Essentials of Nutrition for Sports

The structure of a saturated, an unsaturated, and a

trans

unsaturated chemical bond is depicted in

Table 12

and in

Figure 14

.

H

H

|^

|

• C


• C–
  |

|

H

H

H

H

|

|

• C =

C –

H

|

• C =

C –

|

H

Saturated Fat Carbon-Carbon

Single-bond hydrogens

Cis

Fat

Carbon-Carbon

Double-bond hydrogens on

same side

Trans

Fat

Carbon-Carbon

Double-bond hydrogens on

opposite sides

Table 12. Depiction of saturated,

cis

-unsaturated, and

trans-

unsaturated fats. RED hydrogens are on the same side of a

cis

-double

bond and on the opposite sides of a

trans

-double bond.

Cis

-fats are bent. This bending causes the molecule to occupy

more space and become more fluid. This is illustrated in

Figure 14

.

Cis

fat

Trans fat

Figure 14.

Cis

fats are bent.

Trans

fats are generally straight.

Dietary Fat

Fat tastes good to most of us—it makes carbohydrate more

palatable. Fat is also relatively inexpensive.

A small amount of fat is necessary in the diet. Diets that derive more than 30% of their calories from fat are

considered unhealthy, because exces

s dietary fat is associated with

obesity, heart disease, stroke, and some cancers.

Polyunsaturated fats are believed

to be better for health than

saturated or hydrogenated fats. Diets

that derive more than 10% of

their calories from saturated fat are considered unhealthy.

US fat consumption averages about 33% of total calories. Excess fat is much more of a public health problem than too

little.

Requirements

Dietary fat is composed of triglycerides, phospholipids, sterols,

and other lipid-soluble components.

Triglycerides are the major component of dietary fats. Triglycerides consist of a glycerol backbone and three fatty acid

chains, the latter of which are classified as saturated,

cis

• 
  

monounsaturated,

cis

-polyunsaturated, and

trans

-fatty acids.

Monounsaturated fatty acids, saturated fatty acids, and

cholesterol can be synthesized by the body. They are not essential in the diet.

Two polyunsaturated fatty acids are essential in the diet: linoleic

acid and alpha-linolenic acid.

Eicosapentaenoic acid and docosahexaenoic acid, two fatty acids

derived from the elongation and desatur

ation of alpha-linolenic acid,

are also of nutritional significance. Eicosapentaenoic acid and docosahexaenoic acid can be interconverted.

Nutrition for Sports, Essentials of 77