Principles of Food Science and Nutrition FIBER CARBOHYDRATE

Principles of Food Science and Nutrition FIBER &CARBOHYDRATE FUNCTIONS Dr. Nahlaa Khalifa

Fruit and veg Fibre Wholegrain cereal Beans Bread

Indigestible Polysaccharides ( Dietary Fibers ) • • Undigested plant food Beta glycosidic bond Fibers does not raise blood glucose level because it can not be broken into single sugar unit. Not fermented by the bacteria in the colon There are two types pf fibers based on whether the fiber dissolves in water into: Insoluble fibers (Cellulose, many hemicellulose, lignin) Soluble fibers (Gum, Pectin, Mucilage some hemicellulose) The soluble fiber tends to be gummy e. g (white apple , oatmeal ) whereas the insoluble fiber tends to be crunchy e. g ( apple skins , celery) ( Teaching pearl).

Impact of fiber on stool bulk , colonic motility l l l Cellulose and other insoluble fibers increase stool bulk directly by adsorbing water molecules into their structure so bran can be uses for the treatment of constipation and irritate bowel syndrome. Pectin , Gums and Some Hemicellulose in Fruits and Vegetables Increase Stool Bulk indirectly by Increasing Microbial Growth by Providing Nutrients to the Colonic Bacteria Over 50% of the Stool Bulk Is Bacteria , Thus the Influence of Soluble Fiber on Microbial Growth Is Impressive. For Example Cabbage Increases Stool Weight by 70% , but Very Little Cabbage Fiber Remains After Colonic Transit.

Impact of fibers on Short- Chain Fatty Acids Production l In Healthy Person , 70% - 80% of Dietary Fibers Is Metabolized in the Colon to Carbon Dioxide , Hydrogen, Methane and Short Chain Fatty Acids (SCFA). Acetate , Butyrate and Proprionate Account for About 85% of All SCFA Produced in the Human Colon. SCFA Are Readily Absorbed by the Intestinal and Colonic Mucosa and Have the Following Effect : 1

Impact of fibers on Short- Chain Fatty Acids Production 1. 2. 3. 4. 5. 6. 7. Enhance Water and Sodium Absorption Increase Colonocyte Proliferation Increase Metabolic Energy Production Enhance Colonic Blood Flow Stimulate the Autonomic Nervous System Increase Gastrointestinal Hormone Production Over 70% of the Fuel for Colonocytes Is the SCFA Butyrate

Impact of fibers on Short- Chain Fatty Acids Production 8. Butyrate Is Under Intensive Study for Its Ability to Inhibit Colon Carcinoma Cell Growth 9. Proprionate Is Absorbed and Cleared by the Liver Cell and May Be Important in Hepatic Lipid or Glucose Metabolism 10. Acetate is Rapidly Metabolized to Co 2 by Peripheral Tissues and Can Serve As Substrate for Lipid and Cholesterol Synthesis

RDA for Carbohydrate Food pyramid provides carbohydrates = 55 – 60% l FDA suggests the consumption of 20 g fibers daily. l ADA suggests the consumption of 20 – 35 g of fiber daily. l ADA recommends that intake for children should be equal to age in years + 5 g/day l

RDA for Carbohydrate • The amount of carbohydrate recommended ranges from low of 40 percent of total kilocalories or a minimum of 100 grams to prevent ketosis (rapid breakdown of body fat leading to a lowered PH or increase acidity levels of the blood ) • Guidelines found on food labels promote 60 percent of kilocalories or 300 grams carbohydrates for a 2000 kilocalorie diet. • The food groups in the Food Guide Pyramid (not including added sugars )is low of about 150 grams of carbohydrates to 300 grams.

What quantities of food are needed to meet the carbohydrate recommendation ? • To help translate carbohydrate grams into real food recommendations either the Dietary Exchange System or the Food Guide Pyramid may be used. • Carbohydrate content can be determined by assessing three factors : water content , level of sweetness and density. • There approximately 15 grams of carbohydrate for every half cup of grain or fruit or 1 cup of milk or plain yogurt.

What quantities of food are needed to meet the carbohydrate recommendation ? • Most vegetables provide 5 grams of carbohydrate for half cup cooked or 1 cup raw serving. • Dry plant such as potatoes and bread products contain on average 15 grams of carbohydrate for half cup. • A slice of bread provides a good size analogy for estimating carbohydrate e. g , a piece of pizza that is the size of a slice of bread contains one serving of starch (about 15 grams of carbohydrate

What Carbohydrates should we eat?

More whole Grains l The fiber in grains is found in the germ and the bran layer , where most of the nutritional value is found in whole grains l With any increase in fiber intake , an increase in water intake is needed to prevent fecal impaction.

