Chapter 5: Carbohydrates

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Carbohydrates

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Fruit, Vegetables, Dairy Products, Breads etc.

They are the primary source of fuel for cells- central nervous system & red blood cells

4kcal/g

Glucose is the form of fuel in the blood and glycogen in the liver and muscles

Composed of Hydrogen, Carbon, and Oxygen

Fiber/sugar/strarch

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Monosaccharides

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simplest form of carbohydrates

simple sugars (glucose)

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Disaccharides

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Contain 2 sugars bonded together through a glycosidic bond

made of 2 monosaccharides

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Polysaccharides

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Most complex form of carbohydrates (glycogen, starch, fiber,)

They typically contain many glucose molecules linked together

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Glucose

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the most abundant monosaccharide - usually has to be broken down from di-polysaccharides

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Fructose

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a monosaccharide which is found in fruits, vegetables, honey (50% glucose & fructose) , high fructose sugar

The presence of these products in many foods makes it abundant in our diet

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Galactose

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The 3rd major monosaccharide

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Lactose

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When galactose and glucose combined by a beta bond

Found in milk and other dairy products

Many people are unable to digest this because they don't produce enough of the enzyme to break the beta bond. This causes intestinal gas, bloating, cramping, and discomfort as the unabsorbed lactose is metabolized into acids and gases by bacteria in the large intestine.

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hexose

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a carbohydrate containing 6 carbons

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condensation reaction

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the linking of 2 monosaccharides

a molecule of water is formed and a C-O-C bond is created.

Alpha bond-

Beta bond- harder to break down ( foods containing a saccharide molecules linked by a beta bond are harder to break).

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Maltose

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contains 2 glucose molecules join by an alpha bond

Most of the maltose we digest is produced when we break down longer-chain polysaccharides

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Sucrose

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Common Table sugar

composed of glucose and fructose linked by an alpha bond.

Large amounts of sucrose are found naturally in plants. There are different ways of processing i, which creates brown and white sugar

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Oligosaccharides

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complex carbohydrates that contain 3-10 simple sugar units.

Cannot be broken down by the bodies digestive enzymes (they are passed undigested into the large intestine, where bacteria metabolize them, producing gas and other by-products)

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Raffinose

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Oligosaccharide; indigestible and made of 3 monosaccharides (galactose-glucose-fructose)

found in onion, cabbage, broccoli, whole wheat, and legumes (kidney beans & soybeans)

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Starch

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Digestible polysaccharides

found in plants and is made of multiple glucose attached to each other in a way that the body can digest

Linked by alpha bonds

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Fiber

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complex carbohydrate in foods of plant origin that is made of multiple units of glucose attached together in a form that cannot be broken down by digestive processes in the stomach or small intestine

Linked by beta bonds

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type of plant starch

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Amylose

Amylopectin

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Amylose & Amylopectin

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a source of energy for plants and animal that eat plants

Found in potato, breads, pasta, rice, and other starchy products

Typically linked by alpha bonds.

Amylose - linear contains 1 type of alpha bond

Amylopectin- a highly branched-chain structure that links glucose molecules using 2 types of alpha bonds (1-4 straight; 1-6 bonds that link at branching points)

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Amylose

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Amylose - linear contains 1 type of alpha bond

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Amylopectin

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Amylopectin- a highly branched-chain structure that links glucose molecules using 2 types of alpha bonds (1-4 straight; 1-6 bonds that link at branching points)

causes blood glucose levels to increase more quickly than amylose as it has more branches (ends) available for enzyme action.

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1-4 bond

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alpha bonds that are broken by amylase enzymes produced in the mouth and pancreas

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1-6 bonds

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Alpha bond that are broken by an intestinal enzyme called alpha-dextrinase.

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Glycogen

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The storage form of carbohydrates in humans and other animals, also contains many glucose units linked together with alpha bonds

It is more branched than amylopectin this allows it to be broken down quickly by enzymes in the body cells where it is stored

In liver and muscle cells

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Total Fiber

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Dietary and functional fiber in food

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Dietary fiber

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fiber naturally in food

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Functional Fiber

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Fiber added to food to provide health benefits

Nutrition labels do not include functional fiber

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What are fibers mostly composed of?

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Cellulose, hemicelluloses, pectins, gums and mucilages

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Lignins

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the only noncarbohdyrate components of dietary fibers.

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Insoluble fibers

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Fibers that are not easily dissolved in water or metabolized by bacteria in the large intestine; include cellulose, some hemicelluloses, and lignin

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Soluble Fibers

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Fibers that dissolve in water and can be metabolized (fermented) by bacteria in the large intestine; include pectin, gums, and mucilages,; also called viscous fibers

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Foods that contain starch

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plant based foods- legumes, tubers, and the grains (wheat, rye, corn, oats, barley, and rice)

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Food that contain fiber

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legumes, tubers

fiber in whole grains is found in the outer layers which are removed in processing, highly processed grains are low in fiber.

