oleic and palimitoleic)

12. An exception • Coconut oil is predominantly composed of medium chain saturated fatty acids (MC-SFA) (lauric and myristic acids) .

13. Poly Unsaturated Fatty Acids (PUFAs) • These are present in vegetable oils and fish oils . • They belong to essential fatty acids. • The omega-3 fatty acids from fish oils decrease the plasma lipoproteins, (VLDL and LDL) and thereby decrease the risk of coronary artery disease.

14. Fish oil is good for the heart – Proven benefits • Reduces triglycerides - 24-27% • Reduces risk markers – C – reactive protein (CRP) • Improves healthy blood flow - key to good heart health • Improves heart related health outcomes • Excellent safety profile

15. Fish oil is a natural source of Omega-3 essential fatty acids • Omega-3 fats are: • Essential fats, healthful fats • Required by humans, we cannot make them • Humans must consume them through diet

16. Consuming enough omega-3s improves • Cellular function • Normal metabolism • Immune activity

17. Sources of PUFA, their Chemical Nature

18. Trans-fatty acids (TFA) are present in dairy products • It is widely used in food industry, since it increases the shelf life of fried food. • Cooking media containing PUFAs and fast food preparations have a high content of trans-fatty acids.

19. Calories intake from fats • In developed countries, calories derived from fats may be as high as 40%, and in developing countries much less, around 10%. • In some parts of Pakistan specially hilly and rural areas fat intake is higher

20. Importance in diet • A minimum intake of lipids is essential to meet the requirements of fat soluble vitamins and essential fatty acids .

21. Important Tips • Vegetables, cereals and pulses do not contain cholesterol. • Vegetable sterols will rather inhibit cholesterol absorption.

22. Cholesterol Content of Food Items

23. Cholesterol and Heart Diseases • The atherogenic effect of cholesterol and the risk at coronary artery disease in people with hyper-cholesterolemia is a well documented fact.

24. Cholesterol and Heart Diseases • It is generally advised that: • Dietary intake should be restricted. • Food items known to be rich in cholesterol (egg yolk, liver, brain, kidney) are to be consumed in limited amounts by normal persons. • Or totally avoided by people at risk.

25. Important Tips • SFraise serum cholesterol while USF (vegetable oils and fish oils) lower it and therefore should be preferred. • High fiber content also reduces serum cholesterol, lowers LDL fraction and raises HDL fraction. • Whole cereals, pulses, leafy vegetables and fruits contain good quantity of fiber.

26. Excess of PUFA • Anything in excess is deleterious. • Excess PUFA may lead to production of free radicals that may be injurious to the cell. • PUFA should not be more than 30% of total fat. • It is essential to take saturated, mono unsaturated and poly unsaturated fatty acids.

27. Recommended Daily Intake of Fat • The ideal fat intake is about 15-20% of total calories, out of which about 25-30% may be from PUFAs. • This will be a total of about 20-25 g of oils and about 3 g of PUFAs for a normal person.

28. Moreover, the fat content should be such that SFA : MUFAs : PUFAs may be in 1:1:1 ratio SFA = saturated fatty acid MUFA = mono unsaturated fatty acid PUFA = poly unsaturated fatty acid) FFA = Free Fatty Acid FA = Fatty acid • Further, cholesterol intake should be less than 250 mg/day.

29. Cooking Medium of Choice • Vegetable oils is the best which will provide PUFA (both omega 3 and omega 6), MUFA and SFA. • Keep intake of animal fat , including butter, as low as possible.

30. Relative Proportions of Fatty acids in oils

31. Clinical Applications • Excessive fat deposits cause obesity. • Truncal obesity is an important risk factor for heart attack. • Abnormality in cholesterol and lipoprotein metabolism leads to atherosclerosis and CVDs. • In diabetes mellitus, the metabolisms of fatty acids and lipoproteins are deranged, leading to ketosis

32. Role of essential fatty acids • Formation of Phospholipids / biomembrane. • As precursors of prostaglandins and leukotrienes • For esterification and excretion of cholesterol

33. Actions and Clinical Applications • The effects of prostaglandins on different tissues are different

34. Effects on CVS • Prostacyclin PGlz is synthesized by the vascular endothelium and its major effect is vasodilatation. • It also inhibits platelet aggregation and has a protective effect on vessel wall against deposition of platelets. • But any injury to the vessel wall would inhibit PGlz synthesis so that platelet aggregation occurs to promote thrombus formation.

35. Inhibitors of the production of vasodilator. PGs are used for inducing the closure of ductus arterisus and surgery may be avoided. • Thromboxane (TXAz) is the main PG produced by platelets. • The major effects are vasoconstriction and platelet aggregation. • Prostacyclin and thromboxane are opposing in activity Prostaglandins lower the blood pressure.

36. Effects on Ovary and Uterus • PGF2 stimulates the uterine muscles. Hence, PGF2 may be used for medical termination of pregnancy. • Is used for induction of labor and arresting postpartum hemorrhage. • PGs are involved in LH-induced ovulation.

37. LT are the most potent chemo-tactic agent (factor attracting cells to the inflammatory site).

38. Major Effects of PG and LT • Prostaglandin E2 decreases lipolysis • increases calcium mobilization from bone • glycogen synthesis. • PGs in general inhibit gastric secretion • increase intestinal motility.

39. They slow down reacting substance of anaphylaxis • They cause smooth muscle contraction • Constrict the bronchioles • Increase capillary permeability and • Produce vasoconstriction.