1. Carbohydrates Iva Řehová

2. 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

3. 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...

4. 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.

5. 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).

6. 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.

7. 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.

8. 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 everyone’s 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.

9. Different sugars don’t 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. SugarSweetness fructose173% sucrose100% glucose74% maltose33% galactose33% lactose16% 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.

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

11. Fiber it‘s 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.

12. 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).

13. 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.

14. Glycogen, or animal starch, is formed by glucose molecules. It isn’t present to any large extent in the foods we eat.

15. 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 less Medium GI = 56 - 69 High GI = 70 or more

16. 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.

17. 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.

19. 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/

20. 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

21. 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.

22. 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.