|MadSci Network: Medicine|
Hello, Aung. Exact timelines of the absorption of carbohydrates are difficult to pinpoint as many variables exist. For example, the smaller the stomach, the more rapidly it empties, or how well the food is cooked and/or chewed, to whether it's a solid or liquid, and the amount of fiber or fat along with the carbs., as well as stress levels and one's physical condition can all influence the transit time and absorption of carbohydrates. However I'll try to clarify it somewhat for you. Carbs. actually begin their breakdown in the mouth. It takes about 12 seconds for food to reach the stomach. Fluids can reach the stomach in as litle as 1 second. Food stays in the stomach on average about 4 hours, but can range from one to six hours depending on the meal. (A light meal can be emptied after one hour). Carbs. get preferential treatment because they are emptied ahead of other nutrients. The end products of carbohydrate metabolism are called monosaccharides, or simple sugar. Once food reaches the small intestine, digestion proceeds rapidly. A meal stays in the small intestine an average of 4 1/2 hours, but can range between 2 1/2 to 8 hours. So it would take a minimum of about 2 hours, (give or take 30 minutes), from the time you've begun eating until the absorption of carbohydrates. This estimate could easily be double, i.e. at least 4 hours, depending on what else is being consumed along with the carbohydrates. Also, keep in mind that digestion of an entire meal can take between 5 to 9 hours, prior to absorption. There are special circumstances where sugar is absorbed far more quickly, For example, a standard test known as the glucose tolerance test is given to challenge the body's response to dietary glucose. This helps establish one's status or risk towards the development of diabetes. Glucose is administered in a liquid form after a fast of 12 hours. Blood sugar is checked prior to drinking the glucose in order to establish a baseline, and then blood samples are subsequently withdrawn at regular intervals to be analyzed and compared to normal nondiabetic values. Certainly, after 30 minutes blood glucose levels have shot up 50 to 60 mg/100ml. in a normal nondiabetic individual. The effects of consuming the sweetened based drink actually begins to affect glucose levels after only 5 minutes! Keep in mind though, that this test is done with a liquid, on an empty stomach, after a fast, all of which will speed glucose into the intestine for immediate absorption. Another example is seen with hypoglycemics, a condition of low blood sugar. "Following oral administration of 10 to 20 grams of dextrose, increases in blood glucose usually occur within 10 to 20 minutes and peak at about 40 minutes. In one study following oral administration of a 20 gram dose of dextrose as tablets, mean blood glucose concentration increased by 32 mg./Dl 20 minutes later in hypoglycemic patients." (1.) So as you see, there are may different factors that can affect the timing of the absorption of carbohydrates into the bloodstream, but I hope I've given you a better idea. Your mad scientist, Peter Bosani. References: (1.) American Hospital Formulary Service Drug Information - 1985. Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health - Miller. Keane Food, Nutrition and Diet Thereapy - Krause
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