Hydrogenation

 Hydrogenation

If an unsaturated vegetable fat is altered by adding hydrogen atoms, which did not exist in nature, the fat molecule is said to be "hydrogenated." 

Hydrogenation transforms the shape of a fatty acid to a "trans" form. 

This molecule does not occur in nature, and the body has difficulty digesting it

This is the problem with margarine — it contains hydrogenated, trans-fatty acids. 

Studies show this type of molecule to be more associated with artery disease than the saturated ("hard") fat found in butter. 

hydrogenated fat also is commonly associated with junk food: potato chips. cookies, etc. 

It is very hard to digest and is strongly associated with vascular disease. 

Trans Fatty Acids

Naturally present in small amounts (<1% of total calories) in animal food sources, including human milk

Mainly introduced in the food chain by the industrial process of hydrogenation

This process is used to make oils solid at room temperature( margarine)

 Triglycerides

A fat molecule is composed of three fatty acid molecules, sixteen to eighteen carbons long, bound to each carbon of the three-carbon-long glycerol molecule. 

It is in the fatty acid chains where saturation, mono unsaturation, poly unsaturation, and hydrogenation occur

Three fatty acids combine with a glycerol molecule to form triglyceride. 

A triglyceride may be solid (fat) or liquid (oil) at room temperature depending on the degree of saturation of fatty acids and length of carbon chain of the fatty acids constituting 

Cholesterol:  It is a fat like lipid that normally occurs in the blood and all cell membranes. It is a major part of brain and nerve tissues. Cholesterol is necessary for normal body function as structural material components of cell membrane in body cells, and in the production of bile acids, vitamin D and sterol/sex hormones.

Some cholesterol is supplied by food, and the body can synthesizes some. 

Average levels of dietary cholesterol are 305mg/day for woman and 440mg/day for men. 

The body synthesizes several time this amount

Heredity, diet, exercise, and other conditions affect   blood cholesterol levels. 

Persons with high blood cholesterol levels appear to be more likely to develop atherosclerosis

RECOMMENDED INTAKE OF FATTY ACIDS

ADULTS: The fat content of the diet should be reduced to 35% of energy, unsaturated fatty acids should be increased and saturated fatty acids should provide only 10% of food energy. Tran’s fatty acids should not contribute more than 2% of total fat intake.

Babies: The linoleic acid content of milk lipids varies in amount (3–12%), depending on maternal dietary intake and possibly smoking habit. α-Linolenic acid makes up 0.4% of human milk. 

Infant formula feeds do not always meet these requirements

Lipoproteins

These are compound lipids that contain both protein and various types and amounts of lipids. 

They are 25-30 % proteins and the remaining as lipids. 

They are made mostly in the liver and are used to transport water insoluble lipids throughout the blood, soluble fat protein complexes

 High-density lipoprotein(HDL): Transports lipids from tissues to the liver and decreases the risk of Chronic degenerative diseases 

Low-density lipoprotein(LDL): Transports lipids from the liver to the tissues  and increases the risk of Chronic degenerative diseases

Consumption of Saturated fats increases LDL level, while= increases risk factor for CHD and other chronic non communicable diseases

Consumption of PUFAs and MUFAs increase the level of HDL = Protective effect form CHD and other chronic non communicable diseases

Desirable Blood Lipid Levels

Total Cholesterol         < 200

Triglycerides            < 150

LDL                        < 100

HDL                > 40 Male

                        > 50 Female

Elevated Blood Lipid Levels (Hyperlipidemia) = increased risk for CHD, Hypertension, Stroke, MI

FAT

Most of the body fat (99 per cent) in the adipose tissue is in the form of triglycerides, in normal human subjects, adipose tissue constitutes between 10 and 15 per cent of body weight. 

One kilogram of adipose tissue corresponds to 7700 kcal of energy.

Fats and Other Lipids

Classification

Nutritionally important lipids are classified into 3 main groups on the basis of their Chemical structure.

1.Simple lipids  - include fats and oils (Triglycerides)

2.Compound lipids - includes Phospholipids, lipoprotein

3.Derived lipid  - includes fatty acids and sterols.

Some authorities classify lipids as structural lipids (Phospholipids), Metabolic lipids (fatty acids, lipoproteins and sterols) and storage lipids (triglycerides). 

WHY DO WE NEED FAT TO SURVIVE?

Although fats have received a bad reputation for causing weight gain, some fat is essential for survival. We need this amount of fat for:

• Normal growth and development 

•   20% - 35% of calories should come from fat

• Energy (fat is the most concentrated source of energy) 

• Serve as a vehicle for the absorption of lipid soluble vitamins ( like vitamins A, D, E, K, and carotenoids) 

• Providing cushioning for the organs 

• Maintaining cell membranes 

• Providing taste, consistency, and stability to foods 

• Energy storage, mobilization, and utilization

• Prostaglandin, cytokine synthesis

• Cell differentiation and growth

• Cell membrane structure, myelination

• Hormone synthesis

• Bile acid synthesis

Fatty Acids Classification 

Based on the Length of Carbon chain 

a.Short chain -  2-4 carbon atoms (eg. Butyric acid)

b.Medium chain - 6-12 carbon atoms (Caprillic acid)

c.Long chain - 14-18 carbon atoms (palmitic acid, stearic acid)

d. Extra long chain -   more than 20 carbon atoms (Arachidonicacid)

Based Degree of Saturation

Saturated FA: - The degree of saturation refers to the  number of double bonds between carbon atoms. If all of the carbon atoms in a fatty acid are “saturated” with all hydrogen atoms they can hold, no double bond can exists.

. 

All short or medium chain fatty acids are saturated.  Long chain fatty acids may be either saturated or unsaturated. 

The major saturated fatty acids are palmitic and stearic acids.

Monounsaturated FA: - Monounsaturated fatty acids contain only one double bond between carbon atoms. The most prevalent MUFA in the diet is oleic acid.

 

Polyunsaturated FA (PUFA):- 

They have two or more double bonds between carbon atoms. In omega 3– PUFA, the first double bond occurs 3 carbon atoms from the methyl carbon. 

Important omega-3 fatty acids in nutrition are: 

A.α-linolenic acid (ALA), 

B.eicosapentaenoic acid (EPA), and

C.docosahexaenoic acid (DHA)

Essential fatty acids

• Humans cannot synthesize double bonds within the last nine carbons of the methyl end (n) of any fatty acid chain.

• Fatty acids with double bonds in those locations must therefore come from the diet—and are considered essential

The two essential fatty acids are:

• Linoleic acid (omega 6 fatty acid)

• Alpha-linolenicacids (ALA) (Omega 3 fatty acid) 

Both are (poly)unsaturated

Therefore, absolute requirements for fat in the diet applies only to unsaturated fat