12.sakina nutritional imp of carbohydrate

© 2010 Pearson Education, Inc.

NUTRITIONAL IMPORTANCE OF CARBOHYDRATE DR SAKINA ,MBBS,M.D

SENIOR LECTURER ,MSU


There are six types of nutrients:

Carbohydrates

Fats

proteins

Vitamins

Minerals

Water

Energy providing

We need energy for all activities. When our body uses carbohydrates, fats, and proteins, energy is released: calories

Energy providing


What Are Carbohydrates? Produced by plants during photosynthesis After eating plant foods, humans convert the carbohydrates

into glucose Glucose

• Most abundant carbohydrate• Preferred source of energy for the blood, brain, and

nervous system Carbohydrate-rich plant foods make up the foundation of

diets all over the world


IMPORTANCE OF CARBOHYDRATE Provide a major fraction of the body’s energy needs Carbohydrate may provide about 60-65%of total calories Carbohydrates also provide fibres Dietary carbohydrate (i) Available carbohydrate these can be metabolised by the

body to give energy (ii)unavailable carbohydrate –these cannot be assimilated

and constitute only dietary fibres


FUNCTIONS OF CARBOHYDRATE Main source of energy: body tissues require a constant

daily supply of CHO in the form of glucose in all metabolic reactions.

Exert a protein sparing action. A person must eat a minimum of 100-125gm/day in order to spare the protein.

Necessary for normal fat metabolism. If there is insufficient CHO, large amount of fat is used for energy, which is dangerous due to release of ketone bodies which can cause acidosis which if prolonged can result in brain damage

Glucose is sole source of energy for the brain


FUNCTIONS OF CARBOHYDRATE

Pentoses are constituents of several compounds eg.nucleic acids

Synthesis of non-essential amino acids

Energy supply for muscle - The muscle glycogen is broken down to lactic acidto provide energy for muscle contraction

Lactose remains in the intestine longer than other dissaccharides and thus encourages the growth of beneficial bacteria. (these bacteria help in synthesis of certain vitamins: B-complex and vit.K)


FUNCTIONS OF CARBOHYDRATE Cellulose and other closely related undigestible CHOs aid

in normal excretion. They stimulate the peristaltic movements of the GI tract and absorb water to give bulk to the intestinal contents.

CHOs are important components of many compounds such as nucleic acids, connective tissues


Carbohydrate –and health Many high sugar foods are a source of empty calories

(foods with calorie but without nutritional value e.g. cakes, cookies, candy and beer , such carbohydrates increase risk of DENTAL CARIES (cavities)

Extra/empty calories from sugar are converted to fat and can contribute to OBESITY

High sugar diets have been shown to alter blood lipid levels linked to - HEART DISEASE


Classification of Carbohydrates Simple carbohydrates

• Monosaccharide• Disaccharide• Perceived as sweeter than complex carbohydrates

- Mixes with saliva and reacts with taste buds Oligosaccharides Complex carbohydrates

• Polysaccharides


Dietary Fiber –complex carbohydrate not digested by human enzymes• Nondigestible polysaccharides• Provides no energy• Classification

- Soluble- Pectins, beta-glucan, some gums, mucilage- Easily fermented by intestinal bacteria

- Insoluble- Cellulose, lignin, some hemicelluloses- Not easily fermented


Fiber Health Benefits Soluble fibers

• Slow gastric emptying and may delay absorption of some nutrients- Helps reduce serum cholesterol- Improve appetite control- Normalize blood glucose levels

• May help protect against colon cancer Insoluble fibers

• Relieves constipation Most plant foods contain both soluble and insoluble fibers


Dietary Fiber

Benefits Helps lower risk of

- Bowel irregularity- Obesity- Heart disease- Cancer- Diabetes mellitus

Adverse effects - Too much fibre depresses the iron,Ca,P,Mg

utilization and increases intestinal flatulence

© 2010 Pearson Education, Inc. Figure 4.12

Dietary Fiber-FUNCTION Chronic constipation can

lead to diverticulosis and diverticulitis

Prevention of constipation and diverticulosis• Insoluble fiber helps

reduce transit time of foods in the colon

• Soluble fiber helps make stool easier to pass by increasing bulk and softening texture

© 2010 Pearson Education, Inc. Figure 4.13

Dietary Fiber Prevention of heart disease and diabetes

• Viscous, soluble fiber helps lower elevated blood cholesterol levels- Interferes with reabsorbtion of bile acid


GLYCEMIC INDEX Assesed by glucose tolerance test (the glycemic

response)after the particular diet & comparing it with a reference meal

The reference meal is always taken as 50gm glucose

Area under the glucose tolerance curve after 50gm test meal ----------------------------------------------------------------- x100

Area under the curve after 50gm of reference meal (glucose)


GLYCEMIC INDEX CURVE


GLYCEMIC INDEX

Food with low GI tends to have high satiety, thus limit caloric intakeFood with high fibre and low GI is recommended by nutritionists


What is the glycemic index?

