Man shall not live by bread alone. Chapter 2 Carbohydrates Man shall not live by bread alone.

Key Concepts Carbohydrate foods provide practical energy (calorie) sources because of their availability, relatively low cost, and storage capability. Carbohydrate structures vary from simple to complex to provide both quick and extended energy for the body. Dietary fiber, an indigestible carbohydrate, serves separately as a regulatory agent within the gastrointestinal tract. Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Nature of Carbohydrates Relation to energy Basic fuel source Plants, through photosynthesis, transform solar energy into carbohydrate, which is the stored fuel form in plants. Energy production system Digests carbohydrate to produce glucose Absorbs glucose and transports it to cells Metabolizes glucose to ultimately release energy Dietary importance Widely available and easily grown Low cost Easily stored

Classes of Carbohydrates Saccharide = Carbohydrate class Simple carbohydrates have 1 or 2 sugar units Monosaccharides (1) Disaccharides (2) Complex carbohydrates have many sugar units Polysaccharides

Classes of Carbohydrates Monosaccharides Simple sugar Simple carbohydrate Glucose: basic single sugar in human metabolism Fructose: primarily found in fruits and honey Galactose: product of lactose (milk sugar) digestion Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Classes of Carbohydrates, cont’d Disaccharides Double sugar Simple carbohydrate Sucrose- common table sugar (glucose and fructose) Lactose- sugar found in milk (glucose and galactose) Maltose- product of intermediate digestive breakdown of starch within the body (glucose and glucose) Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Classes of Carbohydrates, cont’d Polysaccharides (complex carbohydrates) composed of many single-sugar units. Starch- the most significant polysaccharides Glycogen- formed within body tissues; crucial Dietary fiber- important dietary asset Glycogen

Starch Most significant polysaccharide in the diet Whole grains retain the bran layer, inner germ, and endosperm, including the nutrients naturally found in the plant Enriched grains are refined grains that have nutrients added back to them Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Dietary Fiber Dietary fiber cannot be broken down for energy in humans. Sources: Whole grains rice, wheat, corn, potatoes Legumes Vegetables Fruits with as much skin remaining as possible Health organizations emphasize role of dietary fiber Increases should be gradual Diets high in fiber can help prevent and treat disease

Dietary Fiber (cont’d) Benefits Lowers blood cholesterol levels Promotes normal bowel function and prevents constipation Increases satiety, which helps with the prevention of obesity Protects against disorders of the small and large intestines Slows glucose absorption, thereby reducing blood glucose spikes and insulin secretion. Health professionals can assist members of the public with evaluating their fiber intake by educating and encouraging the use of food labels.

Focus on Dietary Fiber, cont’d Divided into two groups based on solubility Insoluble-hold less water - relief of constipation (cellulose, most hemicelliloses, and lignin) Soluble- hold more water-binds bile acids-reducing blood cholesterol levels (gums, mucilages, Algals and most pectins) Many health organizations recommend increasing intake of dietary fiber 38 g/day for men 25 g/day for women Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Focus on Dietary Fiber Cellulose Remains undigested in the gastrointestinal tract and provides bulk to a diet Bulk helps move the food mass through the intestine (prevents constipaton) Examples: Stems, leaves of vegetables, corn hull, beans, coverings of seeds and grains Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Focus on Dietary Fiber, cont’d Noncellulose polysaccharides Absorb water and swell to a larger bulk, aids in satiety by slowing food passage through digestive tract and absorbing bile acids and cholesterol Examples: pectins from fruit; gums & mucilages – secretions from plants like okra; algal substances - seaweed Lignin Only noncarbohydrate type of dietary fiber Binds bile salts, cholesterol and metals Woody parts of plants (broccoli stems & seeds) Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Summary of Dietary Fiber Classes

Focus on Dietary Fiber, cont’d Sudden increases in fiber can result in gas, bloating, and constipation Excessive amounts of dietary fiber can trap small amounts of minerals and prevent their absorption into the gastrointestinal tract Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Other Sweeteners Nutritive sweeteners Non-nutritive sweeteners Sugar alcohols (sorbitol, mannitol, xylitol) Nutritive sweeteners that provide 2 to 3 kcal/g Non-nutritive sweeteners Artificial sweeteners in food Most common: acesulfame-K, aspartame, luohan guo, neotame, saccharin, stevia, sucralose

Energy Function of Carbohydrates Primary basic fuel supply Energy for physical activities and all work of body cells Reserve fuel supply Provided by stored glycogen Liver stores about 100 g of glycogen Primarily maintains blood glucose and ensures brain function Skeletal muscles can stores 300 to 400 g Available to maintain a normal blood glucose level

