http://www.whfoods.com/genpage.php?tname=george&dbid=115

Carbohydrates are a varied combination of both very small and very large molecules that comprise about 40 to 45 percent of the energy supply for your body. In addition, certain types of carbohydrates, such as fiber and resistant starches don't get taken into your body for energy, but play important health-promoting roles in your gastrointestinal tract, supporting digestion and absorption, and helping you eliminate toxins and waste products.

Carbohydrates are are composed of carbon, hydrogen, and oxygen, which are arranged into small units called sugars, or monosaccharides. Small carbohydrates, like glucose or sucrose (table sugar) are composed of one or two sugar units, respectively, and are the molecules that give food a sweet taste. These molecules are sometimes called "simple sugars" because they are small (only one or two units), and are quickly digested, providing immediate energy to the body.

Larger carbohydrate molecules, which include fibers and starches, are composed of at least 10 monosaccharides linked together. These large carbohydrates, called polysaccharides (poly=many) may contain up to several hundred monosaccharides linked together in different ways. Another term commonly used to describe carbohydrates is oligosaccharides, a type of carbohydrate molecule that is in-between polysaccharides and monosaccharides in size, and features two to ten monosaccharides bonded together.

Let's look at each of these types of carbohydrates and how the food you eat influences the quality of these important nutrients you receive.

The Simple Sugars: Monosaccharides and Disaccharides

Monosaccharides

Monosaccharides are true simple sugars since, as one sugar unit only, they exist in the form in which they can be directly absorbed into your body upon ingestion. Unlike the other carbohydrates, they don't require being broken down during digestion, so when you eat a food containing monosaccharides, these sugars quickly get into your bloodstream, increasing your blood sugar and providing immediate energy. Examples of monosaccharides include glucose, fructose and galactose.

Monosaccharides are present in most foods in at least some amount, but are particularly high in foods such as ripe fruit, andhoney. Monosaccharides are an important energy source, but when too much of these simple sugars are

consumed at once--especially when they are not balanced by complex carbohydrates like oligosaccharides or polysaccharides that take longer to digest and thus help maintain longer-term energy production--monosaccharides can cause a large increase in blood sugar, followed by an abrupt drop. The result is a jolt of energy quickly followed by a feeling of being tired, shaky, or run-down soon afterward. This type of fluctuation in blood sugar, if it occurs frequently, can lead to blood sugar dysregulation conditions such as hypoglycemia and diabetes mellitus. Proceesed foods often add high amounts of monosaccharides such as fructose and glucose to promote a sweet taste, which sells more product, but does not sustain health.

Disaccharides

Disaccharides contain two monosaccharides (di=two) bonded together, and include sugars such as lactose (milk sugar), sucrose (table sugar), maltose and isomaltose (sugars formed from the breakdown of starch). Disaccharides are similar to monosaccharides; that is, they provide sweet taste to food and quick energy, which is why they are considered "simple sugars" as well. As such, disaccharides also are highly represented in processed foods, and their frequent consumption can lead to blood-sugar disregulation, the same as monosaccharides.

Since these carbohydrates contain two sugars, disaccharides require some digestion to break them into two one-sugar units for absorption, and since each disaccharide is unique, each has its own digestive enzyme. For example, the enzyme sucrase can cut sucrose into its two individual sugar units; lactase cuts lactose into its two sugars. For most disaccharides, these enzymes area readily secreted into the intestines after consuming a meal, and digestion of the disacchrides proceeds rapidly. The exception appears to be with lactose (milk sugar).

Many people lack the enzyme lactase and are therefore unable to breakdown lactose, a condition called lactose intolerance, which makes the consumption of dairy products problematic for many people. Lactose intolerance, which occurs more frequently as we age, is quite common in adults. In lactose intolerance, the undigested lactose is not absorbed and can promote growth of unfriendly bacteria in the upper intestinal tract, a condition called small bowel overgrowth. These bacteria ferment the lactose, producing gas in the small intestine that causes great discomfort, along with acid, which can cause heartburn and nausea. Even more problematic, the acid produced by this bacterial fermentation can degrade the lining of the small intestine, injuring the intestinal tract cells. This damage compromises the ability of the intestinal cells to produce enzymes for digestion, so even less disaccharide digesting enzymes are produced, and a

cycle of maldigestion is perpetuated. Diets that limit disaccharides may be of benefit for persons with these concerns, and a person with lactose intolerance should not consume lactose-containing foods without having a source of lactase either in the food or taken with the food. Some studies suggest that Lactobacillus supplements are beneficial in this respect as well.

