It is important to note that the metabolism of fructose involves many regulated reactions and its fate may vary depending on nutrients consumed simultaneously with fructose e. Acute metabolic fate of fructose in the body within 6 hours of ingesting grams about teaspoons of fructose adapted from Sun et al. A number of factors affect carbohydrate digestion and absorption, such as the food matrix and other foods eaten at the same time 7. Foods with a high GI are more quickly digested, and cause a larger increase in blood glucose level compared to foods with a low GI.
Foods with a low GI are digested more slowly and do not raise blood glucose as high, or as quickly, as high GI foods. Examples of factors that affect carbohydrate absorption are described in the table below:. Less processed foods, such as slow cooking oats or brown rice, have a lower GI than more processed foods such as instant oats or instant rice. Pasta cooked 'al dente' tender yet firm has a lower GI than pasta cooked until very tender.
Use of Dietary Carbohydrates as Energy. Glucose is the primary energy source of the body. Major dietary sources of glucose include starches and sugars. Digestion of Carbohydrates. The digestion and absorption of dietary carbohydrates can be influenced by many factors. Absorption of Carbohydrates. Genetic Modification 4: Ecology 1.
Energy Flow 3. Carbon Cycling 4. Climate Change 5: Evolution 1. Evolution Evidence 2. Natural Selection 3. Classification 4. Cladistics 6: Human Physiology 1. Digestion 2. The Blood System 3. Disease Defences 4. Gas Exchange 5. Homeostasis Higher Level 7: Nucleic Acids 1.
DNA Structure 2. Transcription 3. Translation 8: Metabolism 1. Metabolism 2. Cell Respiration 3. Carbohydrates, abundantly present in foods such as breads, cereals, fruits and vegetables, are the main source of energy in a diet.
During digestion, a series of enzymatic reactions break down the carbohydrates in these foods into simple carbohydrates that are easily absorbed in the small intestine. While complex carbohydrates require enzymes such as salivary amylase, pancreatic amylase and maltose for digestion, simple carbohydrates require little or no enzymatic reaction before absorption. Different forms of carbohydrates are present in foods. Individual units of sugar such as glucose, fructose and galactose are the simplest forms of carbohydrates called monosaccharides, while sucrose, lactose and maltose are disaccharides made up of two monosaccharides linked together.
Complex carbohydrates include starch and fiber, which are polysaccharides made up of long chains of glucose units bonded together. Although fiber resists enzyme action and is not broken down during digestion, break down of starch by enzymes starts in the mouth. Chewing breaks food into small molecules that combine with saliva secreted by the salivary glands in the mouth.
Along with mucin and buffers, saliva contains the enzyme salivary amylase, which acts on the starch in food and breaks it down to maltose. Salivary amylase continues for the short duration that the carbohydrates are in the mouth, after which the mixture of the partially digested carbohydrates travels down the esophagus into the stomach. Due to the inhibition of salivary amylase activity by the acidic gastric juices, digestion of carbohydrates does not occur in the stomach.
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