Special Tissue Functions of Carbohydrates Liver Stored glycogen protect cells from depressed metabolic function Protein and fat Carbohydrates regulate proteins and fat used for energy Heart Glycogen is vital emergency back up fuel for heart muscle Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Digestible Food Sources of Carbohydrates Central nervous system Brain dependent on minute-to-minute supply of glucose Starches Provide fundamental complex carbohydrates Sugars Readily absorbed Simple sugars are used to treat hypoglycemia High-sugar diets carry health risks Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Food Sources of Carbohydrates Starches Most important carbohydrate in the diet Whole-grain starches such as rice, wheat, corn, and potatoes Sugars Not necessarily bad Added sugars provide empty calories Moderation is key

Digestion of Carbohydrates Mouth Mechanical or muscle functions break food mass into smaller particles Chemical digestion begins with salivary amylase Stomach Peristalsis continues mechanical digestive process Gastric secretions mix with food particles to facilitate chemical digestion Secretions do not break down carbohydrates but stop action of salivary amylase Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Digestion of Carbohydrates, cont’d Small intestine Peristalsis continues mechanical digestion Pancreatic secretions - Enter duodenum through common bile duct Pancreatic amylase breaks starches down into disaccharides and monosaccharides Intestinal secretions - Sucrase, lactase, and maltase help break down their respective disaccharides to render the monosaccharides—glucose, galactose, and fructose—ready for absorption directly into the portal blood circulation.

Recommendations for Dietary Carbohydrates Dietary Reference Intakes 45% to 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, 2015-2020 Consume at least half of all grains as whole grains. Increase vegetable and whole fruit intake. Choose more nutrient-dense foods and less foods and beverages with added sugar. Reduce the intake of calories from added sugars to less than 10% of total calories. Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Summary Carbohydrates are the primary source of energy for most of the world’s population. Carbohydrates are distributed as the plant sources: grains, legumes, vegetables, and fruits. The two basic types of carbohydrates are simple and complex. Simple carbohydrates are composed of single- and double-sugar units (monosaccharides and disaccharides) Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Summary, cont’d Complex carbohydrates are composed of many sugar units. Dietary fiber is a complex carbohydrate that is not digestible and is found mainly in the structural parts of plants. Carbohydrate digestion begins in the mouth, continues in the stomach, moves to the small intestine, and finally arrives in the large intestine and exits through the anus. Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Lesson 3.1: Fats Dietary fat supplies essential body tissue needs, both as an energy fuel and structural material. Foods from animal and plant sources supply distinct forms of fat that affect health in different ways. Excess dietary fat, especially from animal food sources, is a negative risk factor in overall health. Copyright © 2013 Mosby, Inc., an imprint of Elsevier Inc. All rights reserved.

The Nature of Fats Dietary importance Concentrated fuel for energy Classes of fats Lipids Glycerides Triglycerides Fatty acids Lipoproteins Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved. 27

Fatty Acids ESSENTIAL fatty acids means that it is ESSENTIAL that we eat them Saturated fatty acids Filled or “saturated” with hydrogen Two essential fatty acids Linoleic Alpha-linolenic 28

Fatty Acids Unsaturated fatty acids Omega 3 and omega 6 Not completely filled with hydrogen Less heavy, less dense Monounsaturated: one unfilled spot Polyunsaturated: two or more unfilled spots Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved. 29

Fatty Acids (cont’d) Roles of essential fatty acids Related to tissue strength, cholesterol metabolism, muscle tone, blood clotting, and heart action Trans-fatty acid Hydrogen atoms around carbon double bond are on opposite sides (trans form) Negative health consequences related to cardiovascular disease Essential means these fats MUST come from the foods we eat. We cannot produce these as we can the other types of fatty acids.

Phospholipids Triglyceride derivative: third fatty acid replaced by phosphate group Partially hydrophobic, partially hydrophilic – remember cell wall? Allow transport of fats through bloodstream 31

Lipoproteins Lipoproteins: chemical complexes of fat+protein Major carriers of lipids in the plasma (since water and “oil” don’t mix) They vary in density according to the size of the fat load being carried (i.e., the lower the density, the higher the fat load). The combination package with water-soluble protein makes possible the transport of non–water-soluble fatty substances in the water-based blood circulation.

A QUESTION FOR YOU! Why are trans fats “worse” than saturated fats? Studies show they lower HDL cholesterol and raise LDL cholesterol, whereas saturated fats only raise LDL cholesterol, leaving HDL the same or better Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Lipoproteins (cont.)

Cholesterol Not a fat A fat-related compound (sterol) synthesized only in animal tissues (cell membranes) a normal constituent of bile a principal constituent of gallstones A fat-related compound (sterol) Only from animal foods Egg yolks Liver, kidney Meats Synthesized in the liver Diet should be low in cholesterol Linked with heart disease 35

Functions of Fat in Foods Fat in foods provide: Energy Essential nutrients Flavor and satisfaction Fat substitutes are not absorbed and therefore do not provide energy or essential nutrients but may provide flavor and satisfaction Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved. 36

Functions of Fat in the Body Adipose tissue Supports and protects organs Helps regulate temperature Cell membrane structure Forms part of cell membrane Helps transport nutrients across cell membranes Composes protective myelin sheath that surrounds neurons Second energy source Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved. 37

