Download - 12.sakina nutritional imp of carbohydrate
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NUTRITIONAL IMPORTANCE OF CARBOHYDRATE DR SAKINA ,MBBS,M.D
SENIOR LECTURER ,MSU
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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
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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
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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
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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
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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)
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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
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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
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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
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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
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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
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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
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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
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Dietary Fiber Prevention of heart disease and diabetes
• Viscous, soluble fiber helps lower elevated blood cholesterol levels- Interferes with reabsorbtion of bile acid
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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)
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GLYCEMIC INDEX CURVE
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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
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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.
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Glycemic Index (GI): Ranking
Low 0 – 55
Moderate 56 – 69
High 70 or more
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Glycemic Index (GI): Sample Graphs
Adapted from Good Carbs Bad Carbs Reprinted courtesy of Marlowe & Company.
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Factors Influencing GI Ranking
• Type of starch
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Factors Influencing GI Ranking
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)
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Factors Influencing GI Ranking
• Type of starch• Physical entrapment
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Factors Influencing GI Ranking
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)
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Factors Influencing GI Ranking
• Type of starch• Physical entrapment• Viscosity of fiber
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Factors Influencing GI Ranking
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)
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Factors Influencing GI Ranking
• Type of starch• Physical entrapment• Viscosity of fiber• Sugar content
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Factors Influencing GI Ranking
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)
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Factors Influencing GI Ranking
• Type of starch• Physical entrapment• Viscosity of fiber• Sugar content• Fat and protein content
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Factors Influencing GI Ranking
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)
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Factors Influencing GI Ranking
• Type of starch• Physical entrapment• Viscosity of fiber• Sugar content• Fat and protein content• Acid content
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Factors Influencing GI Ranking
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)
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Factors Influencing GI Ranking
• Type of starch• Physical entrapment• Viscosity of fiber• Sugar content• Fat and protein content• Acid content• Food processing
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Factors Influencing GI Ranking
Food ProcessingHighly processed foods require
less digestive processing.
Lower GI
Old fashioned, rolled oats (51)
Higher GI
Quick, 1-minute oats (66)
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Factors Influencing GI Ranking
• Type of starch• Physical entrapment• Viscosity of fiber• Sugar content• Fat and protein content• Acid content• Food processing• Cooking
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Factors Influencing GI Ranking
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)
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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
Factors Influencing GI Ranking
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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
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Glycemic Load (GL): Ranking
Individual food portion:Low 0-10Moderate 11-19High 20+
Whole day:Low < 80Moderate 100High > 120
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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
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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
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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…
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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.
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Thank You!