Dietary components/constituents

Metabolism of pectin. Pectin has only recently come, to be considered a part of the dietary fiber complex. Previously it was excluded because 1) it is not fibrous (except at the molecular level), 2) it escapes detection in standard fiber tests owing to its solubility, and 3) it usually does not survive intestinal passage. In a reassessment of which dietary components should be considered fiber, Trowell (49) proposed that dietary fiber include those constituents of food resistant to hydrolysis by man s alimentary enzymes. Spiller (50, 51) suggested that confusion surrounding the term "fiber" be avoided by using the term "plantix" to denote those plant materials of polymeric nature not attacked by human digestive enzymes. 

Interest in dietary components which explain differences in breast cancer rates comes from strong correlations between nutrient supply within nations and their age-adjusted rates for breast cancer (11). The most frequently cited dietary components related to higher risk of breast cancer are total fat, total protein, calories, animal fat, animal protein, and a lack of fiber. Overall it has not been possible to identify the specific dietary constituents responsible for the observed incidence since the intakes of many dietary factors such as protein, fat, and calories are strongly intercorrelated. Other studies of nutrient intake and breast... 

The influence of garlic on the cancer process cannot be considered in isolation since several dietary components can markedly influence its overall impact. Among the factors recognized to influence the response to garlic are total fat, selenium, methionine, and vitamin A [30, 31, 134]. Amagase et al. [30] and Ip et al. [135] reported that selenium supplied either as a component of the diet or as a constituent of a garlic supplement enhanced protection against 7,12-dimethylbenz(a)anthracene (DMB A)-induced... 

Monoterpenes are known as constituents of the floral scents, essential oils, and defensive resins of aromatic plants [83]. Many monoterpenes are mommutritive dietary components found in the essential oils of cherry, mint, citms fruits, and herbs. The formation of various monoterpenes from GPP is catalyzed by different terpene cyclases [84]. 

A wide variety of animal species are subjected to the administration of drugs during their lifetime.The various animal species can encounter drugs and other dietary additives by different routes and this is dependent on the environment in which they are kept. Intensively reared animals tend to have considerable consistency in the components of their diets and thus are much less likely to encounter the range of naturally produced compounds that extensively produced animals encounter. The desire for less expensive dietary constituents and increased efficiency of use has induced feed manufacturers and producers to add enzyme supplements to diets of most farmed animals to reduce the negative effects of indigestible dietary carbohydrates, refactory proteins and unavailable minerals such as phosphorus. This use of dietary additives to improve nutrient utilization and environmental consequences of feeding animals intensively has been the subject of intense research activity in the last five years. " The... 

Matrix Components The term matrix component refers to the constituents in the material aside from those being determined, which are denoted as analyte. Clearly, what is a matrix component to one analyst may be an analyte to another. Thus, in one hand for the case of analyses for elemental content, components such as dietary fibre, ash, protein, fat, and carbohydrate are classified as matrix components and are used to define the nature of the material. On the other hand, reference values are required to monitor the quality of determinations of these nutritionally significant matrix components. Hence, there is a challenging immediate need for certified values for dietary fibre, ash, protein, fat, and carbohydrate. Concomitantly, these values must be accompanied by scientifically sound definitions (e.g. total soluble dietary fibre, total sulpha-ted ash, total unsaturated fat, polyunsaturated fat, individual lipids, simple sugars, and complex carbohydrates). 

The prophecy on semiochemical systematics in the headline quotation at the start of this chapter remains just that — an intriguing speculation. Some single-component chemosignals do turn up as apparently the main active compound in a complex secretion. In male gerbils (Meriones) one volatile, phenylacetic acid, appears to represent the dominant male state (Thiesen, 1974). Individuality must be added by further components — dietary or variable sebum constituents in this case. Indeed, amongst mammals and some reptiles, complex mixtures seem to be the norm very few taxonomically relevant examples have emerged. 

Botanical raw materials and their extracts therefore usually contain complex mixtures of several chemical constituents. For a large majority of botanical plant material and extracts of these used as dietary supplements, it is not known with certainty which of the various components is responsible for the purported pharmacological effect. It is generally believed that several constituents act synergistically to provide the purported effect. In actual practice, two or more of the chemical constituents present in the plant material are identified as marker compounds that are characteristic of the plant material to be tested, for identification and monitoring of the stability of the extracts. 

One issue not resolved by the DSHEA, specifically for botanical or herbal dietary products, is the lack of standardization of the active component. As mentioned previously, the standardization of Echinacea products is based on the level of plant material rather than one specific compound. In many cases, the specific compound responsible for the health benefit has not been fully characterized. In addition, many phytochemical constituents may participate in an observed health benefit. The lack of standardized preparations may, in fact, be responsible for the conflicting reports surrounding the biological activity of Echinacea. 

Cellulose. Fiber components differ in their ability to bind to bile (41), the primary route of excretion of manganese (9). Cellulose, the most abundant natural fiber, has been studied for its potential effects on bile and lipid metabolism (42). It is naturally present in high fiber diets and is also commonly added to many commercially-produced food products. Previous studies have shown cellulose to decrease intestinal uptake of a variety of minerals, including zinc, phosphorus, calcium, magnesium, and iron (32,43,44). In many cases, however, the effect of cellulose has not been considered to be anti-nutritional (32). It has been generally believed that cellulose has a lower binding affinity for minerals than other constituents of dietary fiber (33,45). 

Insects use camouflage coloration as a means of avoiding predation. The green color of the tobacco hornworm larvae, (Manduca sexta) can be separated into constituent blue and yellow components. The water soluble blue component is the biliprotein, insecticyanin. The yellow color is derived from lipoprotein bound carotenes. This lipoprotein, lipophorin, is the major lipid transport vehicle in insect hemolymph. In addition to transporting dietary lipid, lipophorin is also involved in the transport of lipophilic insecticides. Nearly all the recovered radioactivity in hemolymph from topically applied [14c] ddt is associated with lipophorin. Lipophorin of adult M. sexta is larger, less dense and is associated with small amounts of a third, adult specific, apoprotein. Alterations in adult lipophorin density, lipid content and apoprotein stoichiometry can be caused by injection of the decapeptide, adipokinetic hormone. 

If we expand our notions of environmental chemicals to include natural components of the diet, we might then begin to see why it is of great importance to continue to study their health effects. Diet, as we have seen in Chapter 7, importantly contributes to human cancer rates. We do not understand a great deal about why this is, but it is surely far more complex than the rate and form of our fat and fiber intakes. Perhaps industrial products are not the major human carcinogens, but natural products may well be. To make matters more complicated, it is also apparent that many natural dietary constituents protect against certain cancers. Indeed, some may increase the risks of certain cancers and reduce that of others It is not unexpected that some industrial chemicals will be shown to have these same properties. 

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