MODULE 4 - PART I

refined

Refers to foods that have undergone processes that change or remove various components of the original food.

whole grain

The entire kernel of grain, including the bran layers, the germ, and the endosperm.

bran

The protective outer layers of whole grains. It is a concentrated source of dietary fibre

germ

The embryo or sprouting portion of a kernel of grain, which contains vegetable oil, protein, fibre, and vitamins.

endosperm

The largest portion of a kernel of grain, which is primarily starch and serves as a food supply for the sprouting seed.

fortified or enriched grains

Grains to which specific amounts of thiamin, riboflavin, niacin, and iron have been added. Since 1998, folic acid has also been added to enriched grains.

Free sugars

Monosaccharides and disaccharides added to food during processing or preparation and also the monosaccharides and disaccharides in honey, syrups and fruit juices.

added sugars

Sugars and syrups that have been added to foods during processing or preparation.

simple carbohydrates

Carbohydrates known as sugars that include monosaccharides and disaccharides.

complex carbohydrates

Carbohydrates composed of monosaccharide molecules linked together in straight or branching chains. They include glycogen, starches, and fibres.

monosaccharide

A single sugar unit, such as glucose.

disaccharide

A sugar formed by linking two monosaccharides.

glucose

A monosaccharide that is the primary form of carbohydrate used to provide energy in the body. It is the sugar referred to as blood sugar.

galactose

A monosaccharide that combines with glucose to form lactose or milk sugar.

fructose

A monosaccharide that is the primary form of carbohydrate found in fruit.

sucrose

A disaccharide that is formed by linking fructose and glucose. It is commonly known as table sugar or white sugar.

lactose

A disaccharide that is formed by linking galactose and glucose. It is commonly known as milk sugar.

maltose

A disaccharide made up of two molecules of glucose. It is formed in the intestines during starch digestion.

hydrolysis reaction

A type of chemical reaction in which a large molecule is broken into two smaller molecules by the addition of water.

condensation reaction

A type of chemical reaction in which two molecules are joined to form a larger molecule and water is released.

oligosaccharides

Short-chain carbohydrates containing 3–10 sugar units.

polysaccharides

Carbohydrates containing many monosaccharides units linked together.

glycogen

A carbohydrate made of many glucose molecules linked together in a highly branched structure. It is the storage form of carbohydrate in animals.

starch

A carbohydrate made of many glucose molecules linked in straight or branching chains. The bonds that hold the glucose molecules together can be broken by human digestive enzymes.

legumes

Plants in the pea or bean family, which produce an elongated pod containing large starchy seeds. Examples include green peas, lentils, kidney beans, and peanuts.

dietary fibre

A mixture of indigestible carbohydrates and lignin that is found intact in plants.

functional fibre

Isolated indigestible carbohydrates that have been shown to have beneficial physiological effects in humans.

total fibre

The sum of dietary fibre and functional fibre.

soluble fibre

Fibre that dissolves in water or absorbs water to form viscous solutions and can be broken down by the intestinal microflora. It includes pectins, gums, and some hemicelluloses.

lactase

An enzyme located in the brush border of the small intestine that breaks the disaccharide lactose into glucose and galactose.

insoluble fibre

Fibre that, for the most part, does not dissolve in water and cannot be broken down by bacteria in the large intestine. It includes cellulose, some hemicelluloses, and lignin.

lactose intolerance

The inability to digest lactose because of a reduction in the levels of the enzyme lactase. It causes symptoms including intestinal gas and bloating after dairy products are consumed

mouth

the enzyme salivary amylase starts breaking starch into shorter polysaccharides.

stomach

salivary amylase is inactivated by acid so no carbohydrate digestion occurs

small intestine

most starch digestion and breakdown of disaccharides occur. Here pancreatic amylases continue breaking down starch into monosaccharides, disaccharides, and oligosaccharides