The Polysaccharides: Starch, Fiber and Resistant Starch Starch

Plants store their energy by stringing together many glucose units into a long complex of several hundred to several thousand sugar (glucose) molecules. Plant foods that contain stored energy, for example seeds that must provide energy for the young plant when it starts growing, are high in starch. When the young plant starts growing, the starch is broken down into glucose for energy.

Starch

When you eat foods that contain starch, like corn or potatoes, your body uses this starch in much the same way. Since your body must breakdown this very large molecule to individual sugar units before they can be digested, the digestion of starch takes longer than that of disaccharides; therefore, starch provides an extended, or sustained source of energy. Because they do not lead to immediate bloodsugar spikes followed by a low, but instead a more moderate, longer-term elevation of blood sugar, starches are thought to be better for health and energy.

Starches are called complex carbohydrates because they are so large. Two main types of starches exist in food: amylose and amylopectin. These starches differ in how the individual sugars they contain are linked together. This difference results in differences in how easy it is for your body to cut the starches into their individual sugar units. Amylopectin is more quickly digested than is amylose; therefore, foods that contain higer amylose than amylopectin are often suggested as substitutions for people with bloodsugar control problems, like diabetes.

Starch digestion is also influenced by how the starch is packed in the food. When food is whole, or in its natural state, marcromolecules are folded together, and starch can be encased in protein or fiber or other large molecules that must be digested before the starch itself becomes available for digestion. The result of this packaging, again, is to slow down the absorption of the individual sugar units from the starch, and to provide extended, sustained energy for a longer-term, moderate rise in blood sugar after a meal. In contrast, processed foods have removed this complex interaction. In processing, the macromolecules are initially pulled apart from each other then added back separately. The result is starch that is more accessible for quick digestion and absorption causing quicker, higher

rises in blood sugar, which makes it look more like a disaccharide than a starch. Therefore, people with blood sugar control concerns, such as hypoglycemia, insulin resistance or diabetes can benefit from eating whole foods and avoiding high-starch, processed foods.

Fiber

Dietary fibers are also polysaccharides and are, therefore, considered complex carbohydrates; however, the sugar units in fiber are linked (bonded) together in such a way that your body can't break the bonds and digest them. Instead, fibers transit through your small intestines and make it all the way to your large intestine intact. This ability to move through your system to your large intestine helps speed the transit times of wastes excreted from your body; for this reason, fiber helps to support your health by reducing constipation and promoting the excretion of toxins and wastes.

Fibers that promote overall healthy digestion and waste excretion are found in vegetables, grains, and legumes and are well represented in whole foods. Often, when processed, foods have these fibers removed. For example, bran contains high levels of fibers and is removed when grains are processed. Fruit skins are also high in fiber, but are often removed when the fruit is processed for a fruit-containing product.

Much has been written about the health-promoting benefits of fiber, and ample numbers of studies support an association between high-fiber diets and a decrease in risk of many types of cancers, including colon cancer and breast cancer. Some of this benefit comes from the ability of fiber to bind and remove toxins, and to promote healthy digestion. Recent research suggests, however, that fiber provides its health-protecting benefits in other ways as well, and one of the most important appears to be its ability to promote healthy intestinal tract bacteria.

Your large intestine contains a multitude of beneficial bacteria that are required for your body's health. They are called the "friendly flora," or the beneficial symbiotic microbes, and they support the health of your whole body by promoting healthy immune function and providing important molecules to your intestinal tract cells to promote their growth, thus sustaining overall intestinal tract integrity. These microbes use some of the fibers you eat as fuel for their own growth, and through their own metabolism produce molecules called short-chain fatty acids (SCFA). SCFA production by these friendly flora has been associated with a decrease in cancerous colonic cells, reduction of serum cholesterol, and maintenance of healthy blood sugar levels and healthy intestinal tract cell walls.