Soluble fiber is found in the skins and flesh of many fruits and berries

Can get it in a supplement

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Nutritive sweeteners

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these can be metabolized to yield energy

ex: glucose, fructose, and galactose etc.

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Alternative sweeteners

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provide no energy when metabolized

These are much sweeter on average than the nutritive sweeteners

ex: Stevia, Neotame, Aspartame, Splenda

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Sugar Alcohols

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They are not readily metabolized by bacteria in the mouth. Sugar alcohols contribute energy (1.5-3 kcal/g) butt they are absorbed and metabolize to glucose more slowly than sugars

In large amounts they can cause diarrhea

ex: sorbitol mannitol a xylitol are nutritive sweeteners

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Acceptable Daily Intake (ADI) for alternative sweeteners

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Estimate of the amount of a sweetener that an individual can safely consume daily over a lifetime. ADIs are given as mg per kg of body weight per day.

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Saccharin

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the oldest alternative sweetener

it is 300x times sweeter than glucose

ADI at 5mg/kg body weight

It is not useful in cooking because heating causes it to develop a bitter taste

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Aspartame

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Alternative Sweetener

It breaks down when heated and loses its sweetness when foods are cooked or heated.

Nutrasweet and Equal

it is 180x or 200x times sweeter than sucrose

ADI= 50 mg/kg of weight

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Neotame

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Is approved by the FDA. IT his used as a general purpose sweetener in a wide variety of food products.

It is stable in heat and can be used in cooking

it is approximately 7000x sweeter than sucrose.

It contains phenylalanine its bonding to other amino acids differs from that of asparatame and prevents it from being broken down.

The ADi for neotame is 18mg/kkg

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Acesulfame-K

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It contributes no energy energy to the diet because it is not digested by the body

Can be used in baking because it does not lose its sweetness when heated

The ADI for acesulfame-K is 15 mg/kg

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Sucralose

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Sold as splenda it is 600x sweeter than sucrose. It is made by substituting 3 chlorines (Cl) for 3 hydroxyl groups (-OH) on sucrose. This substitution keeps it from being digested and absorbed. It is stable and can be used in cooking and baking.

The ADI is 5 mg/kg

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Tagatose

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Naturlose

it is an isomer of fructose. It is almost as sweet as sucrose but provides no energy.

It is poorly absorbed by the body, tagatose yields only 1.5 kcal/g. It has a prebiotic effect because it is fermented by bacteria in the large intestine.

It is metabolized like fructose, so individuals with disorders of fructose metabolism should avoid using it.

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Stevia

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It is an alternative sweetener derived from a plant from the Amazon rain forest. It is 100x to 300x sweeter.

4mg/kg

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Recommended Intake of Carbohydrates

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an adult 130 g/day of digestible carbohydrates to supply adequate glucose for the brain and central nervous system to prevent the partial replacement of glucose by kettle bodies as an energy source.

Carbohydrate intake should be around 45-65% of total energy intake.

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Carbohydrate Intake

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Carbohydraetes supply 50% of the energy intake of adults in North America.

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Digestible Carbohydrates

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Most of the digestible carbohydrates in our diets are broken down to glucose. As glucose, they provide a primary source of energy, sure protein from use as an energy source, and prevent ketosis

Fuels muscle cells and other body cells, these cells rely on fatty acids to meet energy needs, especially during rest and light activity

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Gluconeogenesis

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The production of new glucose

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Uses of digestible Carbohydrates

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1. providing energy

2. Sparing protein from use as an energy source

3. Preventing ketosis

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Preventing ketosis

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a minimum intake of carbohydrates is necessary to prevent ketosis. When these levels fall insulin decreases resulting in the release of a large amount of fatty acids from adipose tissue to provide energy for body cells. These fatty acids travel in the bloodstream. The subsequent incomplete breakdown of these fatty acids in the liver results in the formation of ketone bodies.

cells will use ketones for energy when carbohydrate intake is inadequate.

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Indigestible Carbohydrates

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Fiber- indegestible

It maintains the integrity of the GI tract and overall health. It helps prevent constipation and diverticular disease, enhances the management of body weight, blood glucose levels, and blood cholesterol levels

1. Promotes bowel health - adds bulk to feces (makes large and soft because fibers absorb water)

2. Reducing Obesity Risk - fiber aids weight control as it fills us up without yielding much energy. It also absorbs much water and expands in the GI tract which may result in a sense of fullness.

3. Enhancing Blood Glucose Control- fibers slow glucose absorption from the small intestine and decrease insulin released from the pancreas.

