Carbohydrates SESSI ON 2 DIETAR Y FIBER DR

Carbohydrates SESSI ON 2: DIETAR Y FIBER DR AZ ADE H NADJARZADEH AZADEHNA JA RZADEH@GM AIL. CO M

Session Overview for Instructor Key Messages n. Adequate amounts of dietary fiber help to maintain health and reduce risks of colon cancer and coronary artery disease n. Sources of dietary fiber in the food supply are: n. Grain products n. Vegetables n. Fruits n. Legumes, nuts, and soy 2

Fiber is the structural part of plants and is found in vegetables, fruits, grains and legumes. Most dietary fibers are polysaccharides, like starch, but they are not digestible. The human body lacks the enzymes needed to digest and absorb fiber. As a result fibers reach the lower intestine intact where intestinal bacteria can ferment some fiber.

Fiber

Fiber Nonstarch polysaccharide fibers ◦ Cellulose ◦ Hemicellulose ◦ Pectin ◦ Gums ◦ Mucilages Nonpolysaccharide fiber ◦ Lignins ◦ Cutins ◦ Tannins Resistant Starches

Types of Fiber There are many different types of fiber, in general fibers can be divided into two types based on their physical properties. ◦ Soluble fibers ◦ Insoluble fibers

Soluble Fibers Soluble fibers dissolve in water, form gels and are easily digested by bacteria in the lower intestine. ◦ Provides a feeling of fullness. ◦ Slow down the rate food leaves the stomach. ◦ May have a role with heart disease, diabetes and colon cancer Found in legumes and fruits

Insoluble Fiber Insoluble fibers absorb water and swell up resulting in a larger softer stool that is easier and quicker to pass. ◦ Provides a feeling of fullness ◦ Helps with intestinal function ◦ May help with colon cancer Found in grains and vegetables

Fiber and Health Both fiber types are important for health. Fibers are beneficial for many conditions; constipation, diarrhea, diverticular disease, heart disease, diabetes and colon cancer. Fiber is only one factor involved in these conditions.

Fiber and Health Foods high fiber have many factors that may be factors in lowering disease risk. ◦ ◦ ◦ High fiber Low in fat High vitamins (antioxidants) High in minerals High in phytochemicals

Intestinal Function Insoluble fibers absorb water resulting in a larger, softer stool that is faster and easier to eliminate, which can help with: ◦ Constipation ◦ Hemorrhoids ◦ Diverticular disease

Colon Cancer Both insoluble and soluble fibers may protect against colon cancer ◦ Insoluble fibers absorb water making a larger, softer stool which can: ◦ Dilute potential carcinogens ◦ Reduce transit time so the colon is exposed to any cancer causing substance for less time. ◦ Soluble fibers can bind bile acids, potential carcinogens, and increase their excretion.

Heart Disease As mentioned, soluble fibers can bind to bile acids and increase their excretion. With fewer bile acids in the intestine, less fat is absorbed. Also by increasing bile acid excretion, the liver must use its cholesterol to make new bile acids.

Diabetes Soluble fibers may have a favorable effect on blood glucose. Soluble fibers decrease the rate at which food is released from the stomach and delays glucose absorption into the blood. This may help prevent wide swings in blood glucose throughout the day.

Weight Management Foods rich in complex carbohydrates tend to be low in fat and added sugars which can help with weight management by providing fewer calories. In addition, as fibers absorb water they swell up creating a feeling of fullness and delaying hunger.

How Much Fiber The National Research Council set a Dietary Reference Intake (DRI) for dietary fiber. An adequate Intake (AI) for dietary fiber was set at 14 grams dietary fiber per 1, 000 calories. ◦ Thus for a reference 2, 000 calorie diet recommended intake would be 28 grams per day.

Too Much Fiber Dietary fiber can bind some minerals and decrease their absorption. However, if mineral intake is adequate a recommended dietary fiber intake will not compromise mineral balance. Fiber intake is like all nutrients - “more” is not always “better. ” Consuming a diet that provides a variety of nutrients is the key.

Food Sources of Fiber Foods are the best source of fiber, get both soluble and insoluble fiber. Food sources of fiber include fruits, vegetables, whole grain products, legumes, nuts and seeds. Cooking processing and removing peels can lower fiber content.

Tips for Increasing Fiber Increase fiber slowly. Increasing fiber too fast may cause bloating and gas. Since some fiber absorbs water it also is important to drink plenty of fluids when increasing dietary fiber.

