1. CARBOHYDRATES

2. The term “carbohydrate” refers to a group of molecules composed of carbon, hydrogen, and oxygen.
There are two groups:
Simple carbohydrates (also called “sugars”)
Complex carbohydrates

3. The term “carbohydrate” refers to a group of molecules composed of carbon, hydrogen, and oxygen.
There are two groups:
Simple carbohydrates (also called “sugars”)
Complex carbohydrates
In fact, they are related:
The complex carbohydrates are formed by
linking together many simple carbohyrates
and
The simple carbohydrates can be formed by
breaking apart the complex carbohydrates
We get carbohydrates in our diets from eating
plants and, to smaller degree from milk and meat.

4. Simple Carbohydrates:
The simple carbohydrates are the monosaccharides
and the disaccharides

5. Simple Carbohydrates:
The simple carbohydrates are the monosaccharides
and the disaccharides
Although there are dozens of known monosaccharides and disaccharides, only a small number are important nutritionally because they are found in our food.
Monosaccharides: All have formula C6H12O6

6. Simple Carbohydrates: Monosaccharides
Glucose (also called “dextrose”) is the most abundant and most important monosaccharide.

7. Simple Carbohydrates: Monosaccharides
Glucose (also called “dextrose”) is the most abundant and most important monosaccharide. All green plants produce glucose from carbon dioxide, water, and sunlight (energy) Gives food a sweet taste Glucose is the primary “fuel molecule” our cells use to produce energy so It is the sugar carried around the body in the blood

8. Simple Carbohydrates: Monosaccharides
Fructose (also called “levulose” or “fruit sugar”) is also very sweet

9. Simple Carbohydrates: Monosaccharides
Fructose (also called “levulose” or “fruit sugar”) is also very sweet Occurs naturally in fruits, vegetables, honey, and corn syrup. Some cells can use fructose as a fuel molecule, but most cells convert it to glucose instead

10. Simple Carbohydrates: Monosaccharides
Galactose - rarely found alone in nature Usually combined with glucose

11. Simple Carbohydrates: Monosaccharides
Galactose - rarely found alone in nature Usually combined with glucose Found in milk Cells convert galactose to glucose for energy May be part of cell membranes

12. Simple Carbohydrates: Disaccharides
Disaccharides are two monosaccharides linked together

13. Simple Carbohydrates: Disaccharides
Disaccharides are two monosaccharides linked together Three disaccharides are dietarily important: Sucrose Lactose Maltose All have formula C12H22O11

14. Simple Carbohydrates: Disaccharides
Sucrose = glucose + fructose Found in sugarcane, sugarbeets “Table Sugar” – only sweetener that can be called “sugar” on food labels in United States

15. Simple Carbohydrates: Disaccharides
Lactose = glucose + galactose “Milk Sugar”

16. Simple Carbohydrates: Disaccharides
Maltose = glucose + glucose Found in partially digested starch and in germinating cereal grains

17. Complex Carbohydrates
Chains of two or more monosaccharides Oligosaccharides = shorter chains Polysaccharides = longer chains 17

18. Complex Carbohydrates: Oligosaccharides
Consist of 3-10 monosaccharides
Found in legumes, milk
Forms receptors on many cell membranes
Not digestible by humans = fiber
May be added to food: inulin
oligofructose
raffinose
maltotriose 18

19. Complex Carbohydrates: Polysaccharides
Starch:
How plants store energy
Found in grains, legumes, and tubers
Long chains of glucose units:
Amylose—straight chains
Amylopectin—branched chains 19

20. Complex Carbohydrates: Polysaccharides
Glycogen
How animals (including humans) store energy
Found in meat, liver
Long, branching chains
of glucose units:
Formed in liver and muscle when
blood glucose levels are high
Can be broken down to provide
glucose when blood glucose levels get low 20

21. Complex Carbohydrates: Polysaccharides
Cellulose
Indigestible chains of monosaccharides = “fiber”
- speeds up gastrointestinal movement
- increases fecal mass
- slows breakdown of starch
- slows absorption of glucose
Found in all plants,
“Functional” fiber: isolated and added to foods
Can be use as a supplement 21

22. Complex Carbohydrates: Polysaccharides
Other forms of fiber
= Indigestible chains of monosaccharides
Pectins
Gums
Lignans
Beta glucans
Chitins
Found in all plants,
“Functional” fiber: isolated and added to foods
Can be use as a supplement 22

23. Complex Carbohydrates23

24. Complex Carbohydrates:
Dietary fiber:
Possible role in weight control
Better control of blood glucose
Reduced risk of heart disease
Healthier gastrointestinal functioning
Negative effects of excess fiber
Increased water consumption
Can bind small amounts of minerals 24

25. Carbohydrate Digestion:
Complex carbohydrates (amylose, amylopectin) broken down to form disaccharides and monosaccharides:
Mouth: Salivary amylase begins digestion
Stomach: No carbohydrate digestion
Small intestine: Pancreatic amylase finishes digestion 25

26. Carbohydrate Digestion:
Disaccharides (sucrose, maltose, lactose) broken down to form monosaccharides:
Small intestine: Pancreatic enzymes
Enzymes from intestinal cells
(sucrase, maltase, lactase) 26

27. Carbohydrate Digestion:
These enzymes are highly specific For example: - Amylase digests amylose but not amylopectin - Lactase digests lactose but not maltose or sucrose - Maltase digests maltose but not lactose or sucrose - Sucrase digests sucrose but not maltose or lactose Remember: Some carbohydrates can not be digested; fiber & “resistant” starch 27

