Lipids

Iva Řehová

• Like carbohydrate, a lipid molecule is composed of

carbon

,

oxygen

, and

hydrogen

atoms linked together in a specific and unique way.

• • • •

There are three different functions for lipids in our bodies: Energy source Energy storage

Forming the

membranes

around our cells.

Hormones and vitamins

(facilitate absorption of fat soluble vitamins (A, D, E and K) and carotenoids) • • The largest amount of energy is stored in the body as fat. Lipids contain a

lot of calories in a small space.

• Fats are stored as

muscle tissue

and

triglycerides adipose

(fat) in both the

tissue

.

• Essentially, a lipid molecule consists of one

glycerol

molecule and three

fatty acid

molecules to form

triglyceride

.

• Fatty acids have two unique characteristics:

1. the length

of their carbon chain

2. the bonding

of carbon atoms

The length of carbon chain:

• • •

Short-chain fatty acids

carbons;

sources

(SFA) have 4 to 8 : milk and dairy produce

Medium-chain fatty acids

(MFA) have 9-12 carbons;

sources

: milk and dairy produce, coconut and palm oil

Long-chain fatty acids

(LFA) have more than 12 carbon;

source

: many animal fats • Oils are usually of the short-variety.

• The fatty acids with shorter chains are more easily breakdown during digestion.

The bonds of carbon chain

•

saturated

fatty acids with only single bonds linking carbons together

H H H H OH R - C C - C - C - C = O

glycerol

H H H H

•

unsaturated

fatty acids with at least one double bonds in the carbon chain

–

monounsaturated

–

polyunsaturated

H H H H H H OH R - C = C - C - C = C - C - C = O

glycerol

H H

• There are different types of fatty acids

in one molecule of triglyceride.

• Regardless of the degree saturation, all lipid have essentially the same number of calories per unit weight.

The American Heart Association has set guidelines for triglyceride levels in blood:

Level

mmol / L

Interpretation Level

mg / dL <150 150-199 200-498 >500 <1.69

1.70-2.25

2.25-5.63

>5.65

Normal range, lowest risk of CVD Borderline high High level, high risk of CVD Very high, increased risk of CVD

Saturated fats

• • At room temperature, saturated fats are usually solid.

Source

: primarily in animal products including beef, lamb, pork and chicken, egg yolk, dairy fats of cream, milk, cheese, butter; coconut and palm oil; non-dairy creams because they contain coconut oil • Consumption of saturated fats has been linked with

risk of coronary heart disease

: – sources of saturated fat are

full of cholesterol

and palm oil) (except coconut – diet high in saturated fat

facilitates cholesterol synthesis

the liver (including coconut and palm oil) by

Unsaturated fats

• At room temperature, unsaturated fats are usually liquid.

• •

Monosaturated Sources

: olive, peanut, canola, rape oil, almonds, avocado • •

Polyunsaturated Sources

: sunflower, soybean, corn, and safflower oil, fish oil, walnuts, sesame seeds, pumpkin seeds, tofu, lard • Unsaturated fatty acids are sensitive to

heat damage

and

light

– store them in the dark bottles and use for cold or short hot preparations

• • Humans and other mammals

can synthesize saturated monounsaturated fatty acids

protein. and

some

from carbon groups in carbohydrate and

Polyunsaturated fatty acids an omega-3

acid are considered

essential fatty acids

synthesized by humans). fatty acid and an

omega-6

(because they cannot be fatty •

Essential fatty acids: omega-3

The parent fatty acid of the omega-3 series is

alpha-linolenic acid (ALA) ALA

- humans can synthesize eicosapentaenoic acid (

EPA

) and docosahexaenoic acid (

DHA

) from ALA

Sources

: flaxseed oil, soybean oil and canola oil, nuts, seafish – salmon, herring, sardine, tuna •

omega-6

The parent fatty acid of the omega-6 series is

linoleic acid (LA).

LA

- humans can synthesize dihomo-gamma-linolenic acid (

DGLA

) and arachidonic acid (

AA

) from LA

Sources

: olive and sunflower oils, sesame, pecans, pine nuts, freshwater fish – carp, trout, catfish, eel

• Clinical signs of

essential fatty acid deficiency

decreased growth in infants and children, increased susceptibility to infection and poor wound healing.

• Omega-6 and omega-3 PUFA are important structural components of cell membranes, they are important to central nervous system function, and they play important roles in vision. • Typical Western diets tend to be much

higher in omega-6 fatty acids than omega-3 fatty acids.

• • It has been estimated that the ratio of omega-6 to omega-3 fatty acids in the diet of early humans was 1:1, but the ratio in the typical Western diet is now almost 10:1 due to increased use of vegetable oils rich in LA and declining fish consumption.

Omega-3

intakes are associated with significant reductions in cardiovascular disease risk, the American Heart Association recommend that all adults eat

fish

, particularly oily fish,

at least twice weekly

.

• A large body of scientific research suggests that increasing the relative abundance of dietary omega-3 fatty acids may have a number of health benefits.

• Increasing EPA and DHA intake may be beneficial to individuals with

diabetes

, especially those with elevated serum triglycerides.

