1. Community Medicine Lecture -3-

2. Learning objectives
At the end of this lecture student would be able to :
1-Determine carbohydrates constituents .
2-Classify carbohydrates .
3-Identify functions of carbohydrates .
4-Illustrate types of dietary fibers .
5-Discuss the role of dietary fibers in managing certain health problems .
To a level accepted to the accreditation standard of the College .

3. Carbohydrates Carbohydrate is the main source of energy (4kcal).
 Carbohydrate is essential for the oxidation of fats and synthesis of certain non essential amino acids .
Three main sources of carbohydrates (starch , sugar and cellulose) .
 According to its constituents ,it is classified into:-
A-)Mono-saccharides or simple sugars including:-
1.)Glucose : This sugar occurs naturally in blood of living animals and in fruits and plants juices.
2.)Fructose: It is part of cane sugar. It is the sweetest sugar which present in plants juices, fruits and honey.
3.)Galactose:It is part of lactose molecule.

4.  It is composed of two monosaccharide molecules.
B-)Disaccharides
 It is composed of two monosaccharide molecules.
 It include :-
1.)Sucrose or the cane sugar which is composed of glucose and fructose molecules. It occurs naturally in sweet fruits roots such as carrot.

5.  It is composed of two glucose molecules.
2.)Lactose
 It is similar to sucrose but less sweetie.
 It occurs in milk in all animals including man.
 It is composed of glucose and galactose molecules
 It is useful in keeping calcium in children.
 Usually it is secreted with urine during
late pregnancy and lactation .
3.)Maltose
 It is composed of two glucose molecules.
 It is naturally formed from starch.

6.  Here ,several monosaccharides are linked together forming:-
C-)Polysaccharides
 Here ,several monosaccharides are linked together forming:-
1.)Starch
 Multiple glucose molecules linked together to form starch molecule
 It constitute a large proportion of human diet.
 Plants usually store a great part of its nutrients as a starch.
 Unripe fruits contain starch mainly.

7. 2.)Glycogen
 It is the only carbohydrate of animal origin.
 It is made inside the body from several glucose molecules.
 It is stored in the liver and muscles to be considered as a reserved fuel .
 This reserve is rapidly exhausted when a man is fasting .
Note :- Saccharine, which is one of the sweetie taste materials used in diabetes as a replacement material for cane sugar ,is not a carbohydrate material .It has a no energetic value towards human body .It is again a water soluble material that can be used through weight reduction food regimens of obese persons.

8. Functions of carbohydrates
I. Energy production
Carbohydrates are usually considered the main source for human energy supplement in diet.
 Although fatty diet has a higher caloric value ,but only a small amount of fatty materials are needed for essential fatty acids supplement .
 Carbohydrates are important in maintaining the energy reserve in human body.

9.  In adults :-
500 grams is stored in the liver and muscles in form of glycogen.
10 grams are present in blood as a circulating blood sugar .This amount of available glucose provide energy for only 12 hours a day in moderate activity.
Accordingly, each individual person should eat carbohydrates at regular intervals.

10. II. Special functions of carbohydrates
1.Glycogen reserves provide energy and protect the body cells from depressed metabolic function and injury.
2.Protein -sparing action
Carbohydrates help in regulating protein metabolism as the following mechanism :-
When sufficient carbohydrates are available in diet, proteins are spared for tissue building rather than energy production.

11. 3.Antiketogenic effect
Carbohydrates has also a role in fat metabolism . Its presence in diet determine how much fat will be broken down for energy ,thus will affect ketone bodies formation. So in cases of uncontrolled diabetes and in starvation, too much oxidation of fatty materials will results in ketone bodies accumulation leading to ketoacidosis.

12. 5.Central nervous system viability
4.Fuel for heart muscle
Although fatty acids are preferred as fuel for heart muscle ,glycogen is important fuel for emergency contractile energy supplementation .In aged heart , poor glycogen stores and low carbohydrates intake may cause cardiac insufficiency symptoms and angina.
5.Central nervous system viability
There is no glucose reserve in brain . Thus , a continuous glucose supply is essential to promote brain tissues viability .