Whole Grains

Whole Grains Refined carbohydrates usually retain all the calories of a whole grain but lose many of the nutrients l Before they are processed, all grains are whole grains consisting of an inner layer of germ, a middle layer called the endosperm, and an outer layer of bran l During processing, the germ and bran are often removed, leaving just the starchy endosperm. l

REFINED CHO VS WHOLE GRAIN • Whole grains are higher than refined carbohydrates in fiber, vitamins, minerals, and other beneficial compounds. • Whole grains take longer to digest. • Choose foods that have a whole grain as the first item on the ingredient list on the food label.

Guidelines to Groceries More whole Grains

Functions of Carbohydrate Supplies energy l Protein sparing: It spares the burning of protein for energy l Prevents ketosis l Sweetener l It aids in the more efficient and complete oxidation (burning) of fats for energy l

Functions of Carbohydrate l l l The primary function of dietary carbohydrate is to supply energy to body cells. They constitute the major source of energy in the synthesis of Adenosine Triphosphate (ATP), the fuel of a cell. Some cells, such as those in the brain, nervous system, and blood, use only carbohydrates for fuel During high-intensity exercise, muscles get most of their energy from carbohydrates

Functions of Carbohydrate l l Carbohydrate contribute to cellular structure and the synthesis of cellular products. They form the structure of DNA and RNA molecules. They may be converted to noncarbohydrate fractions, such as glycoproteins, to form structural components of the cell. They may be converted into a storage form, such as glycogen, that is readily available for conversion to glucose.

Functions of Carbohydrate How useful are polysaccharides? starch l Is stored in organisms as a future energy source e. g. potato has a high starch content to supply energy for the buds to grow later, it provides an economical and abundant source of energy after it is changed to glucose. Sugar and starch are both digested quickly in less than one hour. Glycogen l Is stored in the liver, which releases glucose for energy in times of low blood sugar Cellulose l Has long chains & branches which help form a tough protective layer around plant cells, the cell wall Pectins Are used alongside cellulose in the cell wall. They are polysaccharides which are bound together by calcuim pectate.

Functions of Carbohydrate How useful are polysaccharides? l l l As dietary fiber (insoluble and indigestible ), it aids in the normal functioning of the intestines. Soluble forms , in significant amounts , lowers serum cholesterol levels and lessens the after meal rise in blood glucose. Soluble fibers via oats ( 3 grams of fiber per 1 -ounce serving) has been shown to enhance the body use of insulin among persons with insulin resistance ( Pick et al. , 1996) Fibers slows down the time of digestion , which promote satiety (the feeling of fullness or being satisfied after eating) and allows for more stable blood sugars levels. As lactose , it has a certain laxative action and aids in the absorption of calcium

Problems caused by excess carbohydrate intake • • Obesity is the primary concern whenever one consume an excess of kilocalories for his need. Generally carbohydrates and fats are the chief kilocalorie leading to obesity. Persons who “graze” on carbohydrate foods throughout the day are more prone to dental caries. Good oral hygiene can help compensate for a person chooses to eat in this manner. Both sugars and starches are cariogenic (promoting dental cavities).

Problems caused by excess carbohydrate intake • • A high- serum triglyceride level (hypertriglyceridemia) will improve if one avoid an excessive intake of carbohydrate specially excess sugar intake because sugar is a concentrated form of carbohydrate Some individuals with diabetes need a moderate or low- intake of carbohydrate in order to maintain normal blood glucose level. Persons with diabetes can monitor their blood glucose levels to determine the ideal amount of carbohydrate for their personal needs. Although it is still in research stage , there is a growing evidence that persons with insulin resistance and the consequent hyperinsulinemia associated with a high-carbohydrate diet will benefit from a moderate intake of carbohydrate.

What quantities of food are needed to meet the carbohydrate recommendation ? Carbohydrate Counting It is the newest tool in diabetes self management. By focusing on the chief factor of elevated glucose - carbohydrate - meal choices become simpler and thus one can be more effective in managing blood glucose.

Why count carbohydrates? l l I. III. l Carbohydrate counting is a meal planning approach to maintain normal blood sugar. It is achieved by balancing: Carbohydrate intake Accurate amount of insulin Exercise Goal is to ensure sufficient normal growth and development while maintaining near-normal blood sugar level (Barrett, Goodwin & Kendrick, 2002).

Oligosaccharides 3 -10 monosaccharides l Found in beans and legumes l Not digested l Metabolized by bacteria in the large intestine l Beno® l Oligosaccharides: raffinose & stachyose l