Glycemic Index (GI)

A scale that ranks carbohydrates by how much they raise blood glucose levels compared to a reference food.


Glycemic Index (GI): Ranking

Low 0 – 55

Moderate 56 – 69

High 70 or more


Glycemic Index (GI): Sample Graphs

Adapted from Good Carbs Bad Carbs Reprinted courtesy of Marlowe & Company.


Factors Influencing GI Ranking

• Type of starch



Type of Starch

• Absorbs less water• Molecules form tight clumps• Slower rate of digestion

• Absorbs more water• Molecules are more open• Faster rate of digestion

Amylose Amylopectin

Lower GI

Kidney beans (28)Uncle Ben’s converted LG rice (50)

Higher GI

Russet potato (85)Glutinous rice (98)



• Type of starch• Physical entrapment



Physical Entrapment

Endosperm

Bran

Germ

Bran acts as a physical barrier that slows down enzymatic activity on the internal starch layer.

Lower GI All Bran (38)

Pumpernickel bread (50)

Higher GI Bagel (72) Corn Flakes

(92)



• Type of starch• Physical entrapment• Viscosity of fiber



Viscosity of FiberViscous, soluble fibers transform

intestinal contents into gel-like matter that slows down enzymatic activity on starch.Lower GI

Apple (40)Rolled oats (51)

Higher GI

Whole wheat bread (73)Cheerios (74)



• Type of starch• Physical entrapment• Viscosity of fiber• Sugar content



Sugar Contentsugar sucrose glucose + fructose

starch maltose glucose + glucose

(GI 60) (GI 100) (GI 19)

(GI 105) (GI 100) (GI 100)

Lower GI

Frosted Flakes (55)Raisin Bran (61)

Higher GI

Golden Grahams (71)Rice Krispies (82)



• Type of starch• Physical entrapment• Viscosity of fiber• Sugar content• Fat and protein content



Fat & Protein ContentFat and protein slow down gastric

emptying, and thus, slows down digestion of starch.Lower GI

Peanut M&M’s (33)Potato chips (54)Special K (69)

Higher GI

Jelly beans (78)Baked potato (85)Corn Flakes (92)



• Type of starch• Physical entrapment• Viscosity of fiber• Sugar content• Fat and protein content• Acid content



Acid ContentAcid slows down gastric emptying, and thus, slows down the digestion of starch.

Lower GI

Sourdough wheat bread (54)

Higher GI

Wonder white bread (73)



• Type of starch• Physical entrapment• Viscosity of fiber• Sugar content• Fat and protein content• Acid content• Food processing



Food ProcessingHighly processed foods require

less digestive processing.

Lower GI

Old fashioned, rolled oats (51)

Higher GI

Quick, 1-minute oats (66)



• Type of starch• Physical entrapment• Viscosity of fiber• Sugar content• Fat and protein content• Acid content• Food processing• Cooking



CookingCooking swells starch molecules and softens foods, which speeds up the rate of digestion.Lower GI

Al dente spaghetti – boiled 10 to 15 minutes (44)

Higher GI

Over-cooked spaghetti – boiled 20 minutes (64)


How does all this affect our glycemic levels?

How does all this make us feel after eating carbohydrate-containing foods?

Type of starch

Physical entrapment

Viscosity of fiber

Sugar contentFat content

Protein content

Acid content

Food processing

Cooking



Glycemic Load (GL): What does it mean?

Glycemic load measures the degree of

glycemic response and insulin demand produced by a specific

amount of a specific food.

Glycemic load reflects both the quality and

the quantity of dietary carbohydrates.

GL = GI/100 x CHO (grams) per serving

Example: GL of an apple = 40/100 x 15g = 6g


Glycemic Load (GL): Ranking

Individual food portion:Low 0-10Moderate 11-19High 20+

Whole day:Low < 80Moderate 100High > 120


GI vs. GL

Glycemic Index: ranks carbohydrates based on

their immediate blood glucose response.

GI = glycemic qualityGlycemic Load: helps predict blood glucose

response to specific amount of specific carbohydrate food.

GL = glycemic

quality

quantity


Benefits of Low GI Diet

Are there any documented benefits to lowering the GI of one’s diet?

YES!BG levels

cholesterol levels

weight

heart disease risk

type 2 DM risk


Caution!

Do not focus exclusively on achieving a low glycemic load diet with all low glycemic index food choices.

Result could be: high fatlow carbohydratelow fibercalorically dense

Instead…


A Better Idea

Aim for a well-balanced diet that includes low glycemic index carbohydrates. Use glycemic load as a guide for controlling portions.Hint: Low GI CHOs allow for larger portions, while regulating the GL.High GI CHOs require smaller portions to regulate the GL.


Thank You!

Health & Medicine

12.sakina nutritional imp of carbohydrate