Dietary protein, source

Nutrient analysis of stabilized rice bran and its derivatives indicates that it is a good source of protein, dietary fiber and carbohydrates, in addition to several valuable phytonutrients, antioxidants, vitamins and minerals (Table 17.1). SRB and its water-soluble and water-insoluble derivatives contain all the nutrients at different levels. They are gluten and lactose free and do not give rise to any food allergy. 

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. 

Soybeans (Glycine max) are protein-rich legumes widely grown around the world as a food crop. They are the major dietary source of isoflavones, which are broken down in the intestine into the phytoestrogens genis-... 

Vitamin B12 consists of a porphyrin-like ring with a central cobalt atom attached to a nucleotide. Various organic groups may be covalently bound to the cobalt atom, forming different cobalamins. Deoxyadenosylcobalamin and methylcobalamin are the active forms of the vitamin in humans. Cyanocobalamin and hydroxocobalamin (both available for therapeutic use) and other cobalamins found in food sources are converted to the active forms. The ultimate source of vitamin Bi2 is from microbial synthesis the vitamin is not synthesized by animals or plants. The chief dietary source of vitamin Bi2 is microbially derived vitamin B12 in meat (especially liver), eggs, and dairy products. Vitamin Bi2 is sometimes called extrinsic factor to differentiate it from intrinsic factor, a protein normally secreted by the stomach that is required for gastrointestinal uptake of dietary vitamin B12. 

The anticancer effect of soy, the only relevant dietary source of isoflavones and the main candidate foodstuff responsible for the cancer protection conferred by Asian diets, has been tested in a number of animal studies. Messina et al. [204] reviewed 26 such studies published up to 1994 (gastrointestinal and non gastrointestinal). Seventeen of them (65%) reported a protective effect and none found a potentiation of carcinogenesis. One study has examined the effect of feeding a soy protein diet in a genetic... 

Citrus juices and their products cannot be considered significant dietary sources of protein because the protein efficiency ratio (PER) of citrus protein is less than 20% that of casein (23, 41). 

Arachidonic acid (5,8,11,14-eicosatetraenoic acid), a polyunsaturated fatty acid derived from dietary sources or by desaturation and chain elongation of the essential fatty acid linoleic acid, is found widely in the body. It is transported in a protein-bound state and stored in the phospholipids of cell membranes in all tissues of the body [108] from where it can be changed into biologically... 

Cholesterol is an essential component of cellular membranes. In addition to dietary sources, we can also synthesize cholesterol. Cholesterol is transported in the blood as a lipoprotein, which is an aggregate of water-soluble proteins, cholesterol, and other lipids, including triglycerides. Proteins are denser than lipids,... 

Figure 3.2 Amino acids that occur in proteins. Those marked with an asterisk cannot be synthesized by the human body and must come from dietary sources.

Nutritional significance. As one of the major whey proteins in human milk and also relatively abundant in bovine colostrum, LF is of interest as a dietary source of amino acids as well as for the bioavailability of iron. LF has an... 

It is clear from this discussion that carnitine is required in humans for the oxidation of long-chain fatty acids. In humans, carnitine is derived from both dietary sources and endogenous biosynthesis. Meat products, particularly red meats, and dairy products are important dietary sources of carnitine. Since biosynthesis can meet all physiological requirements, carnitine is not an essential nutrient. Premature infants are an exception to this rule as they lack a mature biosynthetic system and have limited tissue carnitine stores. As many infant formulas, particularly those based on soy protein, are low in carnitine, premature infants receiving a significant part of their nutrition from such formulas may be susceptible to carnitine deficiency. 

Fats and oils have major roles in human nutrition. They are concentrated dietary sources of energy, providing approximately 9 kcal/g when metabolized compared with 4 kcal/g for carbohydrates and proteins, and account for about 36 percent of domestic caloric intake per capita.19 Dietary lipids also can provide essential molecular structures that are synthesized by the body into compounds required for selective functioning of cell membranes and regulation of life processes. 

---