1. DIGESTION & ABSORPTION OF CARBOHYDRATES AND THEIR DISORDERS
Dr Sara Mariyum

2. Nutrition
It is a process by which organisms obtain and utilize their food
It has two parts:
1. Ingestion- process of taking food into the digestive system so that it may be hydrolyzed or digested.
2. Digestion- the breakdown of food (either chemically or mechanically) in order to utilize nutrients

3. Nutrients Micronutrients- vitamins, minerals, & water
Macronutrients- proteins, lipids, carbohydrates

4. Water, vitamins, and minerals are small molecules that can be absorbed without digestion. (Hydrolysis)
Large molecules like carbohydrates (starch), lipids, and proteins require digestion.

5. Digestion
Digestion – The process of changing food into simple components that can be absorbed by the body.
Digestive tract or Gastrointestinal tract- where digestion & absorption take place
Mouth->esophagus->stomach->small intestine->large intestine

6. Types of Digestion
Chemical Digestion
Mechanical (Physical) Digestion

7. Mechanical Digestion
Food is crushed, broken or cut into smaller pieces (ingestion into MOUTH)
It INCREASES the surface area of the food in order to aid in chemical digestion
Is accomplished by PERISTALSIS and by the churning of the stomach.

8. Chemical Digestion Is carried out by the digestive ENZYMES
Example: Saliva -breaks down starch into disaccharides (contains the enzyme amylase)
Stomach acid (HCL or Hydrochloric Acid) - breaks down gastric protease which digests proteins
BILE -produced by the liver and stored in the gall bladder breaks down fats

9. MECHANISM FOR CHEMICAL DIGESTION
Hydrolysis - the splitting of large, insoluble molecules into small, soluble molecules with the addition of water

10. This process is regulated by hydrolytic (digestive) enzymes and is illustrated by the following:
1. Maltose + water ----> simple sugars (glucose)
2. Proteins + water ---> amino acids
3. Lipids + water ---> 3 fatty acids + glycerol

11. Carbohydrates
Carbohydrates are made of carbon, hydrogen and oxygen atoms.
These atoms form chemical bonds that follow the laws of nature.

12. Digestion of Carbohydrates
Monosaccharides
Do not need hydrolysis before absorption
Di- and poly-saccharides
Relatively large molecules
Must be hydrolyzed prior to absorption
Hydrolyzed to monosaccharides
Only monosaccharides can be absorbed

13. Carbohydrates Ingestion
Polysaccharides (starch and dextrin's)
Disaccharides ( lactose, sucrose, maltose, trehalose)
Monosaccharide's ( glucose and fructose)

14. Starch

15. Carbohydrate Digestion
Mouth
Salivary amylase
Breaks starches down to maltose, maltotriose, alpha dextrins
Plays only a small role in breakdown because
of the short time food is in the mouth

16. Carbohydrate Digestion
Pancreas
Pancreatic amylase
Hydrolyzes alpha 1-4 linkages
Produces monosaccharides, disaccharides
and oligosaccharides
Major importance in hydrolyzing starch to maltose
Amylase
Polysaccharides
Disaccharides

17. Act on uncooked starch too
Intestinal amylase

19. Digestion in Small Intestine
Digestion mediated by enzymes synthesized by cells lining the small intestine (brush border)
Brush Border Enzymes
Disaccharides
Monosaccharides

20. Digestion in Small Intestine
Sucrase
Sucrose
Glucose + Fructose
Maltase
Maltose
Glucose + Glucose
Lactase
Lactose
Glucose + Galactose

21. Isomaltose isomaltase 2 mol of glucose
Maltotriose maltase 3 mol of glucose
Alpha dextrins maltase n mol of glucose

22. Resistant starch Small intestine….colon Fermentation by bacteria
Form short chain fatty acids

23. Food Containing Resistant Starch
Oats
Cooked and Cooled Rice
Legumes
 Potato Starch.
Cooked and Cooled Potatoes
Green Bananas
Hi-Maize Flour