Approximate percentage of fatty acids in common fats and oils canola oil (rapeseed) olive oil soybean oil sunflower oil pork fat (lard) butterfat palm oil coconut oil 0 20 polyunsaturated 40 60 monosaturated 80 saturated 100

Trans-unsaturated fatty acids (TFA)

• • TFA are product of

hydrogenation

saturation of fatty acids within oils and converts natural cis to trans configuration which increases the •

Hydrogenation

shelf life. = industrial process that chemically transforms a low melting point oil into a solid fat with a higher melting point to enhance product taste, stability and • Found in commercially

fried foods

(French fries, popcorn)

, commercial baked goods

and

snacks (

cakes, cookies, biscuits)

, margarine

, and cheap

(not in e.g. Flora, Rama)

.

vegetable shortenings

Trans

-fatty acids have many adverse metabolic effects including

elevation of LDL

cholesterol,

triglycerides

,

reduction in HDL

cholesterol, and adverse effects on

endothelial function, inflammatory markers

, and probably

insulin resistance.

• The diet in northern European countries has traditionally contained more

trans

-fatty acids than the diet in Mediterranean countries in which olive oil is commonly used.

• Mean daily intakes of

trans

-fatty acids in European countries range from

minimal values values

in Italy, Portugal, Greece and Spain to

greater

for Germany, Finland, Denmark, Sweden, France, United Kingdom, Belgium, Norway, the Netherlands, and Iceland.

• Recent

decreases

in the

trans

presumably due to modifications of commercially available fats or changes in consumer choices.

content of the diet have been observed, • Today, most margarines in the European market have a lower content of trans fatty acids than 5 to 10 years ago and in most cases the change has been carried out without adverse effects for the consumer.

• The technologies used here are now implemented in a number of other industries. New technologies have been adopted to solve specific problems in, for example, the bakery and chocolate confectionery.

Cholesterol

• Cholesterol is non-fat substance vital to human metabolism, and although it may be obtained in the diet only from animal foods, the body can produce its own way.

• The recommended cholesterol intake is less then

300 milligrams per day

(the richest source is egg yolk has 220 mg). • A positive relationship has been established between high blood cholesterol levels and coronary heart disease, reduction of dietary cholesterol has been advocated by a number of health recommendations.

• Fruits, vegetables, grains, and nuts have no cholesterol.

Cholesterol content – egg and meat group

Eggs Amount Cholesterol (mg] 1 Liver, kidney, brains 1 oz 220 120 Shrimp Beef, pork, ham Poultry Fish 1 oz 1 oz 1 oz 1 oz 45 25 23 21

Cholesterol content – milk group

Ice cream Milk, whole Milk, 2% Milk, skim Cream cheese Butter Amount 1 cup 1 cup 1 cup 1 cup 1 tbsp 1 tbsp Cholesterol (mg] 85 27 15 7 18 12

Type of Fat Saturated Fat Trans Fats Monounsaturated Fats Polyunsaturated Fats : Omega-6 Dietary Sources Red meat, cheese, butter, commercially fried foods and baked goods Commercially fried foods and commercially prepared snacks and baked goods Nuts, olives, avocados, olive & canola oils Corn, soybean and safflower margarine & oils Total Cholesterol Increase Increase Decrease Decrease Omega-3 Salmon, mackerel, herring, flaxseed, walnuts, walnut oil, soybean and soybean oil Decrease LDL cholesterol HDL cholesterol Triglycerides Increase Increase Decrease Decrease Decrease No effect Slight Decrease No effect Decrease No effect No effect No effect No effect Unknown Decrease •Recommendation is that total

daily energy

intake

daily fat intake

be limited to <

30% of total

•with no more than

10%

provided by

saturated and trans fats,

•

polyunsaturated

fatty acids should be limited to no more than

10%

of total daily energy intake ( Because polyunsaturated fatty acids may also lower HDL cholesterol as well as LDL-cholesterol) •

10%

provided by

monounsaturated

fats

Digestion and absorption

• Digestion of fats starts in the

stomach

by the action of

linqual lipase

, an enzyme

secreted in the mouth.

This enzyme digests short- and medium-chain saturated fatty acids.

• • The

stomach

secretes

gastric lipase

which works with linqual lipase to digest a very small amount of fat.

The major breakdown of lipid occurs in the small intestine

.

• The fat is

emulsified bile

into very small droplets by the action of (secreted from gallbladder) - it facilitates enzyme action.

•

Pancreatic lipase

, the main fat-digesting enzyme, degrades some of the triglyceride molecules to monoglycerides and fatty acids.

• In this simpler form,

monoglycerides absorbed by the intestine

.

are more easily • The absorbed glycerol, fatty acid, and monoglyceride molecules are then free to recombine to

reform triglycerides

.

• The fatty acids take one of two routes depending on their chain length:

–

Short-

and

medium-chain

fatty acids proceed to the portal vein and empty into the

liver

.

–

Long-chain

fatty acids and first reconverted to a

cholesterol chylomicron

is and then transported through the lymphatic system into the systemic vein that empty into the heart.