Diet Diet &&

Cardiovascular Cardiovascular SystemSystem

Objectives

• Importance of fats• Fats and CHD• Different types of dietary Fats• Mediterranean Diet• Dietary factors affecting plasma cholesterol• Recommendations

Fats in the Diet

• A concentrated source of energy (9 kcals/gram)

• Supply essential fatty acids such as linoleic and linolenic acids

• Provide phospholipids for membrane function

• Source of fat-soluble vitamins (A, D, E, K) and help in their absorption

• RDA (gm/day): Total fats: 65, Saturated: 20

• Excessive fat intake can cause–Atherosclerosis/heart disease–Obesity

• Chronic diseases are significantly influenced by the kinds and amounts of nutrients consumed.

risk of CHD: in• Dyslipidemias• Smoking• Obesity• Sedentary

lifestyle.• Male gender• homocystenemia

Dietary lipids most strongly influence the

incidence of CHD

DIETARY DIETARY FAT:FAT:

• In the past dietary recommendations emphasized decreasing the total amount of fat in the diet.

•Research now indicates that the type of fat is more important than the total amount of fat consumed.

•A. Plasma lipids and CHD :Plasma cholesterol may arise from the diet or from endogenous biosynthesis.

1.1. LDL and HDL:LDL and HDL: • Plasma cholesterol level varies in response to the diet.

• total plasma cholesterol levels risk for Coronary heart diseases (CHD).

• High levels of LDL cholesterol risk for CHD.

• High levels of HDL cholesterol risk for CHD.

2. Beneficial effect of lowering plasma 2. Beneficial effect of lowering plasma cholesterol:cholesterol: • Dietary or drug treatment of

hypercholesterolemia decreasing LDL & HDL the risk for cardiovascular events.

• Dietary treatment 10 - 20 % reduction in

plasma lipoprotein concentrations.

• Treatment with ““statinstatin”” drugs 30 - 40 % reduction in plasma cholesterol.

B. Dietary fats and plasma lipids

• Triacylglycerols are quantitatively the most important class of dietary fats.

• The influence of triacylglycerols on blood lipids is determined by :

– The chemical nature of the constituent fatty acids.

– The presence or absence of double bonds (saturated vs. mono- and polyunsaturated).

– The number and location of the double bonds (n-6 vs n-3).– The cis vs trans configuration of the unsaturated fatty

acids.

1. Saturated fat:1. Saturated fat: • Saturated fats are triacylglycerols containing fatty acids

with no double bonds in its side chains.

• Dairy and meat products. • Vegetable oils, such as coconut & palm oils

Sources

• levels of total plasma cholesterol • LDL cholesterol • Risk of CHD.

Limitation of saturated fats intake risk of CHD.

Effects

2. Monounsaturated fats:2. Monounsaturated fats:

• Monounsaturated fats are triacylglycerols containing primarily fatty acids with one double bond.

• Unsaturated fatty acids are generally derived from vegetables and fish.

• When substituted for saturated fatty acids in the diet, monounsaturated fats total plasma cholesterol & LDL total plasma cholesterol & LDL cholesterol and cholesterol and HDLs. HDLs.

• Mediterranean cultures, with diets rich in olive oil (high in monounsaturated oleic acid), show a low incidence of coronary heart disease.

The Mediterranean diet:The Mediterranean diet: • rich in: rich in: - monounsaturated fatty acids (from olive oil) - n-3 fatty acids (from fish oils and some nuts) • low in: low in: - saturated fat.

• The Mediterranean diet serum total cholesterol and LDL serum total cholesterol and LDL • Plasma triacylglycerols are unchanged.

• Seasonally fresh food• Abundance of plant material• Low amounts of red meat• Olive oil as the principal source of fat.

Mediterranean diet contains :

3. Polyunsaturated fats3. Polyunsaturated fats::

• Polyunsaturated fats are triacylglycerols containing primarily triacylglycerols containing primarily fatty acidsfatty acids with more than one double-bond.more than one double-bond.

• The effects of polyunsaturated fatty acids ((PUFAsPUFAs)) on cardiovascular disease is influenced by the location of the

double bonds within the molecule. a. n-6 Fatty acids: (omega 6)

• long-chain, polyunsaturated fatty acids with the first double bond beginning at the sixth carbon atom

Sources• Nuts• Avocados• Olives• Soybeans• Various oils (sesame, cottonseed & corn oil).

plasma cholesterol• LDL• HDL

Effects

The powerful benefits of LDL are only partially offset because of the HDL

a. n-6 Fatty acids …… cont’d

b. n- 3 Fatty acids (omega -3) b. n- 3 Fatty acids (omega -3) • Long-chain, polyunsaturated fatty acids, with the first double first double

bond beginning at the third carbon atombond beginning at the third carbon atom

• suppress cardiac arrhythmias• serum triacylglycerols• tendency to thrombosis• Lowers blood pressure• risk of cardiovascular mortality• little effect on LDL or HDL cholesterol levels.

Effects

• Plants (mainly α-linolenic acid—an essential fatty acid). • Fish oil containing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).

Sources

• Linoleic acid (n-6 )Linoleic acid (n-6 ), and linolenic acidlinolenic acid (n-3 )

are essential fatty acids fluidity of membrane structure and synthesis of eicosanoids .

Deficiency of essential fatty acids

• Scaly dermatitis.• Hair loss.• Poor wound healing

4. Trans fatty4. Trans fatty acids:acids:

• Trans fatty acids are chemically classified as “ unsaturated fatty acids, behaving more like unsaturated fatty acids, behaving more like saturated fatty acids in the bodysaturated fatty acids in the body, i.e. they serum LDL (but not HDL) the risk of CHD ”

• Trans fatty acids do not occur naturally in plants and only occur in small amounts in animals.

• Trans fatty acids are formed during the hydrogenation of liquid vegetable oils, in the manufacture of margarine.

• Trans fatty acids are a major component of many commercial baked goods, such as cookies and cakes, and most deep-fried foods

A key to the presence of trans fatty acids in a food is the words ‘partially hydrogenated’ on the list of package ingredients.

Sources :Animal products: milk, meat, eggs

5. Dietary Cholesterol:

The effect of dietary cholesterol on plasma cholesterol is less important than the amount and types of fatty acids consumed.

Dietary Factors affecting Blood Cholesterol Levels

(I) Factors which increase blood cholesterol1. Dietary cholesterol (play a minor role)2. High fat (enhance intestinal cholesterol absorption 3. Saturated fat: (except 18:0)

- enhance production of LDL and cholesterol - depress LDL uptake- TG high in 18:0 are digested and absorbed more

slowly and less efficiently than those of other fatty acids4. Trans-unsaturated fatty acids: ↑LDL-cholesterol

↓HDL-cholesterol 5. Sucrose, fructose

(II) Factors which decrease blood cholesterol

1. Polyunsaturated fatty acid: eicosanoids (prostaglandin)

2. Omega-3 fatty acid: little effect on LDL( ↓Apo B,↓LDL, VLDL formation,↑VLDL, LDL turn over)

3. Omega-6 fatty acid: ↓LDL-C

4. Plant protein

5. Fiber ( decrease absorption of cholesterol and fat ,increase fecal loss of cholesterol)

Reference

See Dietary Fat : Lippincott pg360