24. CELLULOSE
No digestive enzyme

25. Sources of Monosaccharide in Small Intestine
Diet
Hydrolysis of Starch
Hydrolysis of Disaccharides

26. Overview Carbohydrate Digestion
Location Enzymes Form of Dietary CHO
Mouth Salivary Amylase Starch Maltose Sucrose Lactose
Stomach (amylase from saliva) Dextrin→Maltose
Small Intestine Pancreatic Amylase Maltose
Brush Border Enzymes Glucose Fructose Galactose
Glucose Glucose Glucose
Large Intestine None Bacterial Microflora Ferment Cellulose

27. Absorption & Transport
Absorption occurs in the small intestine
1. Wall of small intestine covered
with 100s of folds
2. Each fold covered with 1000s of
villi
3. Each villi contains 100s of microvilli

28. Nutrient Absorption - Carbohydrate
Transport for glucose and galactose
Sodium-glucose transporter 1 (SGLT1)
Glucose transporter (GLUT 2)

30. Facilitated transport for fructose
GLUT 5
GLUT 2

33. Distributed to tissue through circulation
Small Intestine
Monosaccharides
Carbohydrates
Portal Vein
Active Transport
Liver
Distributed to tissue through circulation

34. In the liver, galactose and fructose are converted to glucose.
Monosaccharides, the end products of carbohydrate digestion, enter the capillaries of the intestinal villi.
Small intestine
In the liver, galactose and fructose are converted to glucose.
Figure 4.11: Absorption of Monosaccharides.
Monosaccharides travel to the liver via the portal vein.

35. Factor Affecting Glucose Absorption
Intestinal factors
Thyroid
Adrenal cortex
Vitamins

36. Summary of Carbohydrate Digestion and Absorption
Polysaccharides broken down to monosaccharides
Monosaccharides taken up by active transport or facilitated diffusion and carried to liver

38. Lactose Intolerance
Inability to digest significant amounts of lactose, which is the predominant sugar in milk
A result of lactase insufficiency, the enzyme essential for the conversion of lactose into glucose and galactose

39. Types of Lactose Intolerance
Congenital: Absence from birth of lactase due to a mutation in the gene responsible for creating lactase.
Secondary: Due to diseases that destroy the lining of the small intestine along with the lactase.
Developmental: A decrease in the amount of lactase that occurs after childhood and persists into adulthood
Of the three types of lactose intolerance, secondary is the type observed most often in infants participating in the WIC program. Congenital lactose intolerance in infants is very rare. Primary lactose intolerance usually develops after two years of age. Secondary lactose intolerance is usually temporary, perhaps due to illness, and resolves within one to two weeks.

41. Symptoms of lactose intolerance
Intolerance does not involve the immune system
Nausea, cramping, bloating, abdominal pain, gas, diarrhea
Symptoms may begin from 15 minutes to several hours after eating food with lactose
For both children and adults, if your body reacts to food, you may have a food intolerance – not an allergy. Unlike food allergies, food intolerances usually don’t involve the immune system. However, they prompt many of the same symptoms and are often mislabeled as allergies. In persons with lactose intolerance, undigested lactose produces uncomfortable symptoms. Most common are nausea, cramping, bloating, abdominal pain, gas and diarrhea. Symptoms may begin anytime from 15 minutes up to several hours after consuming foods or drinks containing lactose. The severity of symptoms varies from person to person and how much and when lactose is consumed in relation to other foods.

42. Infants with lactose intolerance
Breastfeeding
Alternatives to breastfeeding
Lactose free formula
Most infants produce the lactase enzyme to digest lactose from birth. The body may produce less lactase as it gets older. For the formula fed infant sensitive to lactose, a soy or lactose free formula is most appropriate.

43. Children and Women with Lactose Intolerance
Eat or drink small servings
Eliminating milk and other dairy foods may lead to nutritional risks

44. Glucose Galactose Malabsorption
Congenital defect
Lack of transporter
Diarrhea