Not all fiber is fermented by the friendly flora in your intestinal tract. Some, as discussed above, goes through your entire system unchanged, binding toxins and waste products as it goes, and promoting healthy elimination. Some fibers can be fermented by microbes of all types, while other fibers are preferentially fermented by the "friendly flora," the bacteria that are most beneficial to your body, including Bifidobacteria and Lactobacillus. When these friendly bacteria are given their favorite types of fibers, called "prebiotic fibers," they will flourish, significantly improving the health of your digestive tract. Excellent sources of these prebiotic fibers include foods such as Jerusalem artichoke, chicory, rice fiber, and soy fiber.

The classical way of talking about fiber to divide it into two types, soluble or insoluble fiber, a classification determined by how much water a type of fiber holds. New research, however, suggests that fiber has a multitude of activities besides holding water, and that this classical distinction is not adequate. Providing a full range of all types of fibers, including prebiotic fibers, will support your immune system, and enhance healthy digestion, absorption, and the removal of wastes and toxins. In fact, the health of your gastrointestinal tract is dependent upon your consumption of the variety of fibers well-represented in the World's Healthiest Foods.

Resistant Starch

A final category of polysaccharides, or complex carbohydrates, is that of resistant starch. Resistant starch gets its name because, although it is starch, it is resistant to digestion in the small intestine. The result of this resistance is that this type of starch acts more like fiber than starch, and travels through the intestinal tract until it reaches the large intestine where, like fiber, may be fermented by the bacteria in the colon. Research has shown that resistant starch promotes the generation of SCFAs by the bacteria in the large intestine, and therefore has many of the same health-promoting abilities as fiber. Resistant starch is found in whole grains such as brown rice, barley, whole wheat, and buckwheat.

http://kidshealth.org/parent/general/body_basics/digestive.html

The first step in the digestive process happens before we even taste food. Just by smelling that

homemade apple pie or thinking about how delicious that ripe tomato is going to be, you start

salivating — and the digestive process begins in preparation for that first bite.

Food is our fuel, and its nutrients give our bodies' cells the energy and substances they need to

operate. But before food can do that, it must be digested into small pieces the body can absorb and

use.

About the Digestive SystemAlmost all animals have a tube-type digestive system in which food enters the mouth, passes through

a long tube, and exits asfeces (poop) through the anus. The smooth muscle in the walls of the tube-

shaped digestive organs rhythmically and efficiently moves the food through the system, where it is

broken down into tiny absorbable atoms and molecules.

During the process of absorption, nutrients that come from the food (including carbohydrates,

proteins, fats, vitamins, and minerals) pass through channels in the intestinal wall and into the

bloodstream. The blood works to distribute these nutrients to the rest of the body. The waste parts of

food that the body can't use are passed out of the body as feces.

Every morsel of food we eat has to be broken down into nutrients that can be absorbed by the body,

which is why it takes hours to fully digest food. In humans, protein must be broken down into amino

acids, starches into simple sugars, and fats into fatty acids and glycerol. The water in our food and

drink is also absorbed into the bloodstream to provide the body with the fluid it needs.

How Digestion Works

The digestive system is made up of the alimentary canal (also called the digestive tract) and the

other abdominal organs that play a part in digestion, such as the liver and pancreas. The alimentary

canal is the long tube of organs — including the esophagus, stomach, and intestines — that runs from

the mouth to the anus. An adult's digestive tract is about 30 feet (about 9 meters) long.

Digestion begins in the mouth, well before food reaches the stomach. When we see, smell, taste, or

even imagine a tasty meal, our salivary glands, which are located under the tongue and near the

lower jaw, begin producing saliva. This flow of saliva is set in motion by a brain reflex that's triggered

when we sense food or think about eating. In response to this sensory stimulation, the brain sends

impulses through the nerves that control the salivary glands, telling them to prepare for a meal.