28. Carbohydrate Absorption:
Monosaccharides are absorbed from the small intestine 28

29. Carbohydrate Absorption:
Monosaccharides are absorbed from the small intestine and carried by the blood to the liver 29

30. Carbohydrate Absorption:
Monosaccharides are absorbed from the small intestine and carried by the blood to the liver
Liver: Converts other
monsaccharides
to glucose
Stores excess
glucose as
glycogen 30

31. Carbohydrate Absorption:
Monosaccharides are absorbed from the small intestine and carried by the blood to the liver
Liver: Converts other
monsaccharides
to glucose
Stores excess
glucose as
glycogen
Liver: Breaks down glycogen to release glucose back into the
blood when needed. 31

32. Carbohydrate Metabolism:
Glucose is our primary fuel source so
It is important to maintain normal blood glucose levels
and
It is important for glucose to get from the blood into cells 32

33. Carbohydrate Metabolism:
Glucose is our primary fuel source so
It is important to maintain normal blood glucose levels
and
It is important for glucose to get from the blood into cells
These processes are primarily regulated by two hormones
Insulin
Glucagon
Both are secreted by the pancreatic islets 33

34. Carbohydrate Metabolism:34

35. Carbohydrate Metabolism:
Insulin promotes:
(i) Energy storage
glucose glycogen (glycogenesis)
(ii) Protein synthesis
glucose amino acids protein
(iii) Fat synthesis
glucose fatty acids triglycerides(fat) 35

36. Carbohydrate Metabolism: Disorders
Normal Blood Glucose: mg/100 ml of blood 36

37. Carbohydrate Metabolism: Disorders
Normal Blood Glucose: mg/100 ml of blood
Persistent high blood glucose levels = Hyperglycemia
Insufficient insulin >125 mg/100 ml
Too much glucagon
Most common cause = diabetes mellitus 37

38. Carbohydrate Metabolism: Disorders
Normal Blood Glucose: mg/100 ml of blood
Persistent high blood glucose levels = Hyperglycemia
Insufficient insulin >125 mg/100 ml
Too much glucagon
Most common cause = diabetes mellitus
Persistent low blood glucose levels = Hypoglycemia
Too much insulin <50 mg/100 ml
Insufficient glucagon
Most common causes = insulin overdose in diabetes
starvation
strenuous exercise 38

39. Carbohydrate Metabolism: Disorders
Diabetes Mellitus:
Glucose unable to enter cells so
Blood glucose levels rise (hyperglycemia)
Complications: Hypertension
Heart damage
Kidney damage
Nerve damage
Blood vessel damage
Eye damage 39

40. Carbohydrate Metabolism: Disorders
Diabetes mellitus: Type 1 or “insulin dependent” diabetes: Lack of insulin production Type 2 or “insulin independent” diabetes: Cells are resistant to insulin 40

41. Carbohydrate Metabolism: Disorders
Diabetes mellitus: Type 1 or “insulin dependent” diabetes: Lack of insulin production Type 2 or “insulin independent” diabetes: Cells are resistant to insulin Usually present as “prediabetes” first Gestational diabetes: occurs during pregnancy 41

42. 42

43. Carbohydrate Metabolism: Disorders
Diabetes mellitus: Best prevention: Healthful diet Regular exercise Healthy weight Don’t smoke Monitor blood sugar if you have genetic predisposition 43

44. Carbohydrates: Recommended carbohydrate intake:
Recommended Daily Allowance = 130 grams per day
Acceptable Macronutrient
Distribution Range = 45–65% of calories 44

45. Carbohydrates: Recommended carbohydrate intake:
Recommended Daily Allowance = 130 grams per day
Acceptable Macronutrient
Distribution Range = 45–65% of calories
Choose carbohydrates wisely: fiber-rich fruits
vegetables
whole grains
high-fiber cereal
Because:
Not all carbohydrate sources have the same effect on blood glucose levels 45

46. Carbohydrates:
Each type of food has a glycemic index which measures its effects on blood sugar levels.

47. Carbohydrates:
Each type of food has a glycemic index which measures its effects on blood sugar levels.
Carbohydrates that break down quickly
during digestion and release glucose
rapidly for absorption into the bloodstream
have a high glycemic index

48. Carbohydrates:
Each type of food has a glycemic index which measures its effects on blood sugar levels.
Carbohydrates that break down quickly
during digestion and release glucose
rapidly for absorption into the bloodstream
have a high glycemic index
Carbohydrates that break down more
slowly, releasing glucose more gradually
for absorption into the bloodstream, have
a low glycemic index.

49. Carbohydrates: Low glycemic index: Most vegetables, fruits, legumes,
(55 or less) whole grains, nuts, milk, citrus
juices, foods low in carbohydrates
Moderate glycemic index: Whole wheat products, honey,
(56 to 69) brown or basmati rice, bran,
baked potato, sweet potato
High glycemic index: White bread, white rice, breakfast
(70 and above) cereals, waffles, chips, candy,
table sugar
(Pure glucose: glycemic index = 100) 49

50. Carbohydrates: Moderating sugar intake:
Choose food with lower glycemic index
Use less added sugar
Limit soft drinks, sugary cereals, and candy
Choose fresh fruits or those canned in water or juice 50

51. Carbohydrates: Natural and Artificial Sweeteners
Nutritive sweeteners
Natural sugars
Sugar alcohols
Non-nutritive sweeteners
Saccharin
Aspartame
Acesulfame K
Sucralose 51

52. Let’s move on to the lipids next