Food Sources of Fat Animal fats Plant fats The chief dietary supply of saturated fat and cholesterol comes from animal sources. Plant fats Plant foods supply mostly monounsaturated and polyunsaturated fats, including the essential fatty acids. Hydrogenated fats (trans fats) Commercial fat products raise health concerns Food industry now offers trans-free products Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved. 38

FDA Health Claims Claims that link one or more dietary components to the reduced risk of a specific disease need to be approved by the FDA Fat and cancer Saturated fat and cholesterol and heart disease Food label information Mandatory information Total fat Saturated fat Trans fat Cholesterol 39

Key Concepts Dietary fat supplies essential body tissue needs, both as an energy fuel and a structural material. Excess dietary fat, especially from animal food sources, is a negative risk factor in overall health. Food fat has 2 sources Visible fats butter, margarine, separate cream, salad oils and dressings, lard, shortening, poultry with skin Invisible fats Nuts, seeds, olives, skinless chicken, cream portion of milk Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved. 40

Dietary Fat and Health The American diet is high in fat. Excess calories are stored as fat. Animal food sources contribute to excess cholesterol and saturated fat in the diet. A decrease in saturated fat reduces serum total cholesterol. Monounsaturated fats reduce LDL cholesterol when substituted for saturated fat. Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved. 41

Digestion of Fats Mouth - mechanical Stomach - mechanical Small intestine – chemical & mechanical Bile (emulsifier) from the liver & gallbladder Enzymes from the pancreas (Pancreatic lipase) Enzymes from the small intestine The type of fat and cooking temperature affect the digestibility of fats. Fried food cooked at high temperatures are harder to digest and form carcinogins. 42

Absorption Since fats are not soluble in water they are not absorbed into the blood directly they are mixed with bile and form micelles to enter the epithelial cells. Bile is recycled by the hepatic portal system. Triglycerides are remade from digested fats and collet to form chylomicron to carry them with the cholesterol, phospholipids and protein to the lacteals of the lymph system and them to blood circulation. Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Dietary Fat and Health The American diet is high in fat. Amount of Fat Excess calories from any source are stored as body fat. Excess body fat is associated with higher rates of mortality and risk for chronic diseases. Type of Fat Omega-3 fats, when replacing saturated and trans fats, and monounsaturated fats are cardio-protective. Mediterranean diet Diets high in trans-fatty acids can raise LDL levels and lower HDL levels. FDA removed trans-fatty acids from GRAS food additives list requiring food manufacturers to discontinue use of partially hydrogenated oils (main source of trans-fatty acids) in any food product by 2018 Why are excess calories stored as fat and not carbohydrate or protein? (Explain that storing excess energy as fat is the way the body is supposed to work. It is a machine meant to store the most energy in the least amount of space.) Heart disease continues to be one of the leading causes of death in developed countries. Much attention is focused on reducing risk factors leading to this disease. GRAS list means generally recognized as safe.

Dietary Fat Requirements Healthy diet guidelines: Stress the health benefits of a diet low in fat overall, but more so with saturated fat, and cholesterol Recommend that the fat content should not exceed 20% to 35% of total kilocalories Less than 10% of kilocalories should be from saturated fat Dietary cholesterol should be limited to 300 mg/day Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved. 45

Dietary Fat and Health Essential fatty acid deficiency May result from following a fat-free diet Linked to health problems including: Hair loss Infertility Low blood platelet levels Impaired vision Compromised brain function Growth retardation in children

Health Promotion Reduce risk factors for chronic diseases, especially heart disease, the leading cause of death Obesity Diabetes Elevated triglycerides Elevated blood pressure Lifestyle risk factors = smoking, increased stress, physical inactivity Balance caloric intake with energy output [Ask students if they have noticed changes at restaurants with regard to fat content of foods.]

Dietary Guidelines for Americans Control saturated fat and cholesterol Keep trans-fatty acid consumption as low as possible Use only lean cuts of all meats; use more poultry and seafood (shellfish are low in fat but high in cholesterol) Limit eggs to two or three per week Can discard the yolk to decrease fat Use low-fat or fat-free milk and milk products Choose fat-free or low-fat milk and milk products. replace solid fats where possible. Avoid adding too much fat in food preparation – food should not slide across the plate! Slide 48 48

Summary Classes of fat include lipids, triglycerides, fatty acids, and lipoproteins Fatty acids can be saturated or unsaturated Essential fatty acids are necessary to aid in tissue strength, muscle tone, cholesterol metabolism, blood clotting, and heart action Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.

Summary, cont’d Cholesterol is a sterol only found in animal foods that is vital in human metabolism Digestion of fat includes digestive agents such as bile and pancreatic lipase Fatty acids and glycerides are incorporated into chylomicrons and absorbed via the lymphatic system into the bloodstream Copyright © 2009, by Mosby, Inc. an affiliate of Elsevier, Inc. All rights reserved.