As the teeth tear and chop the food, saliva moistens it for easy swallowing. A digestive enzyme

called amylase, which is found in saliva, starts to break down some of the carbohydrates (starches

and sugars) in the food even before it leaves the mouth.

Swallowing, which is accomplished by muscle movements in the tongue and mouth, moves the food

into the throat, or pharynx. The pharynx, a passageway for food and air, is about 5 inches (12.7

centimeters) long. A flexible flap of tissue called the epiglottisreflexively closes over the windpipe

when we swallow to prevent choking.

From the throat, food travels down a muscular tube in the chest called the esophagus. Waves of

muscle contractions calledperistalsis force food down through the esophagus to the stomach. A

person normally isn't aware of the movements of the esophagus, stomach, and intestine that take

place as food passes through the digestive tract.

At the end of the esophagus, a muscular ring or valve called asphincter allows food to enter the

stomach and then squeezes shut to keep food or fluid from flowing back up into the esophagus. The

stomach muscles churn and mix the food with acids and enzymes, breaking it into much smaller,

digestible pieces. An acidic environment is needed for the digestion that takes place in the stomach.

Glands in the stomach lining produce about 3 quarts (2.8 liters) of these digestive juices each day.

Most substances in the food we eat need further digestion and must travel into the intestine before

being absorbed. When it's empty, an adult's stomach has a volume of one fifth of a cup (1.6 fluid

ounces), but it can expand to hold more than 8 cups (64 fluid ounces) of food after a large meal.

Role of the IntestinesBy the time food is ready to leave the stomach, it has been processed into a thick liquid called chyme.

A walnut-sized muscular valve at the outlet of the stomach called the pylorus keeps chyme in the

stomach until it reaches the right consistency to pass into the small intestine. Chyme is then squirted

down into the small intestine, where digestion of food continues so the body can absorb the nutrients

into the bloodstream.

The small intestine is made up of three parts:

1. the duodenum, the C-shaped first part

2. the jejunum, the coiled midsection

3. the ileum, the final section that leads into the large intestine

The inner wall of the small intestine is covered with millions of microscopic, finger-like projections

called villi. The villi are the vehicles through which nutrients can be absorbed into the body.

The liver (located under the ribcage in the right upper part of the abdomen), the gallbladder (hidden

just below the liver), and thepancreas (beneath the stomach) are not part of the alimentary canal, but

these organs are essential to digestion.

The liver produces bile, which helps the body absorb fat. Bile is stored in the gallbladder until it is

needed. The pancreas produces enzymes that help digest proteins, fats, and carbs. It also makes a

substance that neutralizes stomach acid. These enzymes and bile travel through special channels

(called ducts) directly into the small intestine, where they help to break down food. The liver also plays

a major role in the handling and processing of nutrients, which are carried to the liver in the blood from

the small intestine.

From the small intestine, undigested food (and some water) travels to the large intestine through a

muscular ring or valve that prevents food from returning to the small intestine. By the time food

reaches the large intestine, the work of absorbing nutrients is nearly finished. The large intestine's

main function is to remove water from the undigested matter and form solid waste that can be

excreted.

The large intestine is made up of three parts:

1. The cecum is a pouch at the beginning of the large intestine that joins the small intestine to the

large intestine. This transition area expands in diameter, allowing food to travel from the small

intestine to the large. The appendix, a small, hollow, finger-like pouch, hangs at the end of the

cecum. Doctors believe the appendix is left over from a previous time in human evolution. It no

longer appears to be useful to the digestive process.

2. The colon extends from the cecum up the right side of the abdomen, across the upper abdomen,

and then down the left side of the abdomen, finally connecting to the rectum. The colon has three

parts: the ascending colon; the transverse colon, which absorb fluids and salts; and the descending

colon, which holds the resulting waste. Bacteria in the colon help to digest the remaining food

products.

3. The rectum is where feces are stored until they leave the digestive system through the anus as a

bowel movement.