Tips for Increasing Fiber Because fibers absorb liquids drink plenty of fluids when increasing fiber. As with all nutrients, “more” is not “better. ” Moderation is the key.

Summary of Dietary Fiber Classes Mosby items and derived items © 2006 by Mosby,

Other Sweeteners Nutritive sweeteners ◦ Sugar alcohols (sorbitol, mannitol, xylitol) Nonnutritive sweeteners ◦ Artificial sweeteners in food Mosby items and derived items © 2006 by Mosby, Inc. SLIDE 22

Sweetness of Sugars and Artificial Sweeteners Mosby items and derived items © 2006 by

Energy Function of Carbohydrates Basic fuel supply ◦ Energy for physical activities and all work of body cells Reserve fuel supply ◦ Provided by glycogen ◦ Maintains normal blood glucose level Mosby items and derived items © 2006 by Mosby, Inc. SLIDE 24

Special Tissue Functions of Carbohydrates Liver ◦ Glycogen reserves protect cells from depressed metabolic function Protein and fat ◦ Carbohydrates regulate proteins and fat (Cont'd…) Mosby items and derived items © 2006 by Mosby, Inc. SLIDE 25

Special Tissue Functions of Carbohydrates (…Cont’d) Heart ◦ Glycogen is vital emergency fuel for heart muscle Central nervous system ◦ Brain dependent on minute-to-minute supply of glucose Mosby items and derived items © 2006 by Mosby, Inc. SLIDE 26

Food Sources of Carbohydrates Starches ◦ Provide fundamental complex carbohydrates Sugars ◦ High-sugar diets

Carbohydrate Content of Foods (Cont'd…) Mosby items and derived items © 2006 by Mosby,

Digestion of Carbohydrates Mouth ◦ Mechanical or muscle functions break food mass into smaller particles Stomach ◦ Peristalsis continues mechanical digestive process (Cont'd…) Mosby items and derived items © 2006 by Mosby, Inc. SLIDE 30

Digestion of Carbohydrates (…Cont’d) Small intestine ◦ Peristalsis continues mechanical digestions ◦ Pancreatic secretions ◦ Intestinal secretions Mosby items and derived items © 2006 by Mosby, Inc. SLIDE 31

Summary of Carbohydrate Digestion Mosby items and derived items © 2006 by Mosby, Inc.

Body Needs for Carbohydrates Dietary Reference Intakes ◦ 45%-65% of adult’s total caloric intake should come from carbohydrate foods ◦ Limit sugar to no more than 25% of calories consumed Dietary Guidelines for Americans ◦ Does not outline specifics for caloric consumption or where kilocalories should come from Mosby items and derived items © 2006 by Mosby, Inc. SLIDE 33

Daily Recommendations of Dietary Fiber Needed* by Age/Gender Children Males Females Years Grams 1 -3 19 9 -13 31 9 -18 26 4 -8 25 14 -50 38 19 -50 25 51+ 30 51+ 21 *Recommendations, in grams, are based on Estimated Average Requirements (EARs). 34

Supplemental Information Background Information on the Dietary Reference Intakes n. The Institute of Medicine of the National Academy of Sciences publishes the Dietary Reference Intakes (DRI) for dietary components, including macronutrients, vitamins, minerals, and fiber. The DRIs consist of the RDAs, EARs, AIs, and ULs. n. Recommended values are provided for each life cycle group—from birth through childhood, sexual maturity, midlife, and old age. 35

Supplemental Information Dietary Reference Intakes, continued Nutrient Values Provided by the Dietary Reference Intakes n. Recommended Dietary Allowance (RDA) The average daily intake level sufficient to meet the nutrient requirements of 97 to 98 percent of healthy individuals. n Tolerable Upper Level (UL) The highest level of daily nutrient intake that is likely to pose no risks of adverse health effects to almost all individuals in the general population. 36

Supplemental Information Dietary Reference Intakes, continued n Estimated Average Requirement (EAR) The nutrient intake value sufficient to meet the requirements of half the healthy individuals in a group. The Nutrient Content of the U. S. Food Supply Series uses this DRI for nutrient comparisons. n. Adequate Intake (AI) The recommended daily intake based on approximations of nutrient intake by a group (or groups) of healthy people. It is used when the RDA cannot be determined. 37