Proteins caloric yield

Foods that yield in the range of 5-10 calories/g protein should be excellent dietary sources of protein. However, those that yield 50-100 or more calories/g protein should probably be used more where calories for energy are needed and supplemented with other protein sources. In many countries man has supplemented his diet with protein by the consumption of animal products and meat in order to eliminate this problem and balance the protein-caloric values. 

Triacylglycerols are highly concentrated stores of metaholic energy because they are reduced and anhydrous. The yield from the complete oxidation of fatty acids is about 9 kcal g" (38 kJ g- ), in contrast with about 4 kcal g l (17 kJ g-i) for carbohydrates and proteins. The basis of this large difference in caloric yield is that fatty acids are much more reduced. Furthermore, triacylglycerols are nonpolar, and so they are stored in a nearly anhydrous form, whereas much more polar proteins and carbohydrates are more highly hydrated. In fact, 1 g of dry glycogen binds about 2 g of water. 

It may be seen from Fig. G-21 that potatoes outstrip by far the caloric yields of the leading grains, whereas soybeans, corn, and potatoes each provide more protein per acre than either rice or wheat. Unfortunately, the merits of the potato are not appreciated fully by much of the world, as evidenced by the fact that most of this crop is grown in the region of Europe which extends from Ireland to the Soviet Union. 

Rice is grown in more than 100 countries and on every continent except Antarctica. In the world economy rice is an extremely important food, second only to wheat in total world production, and its yield per hectare exceeds that of wheat (57). Rice is the main staple food for more than half of the world s population and it accounts for one-third to one-half of the daily caloric intake in many Asian countries. It is also the major source of protein for the masses of Asian people. In many African and South American countries rice is rapidly becoming the staple food for much of the population. 

Those with a normal diet take in food in the forms of carbohydrates, fats and proteins. Because it has a low water content and produces so many ATP molecules, fat yields 9.3 Calories per gram while carbohydrates and proteins yield less than half as much (4.1 and 4.3 calorics per gi-am respectively). Thus, we get a huge number of calories from a small quantity of fat eaten. The average person in the United States has a diet with 50 percent of the calories in the form of carbohydrates, 35 percent in the form of fat and 15 percent in the form of protein. We need about 1 gram of protein per kilogram of body weight per day to replace body proteins that are broken down. A 70 kg person... 

When oxidized, 1 g of protein yields four calories. Including the caloric contribution from protein in calorie calculations is controversial therefore, PN calories can be calculated as either total or nonprotein calories. 

Food is "burned" in the body to yield H20, C02, and energy, just as natural gas or coal is burned in a furnace to yield the same products. In fact, the "caloric value" of a food is just the heat of reaction, AH0, for complete combustion of the food (minus a small correction factor). The value is the same whether the food is burned in the body or in a laboratory calorimeter. One gram of protein releases 17 kj (4 kcal), 1 g of carbohydrate releases 17 kj, and 1 g of fat releases 38 kj. As shown in Table 8.4, which gives the caloric value of some common foods, data are usually given in Calories (note the capital C), where 1 Cal = 1000 cal = 1 kcal = 4.184 kj. 

Evaluation of our data by multiple logistic analyses consistently yielded statistically significant positive associations of caloric consumption, controlled for protein and fat intake, with the incidence of tumors. The odds of developing an adenocarcinoma, adenoma or tumor type increased by a factor of 1.10, 1.14 and 1.09, respectively, for each 1-kcal increase in intake. The effect of calories can be visualized by dividing the 351 rats into thirds... 

Protein in PN solutions is provided in the form of crystalline amino acids (CAAs), which are used primarily for protein synthesis. When oxidized for energy, 1 g of protein yields 4 calories. However, including the caloric contribution from protein when calculating calories provided by the PN regimen is controversial. ... 

From the role of tryptophan in the biosynthesis of nicotinic acid, it is obvious that the nutritional studies on nicotinic acid deficiency must take tryptophan intake into account. Indeed, 60 mg of tryptophan in the diet is as effective as 1 mg of nicotinic acid. Since 70 g of protein yields 720 mg of tryptophan, the intake of such an amount of protein corresponds to 12 mg of nicotinic acid in preventing niacin deficiency. Since the requirements for niacin, like those of thiamine, depend essentially on the caloric intake, it is useful to express the requirements in niacin equivalents per 1000 calories. The optimum requirement is 4.4 mg niacin per 1000 calories. 

The tamarind fruit that is grown in upper Egypt is brewed into a popular soft drink. The oil yield and fatty acid composition were very different from the Indian tamarind. The seeds contain 16.25% oil with a composition that is high in linoleic, oleic and lauric acids (Table 5.11). Lesser amounts of stearic and linolenic were present. The tamarind seed meal was also low in protein (2.66%) compared to other oil seeds (cottonseed, peanut) but does contain a substantial amount of sugar (25.28%) which would give the meal a high caloric value if used as an animal feed (Morad et al., 1978). 

In formulation of diets to meet energy requirements, proteins and carbohydrates are considered to yield 4 cal. per gram, and fats, 9 cal. per gram. The specific dynamic action of foodstuffs must also be considered and is usually calculated as 6 % of the total caloric value of the food over a 24-hr. period.2 ... 

The caloric contents of diets are usually calculated by the use of Atwater caloric conversion factors which were derived for the mixed diets consumed by Americans around the turn of the century. These factors are based upon the assumptions that each gram of carbohydrate, fat, and protein in the diet will yield 4, 9, and 4 Calories (kcal), respectively. However, the Atwater factors were not intended to be used for single foods or for mixed diets that differed markedly in composition from those for which they were derived. Today, there are a wide variety of diets that have been drastically modified from the average American dietary pattern. Therefore, it is important that dietary planners understand the basic principles of food calorimetry. 

The average caloric value of each of three major nutrients is known as its fuel factor. One gram of catbobiydratB yields 4 calories, 1 g of fat yields 9 calories, and 1 g of protein yields 4 calories. 

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