Chapter 4: CARBOHYDRATES: Sugar, Starches, and Fibre.

Chapter 4: CARBOHYDRATES: Sugar, Starches, and Fibre

Carbohydrates in the Modern Diet Carbohydrates are the basis of most modern

diets. Carbohydrates in “whole foods,” such as

fresh fruit, diary or whole grains, are in their natural state.

Refining carbohydrates separates the carbohydrates from their vitamins, minerals and fibre.

Copyright 2012, John Wiley & Sons Canada, Ltd.

Carbohydrates in the Canadian Diet Intake of carbohydrates in today’s diet is more refined

than in the past. Thirteen percent of kcalories consumed come from added sugars in desserts, beverages and purchased prepared snacks.

Canada’s Food Guide recommends that we eat more unrefined carbohydrates, such as whole grains, vegetables, legumes and fruits.

It is also recommended that Canadians decrease their intake of refined carbohydrates and added sugars from foods such as baked goods and soft drinks.


Carbohydrates in the Canadian Diet


Whole versus Refined Carbohydrates


Whole versus Refined Carbohydrates


Whole Grains versus Refined Grains Whole or unrefined grains contain:

Bran layers: good source of fibre and vitamins Germ: good source of vegetable oils and vitamin E Endosperm: contains starch and some protein


Whole Grains versus Refined Grains Refined grains, such as corn flakes or puffed

rice, are made largely from the endosperm and are mostly starch.

Refined grains sold in Canada may be enriched with thiamin, riboflavin, niacin and iron and fortified with folate. They do not contain the magnesium, Vitamin E, B6 or a number of other nutrients that are lost during processing.


Choosing Whole Grains To determine if a product is whole grain. look

for “whole grain” on the label and the ingredient list.

In 2008 Canada adopted the whole grain stamp developed by The Whole Grain Council (USA).

Canada’s Food Guide recommends that half of grain servings be whole grains.


Choosing Whole Grains


Added Sugars in Our Diet


Carbohydrates Carbohydrates in the diet are classified as:

Simple carbohydrates, also known as sugars Complete carbohydrates, which include starch

and fibre


Simple Carbohydrates The basic unit of a carbohydrate is a single

sugar molecule, known as a monosaccharide.

The three most common monosaccharides in the diet are glucose, galactose and fructose.

Glucose, also known as “blood sugar,” is the most important carbohydrate fuel for the body.


Simple Carbohydrates


Disaccharides

Disaccharides are simple carbohydrates made of two monosaccharides linked together.

Sucrose, or white table sugar, is formed by linking glucose with fructose.

The chemical reaction that breaks sugar molecules apart is called a hydrolysis reaction.

The chemical reaction that links two sugar molecules together is called a condensation reaction.


Structure of Disaccharides


Condensation and Hydrolysis Reactions


Complex Carbohydrates Complex carbohydrates are made up of

many monosaccharides linked together in chains.

Oligosaccharides are short chains of less than ten monosaccharides.

Polysaccharides are long chains of monosaccharides and include glycogen found in animals and starch and fibre found in plants.


Dietary Fibre Fibre includes certain complex carbohydrates that

cannot be digested by human enzymes. Fibre cannot be digested or absorbed by the human

body. Total fibre on a food label is the combined amount of

functional fibre and dietary fibre found in the food. Soluble fibre dissolves in water and can be found in

oats, apples and beans. Insoluble fibre does not dissolve in water and can be

found in wheat bran and fruit and vegetable peels.


Digestion and Absorption of Carbohydrates


Lactose Intolerance

The enzyme lactase is needed to digest lactose, the sugar found in milk.

If lactose is not digested in the small intestine, it passes through to the large intestine.

Undigested lactose in the small intestine can cause cramping, abdominal distention and diarrhea.


Indigestible Carbohydrates Slow Nutrient Absorption


Meeting Calcium Needs Canada’s Food Guide recommends 2 to 3

servings of milk and milk alternatives per day. To meet calcium requirements, individuals

who are lactose intolerant can: (if the intolerance is not too severe) divide milk

servings into smaller portions and spread them throughout the day

consume foods like tofu, fish and vegetables consume calcium-fortified foods, milk treated with

the enzyme lactase and lactase tablets.


Cellular Respiration

To generate energy, glucose is metabolized through cellular respiration.

Cellular respiration is also called aerobic metabolism.

Cellular respiration produces ATP, a form of energy. This metabolic pathway uses six molecules of

oxygen to convert one molecule of glucose into six molecules of carbon dioxide, six molecules of water and approximately thirty-eight molecules of ATP.


Cellular Respiration


Gluconeogenesis


Availability of Carbohydrates Determines Fatty Acid Metabolism


Regulating Blood Glucose In order to provide a steady supply of glucose to the cells,

the concentration of glucose in the blood is regulated by the liver and by hormones secreted from the pancreas.

Glycemic response is how quickly and how high blood glucose rises after carbohydrates are consumed.

The glycemic index is a ranking of how a food affects the glycemic response.

Insulin is a hormone secreted by the pancreas in response to a rise in blood glucose levels.

Glucagon is a hormone secreted by the pancreas in response to a decline in blood glucose levels.