Digestive System ProblemsNearly everyone has a digestive problem at one time or another. Some conditions, like indigestion or

mild diarrhea, are common; they result in mild discomfort and get better on their own or are easy to

treat. Others, such as inflammatory bowel disease (IBD), can be ongoing and troublesome and should

be discussed with a GI specialist or gastroenterologist (doctors who specialize in the digestive system).

Problems With the Esophagus

Problems affecting the esophagus may be congenital (present at birth) or noncongenital (developed

after birth). Examples include:

Congenital conditions. Tracheoesophageal fistula is a connection between the esophagus and

the trachea (windpipe) where there shouldn't be one. In babies with esophageal atresia, the

esophagus comes to a dead end instead of connecting to the stomach. Both conditions are usually

detected soon after a baby is born — sometimes even before — and require surgery to repair.

Noncongenital conditions. Esophagitis (inflammation of the esophagus) can be caused by

infection, certain medications, orgastroesophageal reflux disease (GERD). With GERD, the

esophageal sphincter (the valve that connects the esophagus with the stomach) doesn't work well

and allows the acidic contents of the stomach to move backward up into the esophagus. GERD

often can be corrected through lifestyle changes, such as dietary adjustments. Sometimes, though,

it requires treatment with medication.

Problems With the Stomach and IntestinesAlmost everyone has experienced diarrhea or constipation. With diarrhea, muscle contractions move

the contents of the intestines along too quickly and there isn't enough time for water to be absorbed

before the feces are pushed out of the body. Constipation is the opposite: The contents of the large

intestines do not move along fast enough and waste materials stay in the large intestine so long that

too much water is removed and the feces become hard.

Other common stomach and intestinal disorders include:

Gastrointestinal infections can be caused by viruses, by bacteria (such as Salmonella, Shigella,

Campylobacter, or E. coli), or by intestinal parasites (such as amebiasis and giardiasis). Abdominal

pain or cramps, diarrhea, and sometimes vomiting are the common symptoms of gastrointestinal

infections. These usually go away on their own without medicines or other treatment.

Appendicitis, an inflammation of the appendix, most often affects kids and teens between 11 and

20 years old, and requires surgery to correct. The classic symptoms of appendicitis are abdominal

pain, fever, loss of appetite, and vomiting.

Gastritis and peptic ulcers arise when a bacterium, Helicobacter pylori, or the chronic use of

drugs or certain medications weakens the protective mucous coating of the stomach and

duodenum, allowing acid to get through to the sensitive lining beneath. This can irritate and

inflame the lining of the stomach (gastritis) or cause peptic ulcers, which are sores or holes in the

lining of the stomach or the duodenum that cause pain or bleeding. Medications usually

successfully treat these conditions.

Inflammatory bowel disease (IBD) is chronic inflammation of the intestines that affects older

kids, teens, and adults. There are two major types: ulcerative colitis, which usually affects just

the rectum and the large intestine; and Crohn's disease, which can affect the whole

gastrointestinal tract from the mouth to the anus as well as other parts of the body. They are

treated with medications and, if necessary, intravenous (IV) feedings to provide nutrition. In some

cases, surgery may be necessary to remove inflamed or damaged areas of the intestine.

Celiac disease is a disorder in which the digestive system is damaged by the response of the

immune system to a protein called gluten, which is found in wheat, rye, and barley and a wide

range of foods, from breakfast cereal to pizza crust. People with celiac disease have difficulty

digesting the nutrients from their food and may experience diarrhea, abdominal pain, bloating,

exhaustion, and even depression when they eat foods with gluten. Symptoms can be managed by

following a gluten-free diet. Celiac disease runs in families and can become active after some sort

of stress, such as surgery or a viral infection. A doctor can diagnose celiac disease with a blood test

and by taking a biopsy of the small intestine.

Irritable bowel syndrome (IBS), a common intestinal disorder, affects the colon and may cause

recurrent abdominal cramps, bloating, constipation, and diarrhea. There is no cure, but IBS

symptoms may be treated by changing eating habits, reducing stress, and making lifestyle

changes. A doctor may also prescribe medications to relieve diarrhea or constipation. No one test is

used to diagnose IBS, but a doctor may identify it based on symptoms, medical history, and a

physical exam.