Enzymes

attached to the brush border of the small intestinal villi complete the digestion of carbohydrates. Here, disaccharides and oligosaccharides are broken down into monosaccharides

large intestine

fibre and other indigestible carbohydrates are partially broken down by bacteria to form shortchain fatty acids and gas. Some fibre is excreted in the feces.

resistant starch

Starch that escapes digestion in the small intestine of healthy people

plasma

The liquid portion of the blood that remains when the blood cells are removed.

glycemic response

The rate, magnitude, and duration of the rise in blood glucose that occurs after a particular food or meal is consumed.

blood-glucose response curve

A curve that illustrates the change in blood glucose that occurs after consuming food.

insulin

A hormone made in the pancreas that allows the uptake of glucose by body cells and has other metabolic effects such as stimulating protein and fat synthesis and the synthesis of glycogen in liver and muscle.

glucagon

A hormone made in the pancreas that stimulates the breakdown of liver glycogen and the synthesis of glucose to increase blood sugar.

diabetes mellitus

A disease caused by either insufficient insulin production or decreased sensitivity of cells to insulin. It results in elevated blood-glucose levels.

hypoglycemia

A low bloodglucose level, usually below 2.2 to 2.8 mmol/L of blood plasma.

ketones or ketone bodies

Molecules formed in the liver when there is not sufficient carbohydrate to completely metabolize the 2-carbon units produced from fat breakdown.

gluconeogenesis

The synthesis of glucose from simple, noncarbohydrate molecules. Amino acids from protein are the primary source of carbons for glucose synthesis.

aerobic metabolism

Metabolism in the presence of oxygen. In aerobic metabolism, glucose, fatty acids, and amino acids are completely broken down to form carbon dioxide and water and produce ATP.

glycolysis (also called anaerobic metabolism)

Metabolic reactions in the cytosol of the cell that split glucose into two, 3-carbon pyruvate molecules, yielding two ATP molecules.

cellular respiration

The reactions that break down carbohydrates, fats, and proteins in the presence of oxygen to produce carbon dioxide, water, and energy in the form of ATP.

glycemic index

A ranking of the effect on blood glucose of a food of a certain carbohydrate content relative to an equal amount of carbohydrate from a reference food such as white bread or glucose

glycemic load

An index of the glycemic response that occurs after eating specific foods. It is calculated by multiplying a food’s glycemic index by the amount of available carbohydrate in a serving of the food

type 1 diabetes

A form of diabetes that is caused by the autoimmune destruction of insulin-producing cells in the pancreas, usually leading to absolute insulin deficiency; previously known as insulindependent diabetes mellitus or juvenile-onset diabetes.

type 2 diabetes

A form of diabetes that is characterized by insulin resistance and relative insulin deficiency; previously known as noninsulin-dependent diabetes mellitus or adult-onset diabetes.

insulin resistance

A situation when tissues become less responsive to insulin and do not take up glucose as readily. As a result glucose levels in the blood rise.

metabolic syndrome

A collection of health risks, including excess fat in the abdominal region, high blood pressure, elevated blood triglycerides, low high-density lipoprotein (HDL) cholesterol, and high blood glucose that increases the chance of developing heart disease, stroke, and diabetes. The condition is also known by other names including Syndrome X, insulin resistance syndrome, and dysmetabolic syndrome.

pre-diabetes or impaired glucose tolerance

A fasting blood-glucose level above the normal range but not high enough to be classified as diabetes.

gestational diabetes

A form of diabetes that occurs during pregnancy and resolves after the baby is born.

hemorrhoids

s Swollen veins in the anal or rectal area.

diverticula

Sacs or pouches that protrude from the wall of the large intestine in the disease

diverticulosis

When these become inflamed, the condition is called diverticulitis.

carcinogen

n A substance that causes cancer.

mutations

Changes in DNA caused by chemical or physical agents.

malignancy or metastasis

A mass of cells showing uncontrolled growth, a tendency to invade and damage surrounding tissues, and an ability to seed daughter growths to sites remote from the original growth.