4. Reducing Cholesterol Absorption- inhibits the absorption of cholesterol and the reabsorption of bile acids from the small intestine therefore reducing the risk of cardiovascular disease and gallstones.

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Diverticula

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The high pressure from exertion of feces (caused by too little fiber) which can cause parts of the large intestine wall to protrude through surrounding bands of muscles

Fibrous material, feces, and bacteria can become trapped in diverticula and lead to inflammation

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Diverticulosis

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condition of having many diverticula in large intestine

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Diverticulitis

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Inflammation of the diverticula caused by acids produced by bacterial metabolism inside the diverticula

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Digestion of Carbohydrates

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1. mouth- saliva contains the enzyme amylase which breaks down the starch into smaller polysaccharides and disaccharides

2. Stomach- salivary enzyme is inactivated by acidity of stomach. Digestion of carbohydrate stops until it reaches the small intestine

3. Pancreas- pancreatic amylase and dextrinase are secreted into the small intestine to break polysaccharides from starch into disaccharides

4. Small intestine- Enzyme in the wall of the small intestine break down the disaccharides into monosaccharides. Sucrase - sucrose, Lactase - lactose, maltase- maltose

5. Liver- the absorbed monosaccharides are transported to the liver by the portal vein

6. Large intestine- some soluble fiber is metabolized into acids and gases by bacteria in the large intestine

7. Rectum and Anus - insoluble fiber escapes digestion and is excreted in feces

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Absorption

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monosaccharides are absorbed by an active absorption process. Following digestion, glucose and galactose are pumped into the absorptive cells along with sodium. The ATP energy used in the process pumps sodium back out of the absorptive cell.

Fructose is taken up by the absorptive cells via facilitated diffusion. No energy is needed but a carrier is used. This is slower than glucose or galactose. Once it enters the intestinal cells glucose and galactose remain in that form where fructose is converted to glucose.

They are transported via the portal vein to the liver. There fructose and galactose are converted to fructose. Glucose is transported through the bloodstream for use by the cells of the body.

If blood glucose levels are adequate then glucose is stored as glycogen. The liver can only store so much otherwise its converted to adipose fat.

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Very-High-Fiber-Diets

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adequate fiber intake provides many health benefits. Very high intakes of fiber can lead to health risks.

hemorrhoids, rectal bleeding - caused by extra pressure

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High-Sugar Diets

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Most of the sugar we eat comes from food and beverages to wich sugar has been added during processing or manufacturing. Although sugars supply calories they usually provide little else and often replace the intake of more nutritious foods. Children and adolescents are at the greatest risk of over consuming sugar.

can lead to weight gain and obesity. Increased risk of cardiovascular disease.

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Lactose Intolerance

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the enzyme lactase is produced in the small intestine if there is insufficient lactase this can lead to primary lactose intolerance.

It causes bloating gas and diarrhea after consumption of lactose

Secondary lactose intolerance which occurs when condition of the small intestine such as Crohn's diseases and severe diarrhea damage the cells that produce lactase.

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Glucose Intolerance

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Abnormal blood glucose levels

Hyperglycemia (high blood glucose)

Hypoglycemia (low blood glucose)

Liver- controls the amount of glucose in the bloodstream

Pancreas- releases insulin which promotes the storage of excess glucose as glycogen

Glucagon- promotes breakdown of glycogen in liver

Epinephrine (adrenaline) and norepinephrine - triggers breakdown of glucogen

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Glucagon

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hormone in the body

it is secreted in the pancreas to promote the breakdown of glycogen in the liver and promotes gluconeogenesis resulting in the release of glucose to the blood stream and the normalization of blood glucose levels.

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Metabolic Syndome

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a group of factors that increase the risk of type 2 diabetes and cardiovascular disease including insulin resistance or glucose intolerance, abdominal obesity, high blood triglycerides and LDL-cholesterol with low HDL-cholesterol, elevated blood pressure, increased inflammatory blood proteins, and higher concentrations of oxidized

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Hypoglycemia

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low blood sugar occurs with and without diabetes

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Reactive Hypoglycemia

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Lo blood glucose that may follow a meal high simple sugar, with corresponding symptoms of irritability, headache, nervousness, sweating, and confusion; also called postprandial hypoglycemia

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Fasting hypoglycemia

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Low blood glucose that occurs after 8 or more hours of fasting

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Glycemic Index (GI)

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blood glucose response of a given food, compared with a standard (typically glucose or white bread)

influenced by a foods starch structure, fiber content, food processing, physical structure, and temperature as well as the amount of protein and fat in a meal.

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Glycemic Load

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Amount of carbohydrate in a good multiplied by the glycemic index of the a food. The result is then divided by 100.