Regulating Blood Glucose


Abnormal Blood Glucose: Diabetes

Diabetes is a major health problem in Canada. The Canadian Diabetes Association estimates that 3 million Canadians have diabetes and that this number will increase to 3.7 million by 2020.

Type 2 Diabetes is the most common form of diabetes (95% of cases).

Diabetes is the leading cause of blindness in adults, causes renal failure, and is the major reason for nontraumatic lower limb amputations.

Type 2 diabetes usually found in adults is now being seen in children. 95% of children with the condition are overweight.


Abnormal Blood Glucose Diabetes

The three main types of diabetes are: Gestational – occurs in women during

pregnancy. These women are at a greater risk for developing diabetes later in life.

Type I Diabetes – autoimmune disease in which the body’s own immune system destroys insulin-secreting cells. Insulin is no longer made.

Type 2 Diabetes – cells have decreased sensitivity to insulin and there is a decrease in insulin production.


Diabetes Symptoms and Complications Immediate symptoms: excessive thirst,

frequent urination, blurred vision and weight loss.

Long-term complications: damage to the heart, blood vessels, kidneys, eyes and nervous system. Infections are more common in patients with diabetes, and amputations may be necessary.


Blood-glucose levels in Diabetes


Diabetes Treatment The goal of diabetes treatment is to keep

blood glucose levels within normal ranges. Treatment includes a combination of diet,

exercise and, if necessary, medication, which can be oral or injected.

Evidence is accumulating that refined sugar may play a role in the development of type 2 diabetes.


Diabetes Treatment The Canadian Diabetes Association has developed

Just the Basics and Beyond the Basics to help individuals control their blood glucose levels.

Just the Basics is a simplified dietary plan instructing individuals to use a divided plate to ensure proper portions, choose whole grains, avoid simple sugars and have 3 meals per day at about the same time each day.

Beyond The Basics is a poster used for meal planning. Foods are divided into groups by carbohydrate content. The poster is filled in by a dietitian.


Diabetes Treatment


Carbohydrates and Dental Caries Dental caries occur when bacteria that live in

the mouth form colonies on teeth known as plaque.

If the plaque is not brushed or flossed away, the bacteria metabolize carbohydrates in the mouth and create acid.

The acid dissolves tooth enamel and the underlying structures of the teeth and gums.


Low-Carbohydrate Weight Loss Diets The rationale for low-carbohydrate diets is that

foods high in carbohydrates stimulate the release of insulin.

Insulin promotes energy storage, mostly from fat. The more insulin you release, the more fat you

store. Low-carbohydrate diets cause less insulin to be

released. With low-carbohydrate diets, the body produces

more ketones. Ketones help suppress the appetite.


Carbohydrates and Heart Disease

Diets high in sugar or refined carbohydrates have been shown to raise blood lipid levels and can lead to an increase in heart disease.

Diets high in whole grains have been found to reduce the risk of heart disease.


High Fibre Intake and Bowel Disorders

Diets high in fibre or indigestible carbohydrates can relieve or prevent certain bowel disorders:

Hemorrhoids Diverticulosis Diverticulitis Constipation


Colon Cancer and Fibre Intake Epidemiological studies have shown that the

incidence of colon cancer is lower in populations that consume diets high in fibre.


Selecting Healthy Carbohydrates


Carbohydrate Intake The RDA for carbohydrates is 130 g/day for adults

and children. This provides for the minimum amount of glucose used by the brain.

The AMDR for carbohydrates is 45 to 65% of energy.

The sources of carbohydrates should be unrefined, and no more than 25% of carbohydrates consumed should come from added refined sugars.

Canada’s Food Guide recommends that Canadians choose foods with little or no added sugar.


Tools for Assessing Carbohydrate Intake


Tools for Assessing Carbohydrate Intake


Reading Food Labels for Sugar and Fibre Content


How Much Added Sugar Do We Eat?


Choosing Carbohydrates Wisely


Alternative Sweeteners Alternative sweeteners are also called “nonnutritive

sweeteners.” Types of alternative sweeteners available in Canada

include: Cyclamte – a tabletop sweetener, limited sale. Saccharin – a tabletop sweetener, purchased in

pharmacies. Aspartame – a tabletop sweetener, used in foods that are

not cooked. Health Canada ADI 40 mg/kg body weight. (Equal, NutraSweet, NutriTaste)

Sucralose – a tabletop sweetener, used in foods, is heat stable. ADI 9 mg/kg body weight.(Splenda)


Alternative Sweeteners continued

Acesulfame K used if foods, heat stable. ADI 15mg/kg body weight.

Neotanme used in foods and heat stable. Sugar Alcohols – are chemical deriatives of

sugar. listed on the label under carbohydrate, provides less energy than sugar. (Mannitol, Sorbitol, Lacitol, Xylitol)


Copyright

Copyright © 2012 John Wiley & Sons Canada, Ltd.

All rights reserved. Reproduction or translation of this work beyond that permitted by Access Copyright (The Canadian Copyright Licensing Agency) is unlawful. Requests for further information should be addressed to the Permissions Department, John Wiley & Sons Canada, Ltd. The purchaser may make back-up copies for his or her own use only and not for distribution or resale. The author and the publisher assume no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information contained herein.

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Chapter 4: CARBOHYDRATES: Sugar, Starches, and Fibre.

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