sugar alcohols

Sweeteners that are structurally related to sugars but provide less energy than monosaccharides and disaccharides because they are not well absorbed.

beta-cell dysfunction

The malfunctioning of beta-cells of the pancreas, resulting in impaired secretion of insulin, an important factor in the development of Type 2 diabetes.

lipolysis

Breakdown of triglycerides to free fatty acids and glycerol

lipotoxicity

A toxic effect produced by the products of fatty acid metabolism by pathways other than fatty acid oxidation and triglyceride synthesis.

monosaccharide galactose is an important molecule in nervous tissue. combines with glucose to make lactose in women who are producing breast milk.

water

product of condensation reaction is

hydrolysis reaction

breaking sugar molecule bonds is

condensation

linking two sugars together is called

water

molecule that is needed for hydrolysis reaction

Insulin and glucagon, both produced in the pancreas, help to regulate blood glucose levels. The hormones have an opposing actions.

Insulin acts to prevent blood glucose levels from rising too much,

glucagon acts to prevent low glucose levels

A rise in blood glucose triggers the pancreas to secrete the hormone insulin, which allows glucose to be taken into the cells of the body

. Insulin is secreted by a specific type of pancreatic cell called the beta cell

0 In the liver, insulin promotes the storage of glucose as glycogen and, to a lesser extent, fat.

In muscle, insulin stimulates the uptake of glucose for energy production and the synthesis of muscle glycogen for energy storage

series of chemical changes in the cell, including the phosphorylation of a component of the receptor called tyrosine kinase (Figure 4.20b-step 2). This phosphorylation in turn permits the binding and phosphorylation of another protein called insulin-receptor substrates (IRS)

The end-result of these chemical changes or signals is to promote the movement or translocation of a protein called the GLUT4 transporter from a vesicle inside the cell to the cell membrane (Figure 4.20b-step 5). The GLUT4 transporter is important because it permits the entry of glucose into the cell

GLUT4 is considered especially important because its action largely depends on insulin and it is the transporter present in muscle and adipose tissue. It plays an important role in the maintenance of healthy blood-glucose levels.

When no carbohydrate has been consumed for a few hours, the glucose level in the blood—and consequently the glucose available to the cells—begins to decrease. This triggers another group of cells in the pancreas, the alpha cells, to secrete the hormone glucagon

glucagon,

signals liver cells to break down glycogen into glucose, which is released into the bloodstream.

Glucagon also stimulates the liver to synthesize new glucose molecules by gluconeogenesis

Gluconeogenesis can also be stimulated by the hormone epinephrine, also known as adrenaline. This hormone, which is released in response to dangerous or stressful situations, enables the body to respond to emergencies. It causes a rapid release of glucose into the blood to supply the energy needed for action.

Diabetes mellitus is a disease in which blood-glucose levels are consistently above the normal range

Hypoglycemia is a condition in which blood-glucose levels drop below the normal range.

Insulin stimulates the translocation of GLUT4 transporters from the cytoplasm of the cell to the cell membrane, allowing the entry of glucose into the cell. GLUT4 transporters are present in muscle and adipose tissue

glycemic index

describes the difference in glucose absorption, due to differences in soluble fibre content, glycemic index reflects the overall effect of the food, not just differences in fibre content

high-fibre and low-glycemic-index foods are not synonymous.

Glycemic index is measured by comparing the ratio of the area under a blood-glucose response curve for a portion of food containing 50 g of digestible carbohydrate (also referred to as available carbohydrate) compared to the response curve of 50 g of glucose (reference food)

Foods that have a glycemic index of 70 or more compared to glucose are considered high-glycemic-index foods; those with an index of less than 55 are considered low-glycemic-index foods

, the glycemic load was developed to take into account both the glycemic index of the food and the amount of carbohydrate in a typical portion

To calculate glycemic load, the grams of available carbohydrate in a serving of food are multiplied by that food’s glycemic index, expressed as a percent.

A glycemic load of 20 or more is considered high, whereas a value of less than 11 is considered low.