13. 6.Dietary fibers functions :
a. Water absorption bulk of stool and tendency to constipation by encouraging bowel movement .
b. Making stool soft and pass easier through emulsification of fibers by bacterial action in large bowel .
c. Reducing intestinal transit time of food reducing possibility of putrefaction and formation of gasses and toxic substances .
d. Inhibits fecal mutagen synthesis by changing colonic PH and bacterial metabolism .
e. Reducing incidence of cancer of stomach and colon (cancer has direct association with low fiber diet) .

14. f. Reducing incidence of IHD (bind to bile salts and prevent its re-absorption and thus reducing cholesterol level in circulation) .
g. Fibers , particularly gum and pectin , when ingested with diet reduce postprandial glucose level in blood .
h. Too much fibers ingestion absorption of valuable micronutrients (some vitamins and minerals like iron & zinc and reduce their bioavailability) .
Note :
A daily intake of about 40 gm of dietary fibers is desirable .

15. Dietary fiber
It is mainly non starch polysaccharide which is physiologically important component of diet .
Types of dietary fibers
A-Cellulose form : which constitute the main framework of plants .
Human being cannot digest cellulose because of lack of enzymes which digest cellulose.
It form a bulk of food that regulate intestinal movement (i.e. stimulate peristalsis ).
Its sources include vegetables ,seeds and bran.

16. B-Non -cellulose polysaccharides:- It includes :
1- Hemicellulose pectin .
2- Storage polysaccharides e.g. inulin.
3- Plant gums and mucilages .
All are degraded to a greater or lesser extent by micro flora in human colon .
According to its solubility , dietary fibers classified into :
1- Insoluble fibers (cellulose, hemicellulose and lignin)
2- Soluble fibers (pectins, gums and mucillages).

17. Total fiber content of certain foods (gm/10gm)
Nil
Low(<1)
Medium(1-10)
High (>10)
Sugar
Refined & processed foods
Rice
Wheat
Fats/oil
Most vegetables
Jowar
Milk
Most fruits
Bajra
All types of meat
Coconut
Ragi
Seasam
Maize
Almonds
Legumes
Dates
Dhals
Fenugreek

18. Dietary fibers relation to certain health problems: Several studies revealed a constant relation between dietary fibers intake and the occurrence or prevention of certain health problems such as gastro-intestinal problems , cardiovascular problems , diabetes mellitus and cancer.
A-In diabetes mellitus :-
1.It reduces fasting blood sugar.
2.It reduces glucose urea.
3.It reduces insulin requirement.
4.It increases insulin sensitivity.
5.It inhibit the post prandial hyperglycemia through slowing carbohydrates absorption.

19. D-In colonic cancer:- It reduces the incidence of disease .
B-In obesity:- 1.It reduces energy density of diet. 2.It alter the normal responses. 3.It alter thermo genesis. 4.It reduces nutrients bioavailability.
C-In coronary heart disease:- 1.It inhibit the recirculation of bile acids. 2.It reduces the triglycerides and cholesterol levels.
D-In colonic cancer:- It reduces the incidence of disease .
E-In gastrointestinal problems:- (such as diverticulosis , hemorrhoids , constipation and irritable bowel syndrome) It increases the diameter of intestinal lumen.

20. Gastrointestinal function
*-Reduce the tendency to constipation by encouraging bowel movement and absorb water with increasing the bulk of the stool .
*-Making the stool soft and passage easier , so they are resistant to digestion in the digestive tract . In large intestine the bacterial action causes emulsification of the fiber .
*- Reducing the intestinal transit time of food .It drastically reduces the possibility of putrefaction and formation of gases and toxic substances .
*- Inhibits faecal mutagen synthesis by changing colonic pH and bacterial metabolism . Cancer of stomach and colon have been linked directly to a low fiber diet .

21. Thank You