Carbohydrates

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Carbohydrates
Iva Rehová
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• Carbohydrates are defined as sugars and their
  derivatives.
• Carbohydrates play a major role in supplying
  energy for bodily function.
• Carbohydrates, which are stored in limited
  amounts as blood glucose, liver glycogen, and
  muscle glycogen, serve
• as a major source of energy,
• to spare the breakdown of proteins,
• as a metabolic primer for fat metabolism,
• and as a fuel for the central nervous system

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• Well-balanced diet contains about 60 of daily
  calories as carbohydrates, predominantly in
  unrefined, complex form.
• Excellent sources are
• rice, bread, pita bread, whole wheat spaghetti,
  cereals, potatoes, legumes...

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Legumes are full of complex carbohydrates,
proteins, fiber and vitamins and minerals. There
are a lot of polysaccharides resistant to human
digestive enzymes in legumes (lens, beans..).
Consummation of legumes should lead to a
digestive problem (flatulence or diarrhoea).

• This polysaccharides are soluble in water and you
  can reduce amount of them by macerating in water
  for 1 day or by sprouting.

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• Simple sugar consists of a chain of three to
  seven carbon atoms with hydrogen and oxygen
  attached in a ratio of 2 to 1.
• There are three kinds of carbohydrates
• monosaccharides (sugars such as glucose,
  fructose, and galactose)
• disaccharides (sucrose, lactose, and maltose)
• and polysaccharides (starch, fiber, and
  glycogen).

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Monosaccharides

• Glucose the most common simple sugar, also
  called dextrose or blood sugar
• Sources honey, fruits
• Fructose fruit sugar, is the sweetest of the
  sugars
• Sources honey, fruits
• Galactose is produced in the mammary glands of
  lacting animal
• Sources in milk as a part of lactose
• Glucose is an important form of usable food
  energy and the body easily convert both fructose
  and galactose to glucose.

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Disaccharides

• The combination of two monosaccharides makes a
  disaccharide.
• Lactose is formed from glucose galactose
  (enzyme lactase breaks down lactose)
• Sources milk
• Sucrose is formed from glucose fructose
  (enzyme sucrase)
• Sources sugar beets, sugar cane
• Maltose is composed of glucose glucose
  (enzyme maltase)
• Sources germinated grain, they are formed in
  digestive breakdown of large carbohydrate
  molecule
• The monosaccharides and disaccharides
  collectively make up what are commonly referred
  to as the simple sugars.

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Lactose intolerance

• In about 25 of people, intestinal level of the
  enzyme lactase decrease when they get older.
  Occurrence of this intolerance is common among
  African-American and Hispanic people.
• They are unable to digest the lactose in dairy
  products.
• This undigested lactose passes through their
  digestive tract until it is eventually fermented
  by the bacteria that normally live in everyones
  large intestines.
• When this happens it often produces gas, and
  may cause the person to have cramps and other
  unpleasant symptoms. These people are called
  lactose intolerant (this is different than an
  allergy).
• Some of these people may be able to eat yogurt,
  cheese, or other dairy products in which bacteria
  have already broken down the lactose.

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• Different sugars dont all taste the same.
• Some taste more or less sweet than each other.
• For example fructose is almost twice as sweet as
  sucrose.
• The main health benefit in fructose-sweetened
  products is that they contained less sugar.

Some people have been critical of dairy products
containing extra powdered milk (non-fat milk
solids) because of the fact that lactose is so
un-sweet that a person could consume larger
amounts without a lot of sweet taste to warn of
its presence.
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Polysaccharides

• The term polysaccharides is used when three or
  more sugar molecules combine.
• The most common polysaccharides are starch,
  fiber, and glycogen.
• Starch
• its a plant polysaccharide
• Sources grains, pastries, bread, corn, beans,
  peas, potatoes...

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• Fiber
• its a plant polysaccharide too
• The most common fiber are cellulose,
  hemicellulose, lignins, pectins, and gums.
• Fiber is resistant to digestive enzymes and hence
  leaves some residue in the digestive tract.
• There are two categories of dietary fiber
• water soluble
• water insoluble
• Water soluble fiber (pectin, guar gum, inulin)
  presents in oats, rye, beans and other legumes,
  pulp of fruits and vegetables
• This kind of fiber hold water in digestive tract
  and this moisture expansion gives feeling of
  saturation,
• depress absorption and synthesis of cholesterol
  in the gut,
• depress absorption of carbohydrates,
• help in defecation.

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• Water insoluble fiber (cellulose, hemicellulose,
  lignin) presents in brown rice, corn, wheat bran
  (outer layer of the whole grain), peelings of
  fruits and vegetables
• Increasing stool weight and volume
• Mechanically clean the small and large intestines
  to prevent cancer
• Take energy for bacteria in the large intestine.
  This bacteria product short chains of fatty acids
  who take energy for function of intestines
  cells.
• Some plant fibers are both water soluble and
  water insoluble, such as psyllium.
• Some plant have both types of fibers e.g. apple
  pulp is good source of soluble fiber (pectin) and
  apple peel is full of insoluble fiber
  (cellulose).