Problems With the Pancreas, Liver, and Gallbladder

Conditions affecting the pancreas, liver, and gallbladder often affect the ability of these organs to

produce enzymes and other substances that aid in digestion. Examples include:

Cystic fibrosis is a chronic, inherited illness that not only affects the lungs but also causes the

production of abnormally thick mucus to block the ducts or passageways in the pancreas. This

mucus also prevents digestive juices from entering the intestines, making it difficult to properly

digest proteins and fats. This causes important nutrients to pass out of the body unused. To help

manage their digestive problems, people with cystic fibrosis can take digestive enzymes and

nutritional supplements.

Hepatitis, a condition with many different causes, is when the liver becomes inflamed and may

lose its ability to function. Viral hepatitis, such as hepatitis A, B, or C, is highly contagious. Mild

cases of hepatitis A can be treated at home; however, serious cases involving liver damage may

require hospitalization.

The gallbladder can develop gallstones and become inflamed — a condition called cholecystitis.

Although gallbladder conditions are uncommon in kids and teens, they can occur in those who

have sickle cell anemia or are being treated with certain long-term medications.

Keeping Digestion on TrackThe kinds and amounts of food a person eats and how the digestive system processes that food play

key roles in maintaining good health. Eating a healthy diet is the best way to prevent common

digestive problems.

http://science.nationalgeographic.com/science/health-and-human-body/human-body/digestive-system-article/

The digestive system is the series of tubelike organs that convert our meals into body fuel. In all there's about 30 feet (9 meters) of these convoluted pipeworks, starting with the mouth and ending with the anus. Along the way, food is

broken down, sorted, and reprocessed before being circulated around the body to nourish and replace cells and supply energy to our muscles.

Food on the plate needs to become a mashed-up, gooey liquid for the digestive system to be able to split it up into its constituent parts: proteins, carbohydrates, fats, vitamins, and minerals. Our teeth start the process by chewing and grinding up each mouthful, while the tongue works it into a ball-shaped bolus for swallowing.

Moistening saliva fed into the mouth from nearby glands starts the process of chemical digestion using specialized proteins called enzymes. Secreted at various points along the digestive tract, enzymes break down large molecules of food into smaller molecules that the body is able to absorb.

Once we swallow, digestion becomes involuntary. Food passes down the throat to the esophagus, the first of a succession of hollow organs that transport their contents through muscular contractions known as peristalsis.

The esophagus empties into the stomach, a large, muscular chamber that mixes food up with digestive juices including the enzymes pepsin, which targets proteins, and lipase, which works on fats. Hydrochloric acid likewise helps to dissolve the stomach contents while killing potentially harmful bacteria. The resulting semifluid paste—chyme—is sealed in the stomach by two ringlike sphincter muscles for several hours and then released in short bursts into theduodenum.

The first of three sections of the small intestine, the duodenum produces large quantities of mucus to protect the intestinal lining from acid in the chyme. Measuring about 20 feet (6 meters) in length, the small intestine is where the major digestion and absorption of nutrients take place. These nutrients are taken into the bloodstream, via millions of tiny, fingerlike projections called villi, and transported to the liver.

What's left in the digestive tract passes into the large intestine, where it's eaten by billions of harmless bacteria and mixed with dead cells to form solid feces. Water is reabsorbed into the body while the feces are moved into the rectum to await expulsion.

Key Players

Other organs that play a key role in digestion include the liver, gallbladder, and pancreas. The pancreas is a gland organ located behind the stomach that manufactures a cocktail of enzymes that are pumped into the duodenum. A duct also connects the duodenum to the gallbladder. This pear-shaped sac squeezes out green-brown bile, a waste product collected from the liver that contains acids for dissolving fatty matter.

The liver itself is the body's main chemical factory, performing hundreds of different functions. It processes nutrients absorbed into the blood by the small intestine, creating energy-giving glycogen from sugary carbohydrates and converting dietary proteins into new proteins needed for our blood. These are then stored or released as needed, as are essential vitamins and minerals. The liver also breaks down unwanted chemicals, such as any alcohol consumed, which is detoxified and passed from the body as waste.