Glucose caloric value

It would seem that normally the oxidation of ketone bodies would proceed largely to completion in the liver by the ketolytic mechanism. Whenever the supply of carbohydrates here is sufficiently reduced, appreciable amounts of ketones then escape oxidation and pass into the blood. When the concentration of ketones becomes sufficiently elevated, a ketonuria occurs and also some ketones will be utilized by the tissues. Such a theory would largely limit the ketolysis mechanism to the liver. It would explain the specificity of the sugars in preventing ketonuria and the discrepancy between the amount of D-glucose required to prevent ketosis and the caloric value of the fat spared. It is further supported by the demonstration that the liver is capable of exhibiting ketolysis. 

Unlike most crops that store carbon as starch, a polymer of glucose, in the Jerusalem artichoke carbon is stored as inulin, a fructose polymer. The implications of this have a pronounced influence on the value and utility of the crop. An extremely important attribute derived from inulin is its nutritional contributions, even though the caloric value in humans is low. The evidence for the role of inulin in decreasing blood cholesterol and in enhancing other positive health benefits has been firmly established. 

Sorbitol is widely used in a number of pharmaceutical products and occurs naturally in many edible fruits and berries. It is absorbed more slowly from the gastrointestinal tract than sucrose and is metabolized in the liver to fructose and glucose. Its caloric value is approximately 16.7J/g (4cal/g). Sorbitol is better tolerated by diabetics than sucrose and is widely used in many sugar-free liquid vehicles. However, it is not considered to be unconditionally safe for diabetics. 

Because it has no caloric value, when it became commercially available in 1885, saccharin became an important substitute for sucrose. The chief nutritional problem in the West was—and still is—the overconsumption of sugar and its consequences obesity, heart disease, and dental decay. Saccharin is also important to diabetics, who must limit their consumption of sucrose and glucose. Although the toxicity of saccharin was not studied carefully when the compound first became available to the public (our current concern with toxicity is a fairly recent development), extensive studies done since... 

The caloric value of a food is directly related to its oxidation state, which is a measure of AG° for transfer of electrons from that fuel to O2. The electrons donated by the fuel are from its C-H and C-C bonds. Fatty acids such as palmitate (CH3(CH2)i4COOH) have a caloric value of roughly 9 kcal/g. Glucose is already partially oxidized and has a caloric value of only about 4 kcal/g. The carbons, on an average, contain fewer C-H bonds from which to donate electrons. 

The energy content of foodstuffs varies. The approximate caloric content of generic carbohydrates, fats, and proteins are listed in Table 23-1. These values are based on a varied diet, i.e., all components are present. Recall that humans cannot synthesize glucose from fat. In the absence of carbohydrates, therefore, fat metabolism becomes inefficient, and the caloric value of fat decreases. 

If cellulose does not provide fuel value, we must conclude that it is not converted in the body into CO2 and H2O, as starch is. A slight but critical difference in the structures of starch and cellulose explains why only starch is broken down into glucose in the body. Cellulose passes through without undergoing significant chemical change. It serves as fiber, or roughage, in the diet but provides no caloric value. 

Another disadvantage is supposed to be the caloric value that diabetics have to take into account. However, with the increased use of blood glucose monitors and relatively simple insulin delivery devices it has become easier to match the carbohydrate intake to the blood sugar level, especially for patients with type I diabetes. Apart from that the contribution of sugar through medicines is small and it is actually not necessary to develop special sugar-free medicines for diabetics. 

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