Four Groups of Macromolecules:

Four Groups of Macromolecules:

Recently the FDA gave its approval to Proctor and Gamble to use a controversial fat replacement in snack foods. What makes olestra unique is that it is not just a fat substitute, but it is a fat. It has all of the same properties of fat when it is used in cooking, but the body can not absorb it so it has no calories. At first glance, olestra sounds like the answer to the prayers of many dieters'. However, there are some serious pro's and con's that go with this story. Proctor and Gamble began developing and studying olestra 25 years ago. To date the company has spent a reported $200 million testing the product. Originally, the intent was to have olestra approved for use in many products, but the scope had to be narrowed to quicken the approval process. The company plans to use olestra in Pringles chips. It is estimated that the approval of olestra will generate an annual market of one billion dollars within the next ten years.

The Pro's:• products taste very similar to the real thing • zero calories • no fat absorbed by the body • non- toxic

The Con's: The arguments against olestra are strong as well. One less than pleasant side effect is diarrhea and in some individuals, something called "anal leakage". The Diarrhea is caused by the chemical structure of olestra. It is a large molecule with fatty acids packed very close together. The body's enzymes can not break down the fat and the molecule passes through the intestine unabsorbed.

http://www.cheshire-med.com/services/dietary/nutrinew/olest.html

2. LIPIDS, the fats of life

• Fats, oils, cholesterol, hormones• Composed of C,H,O (and P for phospholipids)

but not water soluble• Store the most energy (9 kcal/g)

Three types of lipids

a. Triglycerides

b. Phospholipids

c. Sterols

a) TRIGLYCERIDES

• Most common fat in plants and animals, used in storage (9 kcal/g)

• A molecule of 3 fatty acids attached to a glycerol backbone:

fatty acid

fatty acid

fatty acid

• Fatty Acids are long hydrocarbon chains– Most are 4-24 carbons

long• Always an even

number of carbons– Carbon chains differ in:

• Length• Points of

unsaturation

There are two types of fatty acids:

i) Saturated fatty acids -have single C-C bonds

(saturated with hydrogen)

- form straight chains

• Triglycerides with primarily saturated fatty acids:– Solid – Primarily from animal sources

• Plant sources include palm and coconut oil

– More stable than triglycerides with unsaturated FA

• Store better• Taste better!• Associated with health risks

• Food Sources with saturated fats– Butter, cream, milk,

cheese– Red meat– Chicken and fish are a

mixture of saturated and unsaturated fats

ii) Unsaturated fatty acids-have double C-C bonds-form bent/kinked chains- Can be mono or pol-

unsaturated

• Triglycerides with primarily unsaturated fatty acids are:– Liquids (oils)– Primarily from plant

sources– Double bonds are

reactive• Therefore plant oils react

with oxygen and go rancid easily

• Sources of Unsaturated Fats– Monounsaturated

• Olive oil, canola oil, peanut oil

– Polyunsaturated• Corn oil, soybean oil,

sunflower oil…..

• Unsaturated fats can be turned into saturated fats through hydrogenation– adds hydrogens to double bonds– Removes “kinks” from fatty acid chains

• Fully hydrogenated fats have the same health issues as natural sources of saturated fats

• Partially hydrogenated triglycerides– Often the remaining

double bonds converted from cis to trans form

• Cis form is the naturally occurring form

• Trans fatty acids are associated with health risks

Cis and Trans Fatty acids

• Essential Fatty Acids – Omega-3 FA => double

bond 3 C from the end • May lower cholesterol and

risk of heart disease, hypertension, ?cancer, ?arthritis

• Good food sources: fish, soy, nuts, many oils

b) PHOSPHOLIPIDS

-structural components of cell membrane

hydrophobic tailhydrophilic phosphate head

• Structure of a phospholipid:–Glycerol backbone (3 carbons) with 2

fatty acids attached and one phosphate group

–Attached to the phosphate group is some other group

Some cool things you can do with lipids…

c) STEROLS• 4 linked carbon rings with side

chains• natural components of cell

membranes• used by cells to make steroid

hormones, vitamin D, bile salt

testosterone

progesterone

cholesterol

• if there is too much, cholesterol can close arteries, depriving tissue of nutrients and leading to stroke

• There are two types of cholesterol: LDL and HDL– Lipids don’t dissolve well in water (duh…) so for

them to get around the blood stream they bind to proteins and make lipoproteins

• LDL: low density lipoprotein• HDL: high density lipoprotein

good cholesterol vs. bad cholesterol

Cholesterol and blood do not mix well. So, for cholesterol to travel through your blood, it is coated with a layer of protein to make lipoprotein

• You want to have low LDL (low density lipoprotein) and high HDL (high density lipoprotein

• LDL– “Bad” cholesterol– Contributes to plaques

when cholesterol “falls off” the LDL and is deposited on artery walls

– Plaques narrow arteries• Raises blood pressure• Increases risk of blood

clots and heart attacks

• HDL– High density lipoprotein– HDL transports cholesterol and other lipids

back to liver for disposal• Can pick up cholesterol from plaques• Good cholesterol

• Recommended levels of fat intake:– 20-35 % daily kcal from

fats (triglycerides)• Maximum 10% from

saturated fats

– Maximum 300 mg cholesterol per day• No or lower

cholesterol intake is fine/good

Cholesterol

• Maximum level of intake recommended– 300 mg/day– Make all we need, so no

intake is fine• Food Sources – all

animal (no plant sources)– Egg yolk– Dairy (unless fat removed as

in skim milk)– Meat, poultry

Lowering Cholesterol Levels1. Reduce intake of:

• Saturated fats• Trans fatty acids• Cholesterol• Sugars (if sugar

sensitive)2. Increase intake of:

• soluble fibers (oats and legumes)

• fish

Lowering Cholesterol Levels

3. Moderate alcohol intake

4. Exercise – aerobic may be best

5. Lose weight