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• The recommended fiber intake is about 20 to 35 g
  a day.
• Eating a variety of plant food will insure that
  all types of fibers are consumed.
• The ratio of insoluble and soluble should be
  about 3 to 1 and should be derived from foods,
  not from synthetic fiber supplement.
• An excess of dietary fibers carries the risk of
  intestinal distress, and decreases absorption of
  the minerals and vitamins.

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• Glycogen, or animal starch, is formed by glucose
  molecules. It isnt present to any large extent
  in the foods we eat.

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Glycemic index (GI)

• The GI is a measure of the power of foods (or
  specifically the carbohydrate in a food) to raise
  glucose levels after being eaten.
• Foods with a high GI score contain rapidly
  digested carbohydrate, which produces a large
  rapid rise and fall in the level of blood
  glucose.
• In contrast, foods with a low GI score contain
  slowly digested carbohydrate, which produces a
  gradual, relatively low rise in the level of
  blood glucose.
• In particular, foods containing high amounts of
  refined sugars have a high GI.
• Foods with a high GI will lead rapidly to
  hyperglycemia, which will cause a
  hyperinsulinemia, which will cause a reactive
  hypoglycemia (fatigue, hungry, inceasing of food
  intake).
• On the other hand, foods high in fiber generally
  have a low GI.

Low GI 55 or lessMedium GI 56 - 69High GI
70 or more
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• Other factors that influence how quickly the
  carbohydrates in food raise blood sugar include
• Fiber content. Fiber shields the starchy
  carbohydrates in food immediate and rapid attack
  by digestive enzymes. This slows the release of
  sugar molecules into the bloodstream.
• Ripeness. Ripe fruits and vegetables tend to have
  more sugar than unripe ones, and so tend to have
  a higher glycemic index.
• Type of starch. Starch comes in many different
  configurations. Some are easier to break into
  sugar molecules than others. The starch in
  potatoes, for example, is digested and absorbed
  into the bloodstream relatively quickly.
• Fat content and acid content. The more fat or
  acid a food contains, the slower its
  carbohydrates are converted to sugar and absorbed
  into the bloodstream.
• Physical form. Finely ground grain is more
  rapidly digested, and so has a higher GI, than
  more coarsely ground grain, mashed potatoes have
  higher GI than potatoes boiled in their peals.
• All these elements lead to sometimes
  counterintuitive results. Some foods that contain
  complex carbohydrates, such as potatoes, quickly
  raise blood sugar levels, while some foods that
  contain simple carbohydrates, such as whole
  fruit, raise blood sugar levels more slowly.

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Measuring the Glycemic Index of Foods

• To determine the glycemic index of a food,
  volunteers are typically given a test food that
  provides 50 grams of carbohydrate and a control
  food (white bread or pure glucose) that provides
  the same amount of carbohydrate on different
  days.
• Blood samples for the determination of glucose
  are taken prior to eating and at regular
  intervals after eating over the next several
  hours.
• The changes in blood glucose over time are
  plotted as a curve.
• The glycemic index is calculated as the area
  under the glucose curve after the test food is
  eaten, divided by the corresponding area after
  the control food is eaten.
• The value is multiplied by 100 to represent a
  percentage of the control food.

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• Low GI diets help people lose and control weight
• Low GI diets increase the body's sensitivity to
  insulin
• Low GI carbs improve diabetes control
• Low GI carbs reduce the risk of heart disease
• Low GI carbs reduce blood cholesterol levels
• Low GI carbs can help you manage the symptoms of
  premenstrual syndrom.
• Low GI carbs reduce hunger and keep you fuller
  for longer
• Low GI carbs prolong physical endurance
• High GI carbs help re-fuel carbohydrate stores
  after exercise muscle glycogen.
• a useful address http//www.glycemicindex.com/

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Glycemic load

• Glycemic Index alone does not provide enough
  information about the glycemic affect of a food.
• For instance a carrot is high on GI, but you
  would have to eat pounds of this vegetable to
  have any affect on blood glucose. This is due to
  that the amount of carbs in a carrot is very
  small.
• To calculate glycemic load - multiply the GI by
  the amount of carbohydrate and divide by 100.
• For example
• an 100g serve of carrot with a GI of 92 has 4.2
  g per serve.
• 92 x 4.2 / 100 3.9
• an 100g serve of water melon with a GI of 72 has
  5,6 g per serve.
• 72 x 5,6/100 GL 4
• Foods with a low GI usually have a low GL.
• Low GL 10 or less Medium GI 11-19 High
  GI 20 or more

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Digestion and absorption

• The mouth the enzyme of salivary amylase attacks
  starch and begins to reduce it to the simpler
  disaccharide form..
• The small intestine pancreatic amylase, in
  conjunction with other enzymes, completes the
  breakdown of starch into simple monosaccharides.
• Monosaccharides are absorbed from the small
  intestine into bloodstream and are transported to
  the hepatic-portal vein, which feeds directly to
  the liver.
• The colon is the final stop for undigested
  carbohydrates, including fibrous substances.
• The stool consists of undigested fragments of
  plant fiber and connective tissue from animal
  foods, plus bacteria and water.

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• Most ingested carbohydrates are initially
  converted into blood glucose and used for energy
  or stored as liver and muscle glycogen, but
  excess carbohydrates may be converted into fat.
• The body can make glucose from certain
  by-products of protein and fat.