1 CarbohydratesCarbohydrates

2 Carbohydrates Complex Simple Fiber

3 Simple Sugars Monosaccharides: –glucose –fructose –galactose Disaccharides – digestion splits to mono –Sucrose: glucose / fructose –Maltose: glucose / glucose –Lactose: glucose / galactose

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5 Complex CHO (Polysaccharides) CHO consist > 2 single sugar units Starch: long chains of glucose –plant sources Glycogen: branched chains of glucose Cellulose: long chain of glucose –“dietary fiber” –Plant sources

6 Polysaccharides Glucose multiple Glucose Moieties Linked together

7 Dietary Fiber - only in plants Indigestible by human enzymes Soluble oat bran legumes fruit pectin Insoluble Fruit skin vegetables Whole grains Seeds

8 DIGESTION OF CARBOHYDRATES Glycogen, starch and disaccharides (sucrose, lactose and maltose) are hydrolyzed to monosaccharide units in the gastrointestinal tract. The process of digestion starts in the mouth by the salivary enzyme  –amilase. The time for digestion in mouth is limited. Salivary  - amilase is inhibited in stomach due to the action of hydrochloric acid. Another  - amilase is produced in pancreas and is available in the intestine.

9  -amilase hydrolyzes the  -1-4-glycosidic bonds randomly to produce smaller subunits like maltose, dextrines and unbranched oligosaccharides.  -amilase

10 The intestinal juice contains enzymes hydrolyzing disaccharides into monosaccharides (they are produced in the intestinal wall) Sucrase hydrolyses sucrose into glucose and fructose Sucrose sucrase Fructose Glucose

11 Lactose lactase Maltase hydrolyses maltose into two glucose molecules Lactase hydrolyses lactose into glucose and galactose Maltose maltase Galactose Glucose

12 ABSORPTION OF CARBOHYDRATES Only monosaccharides are absorbed The rate of absorption: galactose > glucose > fructose Glucose and galactose from the intestine into endothelial cells are absorbed by secondary active transport Na + Glucose Protein

13 Digestion & Absorption of CHO

Digestible CHO Functions Insulin stimulates cells to absorb glucose Energy: 4 cal / gram Glucose in cell is “metabolized” to: H2O + CO2 + ATP + Heat Sugar alcohols : sorbitol, xylitol energy

Fate of Glucose from Food Some used for immediate energy (ATP) Some stored as glycogen in liver & muscle –Glucose in glycogen is readily available for ATP Excess changed to fat– for storage/reserve of energy

16 Glycogen CHO storage in muscle and liver for quick energy Glycogen glucose

17 Sugar and Health Empty calories Dental caries NOT diabetes NOT hyperactivity

Lactose Intolerance Caused by insufficient enzyme lactase; Undigested and unabsorbed lactose is acted upon by bacteria Symptoms: bloating, flatulence, abdominal pain, diarrhea No need to omit milk, milk products - Lactaid may be added to milk or use lacatase treated milks -use fermented milk products such as yogurt, cheese where most of lactose is already broken down

19 Fiber and Health Insoluble fiber prevents constipation and hemorrhoids Soluble fiber  Blood cholesterol (helps prevent heart disease) Helps control blood glucose levels Excess fiber (>50 g/d)  mineral absorption GI discomfort

20 Current recommendations suggest that adults consume grams of dietary fiber per day, depending on age and gender. Children ages 1 and up should consume at least 19 grams of fiber per day. Yet the average American eats only 15 grams of dietary fiber a day. (See the table below for specific fiber recommendations based on age and gender.)table

21 Diabetes Type 1: Insulin-dependent diabetes mellitus (IDDM); –lack of insulin; destruction of pancreas Type 2: Non insulin-dependent diabetes mellitus (NIDDM); –insufficient production of insulin; insulin resistant; –Western diets and physical inactivity are conducive Gestational diabetes: 3-6% pregnant women; disappears after delivery

22 Carb Sources Starch from grain products & veggies Sugars from fruits & refined sweets Milk sugars from dairy NOT from eggs, meats or oils 55-60% of calories should come from carbs

Artificial Sweeteners Saccahrin Aspartame Sucralose Acesulfame potassium Contain zero calorie

24 Alcohol NOT a “nutrient” Has 7 calories per gram Absorption is rapid from stomach Metabolism (detoxification) by enzymes in liver takes time

Alcohol Facts Benefits (moderate drink,1-2 drinks) Increases HDL-cholesterol Protects against heart disease Adverse effects (excessive drink, > 5 drinks) Hypertension, stroke, liver cirrhosis, cancers, nerve system disorders Associated with: Death from homicide, drowning, traffic accidents, suicide Legal limit: % blood level

26 Typical “drink” has about same amount of alcohol regardless of source

27 RDA for Carbohydrates The RDA for carbohydrates is set as the minimum amount needed to fuel the brain but not an amount adequate to satisfy typical energy needs Most experts recommend that 45% to 65% of total calories come from carbohydrates Added sugars limited to 6-10% of calories g of fiber are recommended daily for adult women and men respectively

28 Blood glucose is the energy source to all cells Ideally, levels between mg/dL (3,3 – 5,5 mmol/l) are needed for homeostasis

29 Glycogen: Carbohydrate energy stored in –1. The liver –2. The muscles Glycogenesis: The process of converting glucose to glycogen Glycogenolysis: Glycogen back to glucose Gluconeogensis: Glucose from fats & protein

30 Glucose-6-phosphate is the central metabolite in the synthesis and decomposition of glycogen. In the well-fed state glucose is converted to glucose-6-phosphate, which is the precursor for the glycogen synthesis. The glucose-6-phosphate derived from the breakdown of glycogen has three fates: (1) glycolysis; (2) pentose-phosphate pathway; (3) convertion to free glucose for transport to another organs.

31 Conversions GLUCOSE GLYCOGEN FAT GLUCOSE GLYCOGEN FAT

32 Conversions

33 Conversions