Fiber, dietary complex carbohydrates

The food fiavorist also must be aware of metal complexes, which carbohydrates are capable of forming, Iron salts not only form complexes with dietary fiber, but with nearly all of the known natural sugars. Fructose, maltitol. sorbitol, and xylitol can easily form complexes with the ferric... 

There are several aspects of diabetic dietary management which have not been covered in this chapter salt intake and the effect of carbohydrate and fiber on blood coagulation, minerals, and trace elements are examples. It is important to remember that a benefit from change in diet can be offset by other unforeseen effects. There are, however, no known detrimental effects attributable to the consumption of mixed Western diets rich in complex carbohydrate and fiber. The optimum proportion of calories to be taken as carbohydrate remains open to question. The British Diabetic Association has suggested 50-55%, and some studies have shown benefit when even greater quantities of carbohydrate have been used. For practical purposes, a 50% proportion seems a sensible aim, but it must be remembered that while this figure represents a considerable increase for most diabetics, all the studies cited in this chapter have involved a higher proportion of calories from carbohydrate. 

Fiber Dietary fiber is defined as the nondigestible carbohydrates and lignin (a complex polymer of phenylpropanoid subunits) pres ent in plants. Several different terms are used to described this complex group of compounds. For example, functional fiber is the... 

Most scientists and organizations have suggested an increase in complex carbohydrate intake (some have also emphasized dietary fiber), with a concommitant decrease in simple sugars. These... 

Most aspects t>f carbohydrate nutrition are simpler than those of other nutrients, (For example, fat nutrition is complicated by the fact that the metabolism of fats requires bile salts to maintain solubility during digestion and lipoproteins and albumin during distribution in the body.) On the other hand, the nutrition of the carbohydrates that take the form of dietary fibers is very complicated. This complexity . > due to the fact that they arc metabolized by enzymes of the gut microflora. 

Complex carbohydrates are better for us than the simple sugars. Starch, found in rice, potatoes, breads, and cereals, is an excellent energy source. In addition, the complex carbohydrates, such as cellulose, provide us with an important supply of dietary fiber. 

Decreased fat intake, particularly saturated fat intake, is clearly linked to decreased serum cholesterol levels and decreased prevalence of CV comphcations, such as CAD. Although recent studies place some doubt on the contribution of fat intake toward increasing the risk of breast cancer, high levels of fat intake are still associated with the risk of some cancers, and perhaps type n diabetes. Foods rich in other dietary components, including fiber, complex carbohydrates. 

Despite the fact that a plethora of dietary factors could, and will, affect the absorption characteristics of phytochemicals, this area has not been systematically explored. One reason might be the complexity of dietary factors and their interactions that could affect absorption. A nonexhaustive list would include the volume and composition of the food consumed, pH, caloric density, viscosity, nutrients (carbohydrates, protein, fat, fibers), alcohol, caffeine, and the presence of other phytochemicals. Such dietary factors affect the functional status, motility, and acidity of the gastrointestinal tract in a complex manner and modify the physicochemical properties, formulation, and dissolution characteristics of the compound of interest. Calcium in dairy products, for example, has the potential to chelate tetracyclines and fluoroquinolones and, thereby, reduce their bioavailability and biological activity [31]. 

Because of the variety of polysaccharides which can be fermented by some Bacteroides species, it is difficult to predict with certainty which polysaccharides in the complex mixture of dietary and host-produced carbohydrates that enter the colon will be degraded most rapidly and most extensively. Further information about how these organisms make choices between different polysaccharides i vitro may help to clarify this issue. However, nutritionists who are interested in catabolism of dietary fiber components iji vivo should be aware that the bacteria may prefer other sources of carbohydrate, such as mucopolysaccharides from host secretions or even Maillard products, to the dietary polysaccharide under study, and that this preference may influence catabolism of a particular polysaccharide in ways which we cannot at present predict. Effects of this sort may be responsible for some of the individual-to-individual variation which is encountered in nutritional studies of dietary fiber utilization. 

It is my hope and belief that this publication will help in the expansion and utilization of fiber sources in foods, as well as in pharmaceutical and medical preparations. After all, we should recognize that the chance to accomplish this is quite favorable because complex carbohydrates, which are the main constituents of dietary fiber, represent the only group of major food components for which increased daily intake is repeatedly being recommended. 

Dietary carbohydrates are often classified as simple or complex. Simple carbohydrates are the sugars we classified earlier as monosaccharides and disaccharides (Chapter 7). Complex carbohydrates consist essentially of the polysaccharides amylose and amylo-pectin, which are collectively called starch. Cellnlose, another polysaccharide, is also a complex carbohydrate however, becanse it cannot be digested by hnmans, it serves a non-nntritive role as fiber. 

There are three chemical compounds that form the building blocks of food carbohydrates, hits (or hpids), and proteins. Carbohydrate molecules, which are found in fruits, vegetables, starches, and dairy products, consist of atoms of carbon, hydrogen, and oxygen, chemically bonded in a ratio of 1 2 1. Monosaccharides and disaccharides such as glucose, fructose, and sucrose have just one or two molecules of this kind and are known as simple sugars. Polysaccharides like starch, glycogen, and cellulose (an important component of dietary fiber) have several carbohydrate molecules and are known as complex... 

Henshall, A., High-performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) A powerful tool for the analysis of dietary fiber and complex carbohydrates. Complex Carbohydrates in Foods, Cho, S.S., Prosky, L., and Dreher, M. (Eds.), Marcel Dekker, Inc., New York, p. 267, 1999. 

An obvious factor for the inconsistent results of the effect of different intakes of dietary fiber on colorectal cancer is the variation in the analytical methodology used in different studies. There is also increasing evidence that total dietary complex carbohydrates may be as important as fiber. Analysis of stool weight from 20 populations in 12 countries showed that larger stools were correlated with a lower incidence of colon cancer. Intakes of starch and dietary fiber (rather than fiber alone) were the best dietary correlates with stool weight. A subsequent meta-analysis showed that greater consumption of starch (but not of NSPs) was associated with low risk of colorectal cancer in 12 populations. The examination also showed that fat and protein intakes correlated positively with risk. This meta-analysis is probably the first of its kind to... 

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