Anti-nutrients

By necessity, herbivores have evolved GIT and systemic compensatory mechanisms that allow them to subsist on plant-based diets that have limited nutrient quality and include phytochemicals. Still, herbivores remain susceptible to some of the anti-nutrient and toxic phytochemicals. For example, several herbivores are sensitive to the phytotoxins associated with autumn crocus, which include colchicine (Yamada et al, 2000). As a consequence, herbivores tend to select species and portions of plants based on a combination of nutrient quality and concentrations of phytochemicals (Yeager et al, 1997), and this has an impact on habitat selection and plant ecology (Duncan and Gordon, 1999). Carnivorous species have not been under selective pressure to develop similar compensatory mechanisms, generally have only limited abilities to subsist on plant-based diets, and in many cases are less tolerant of phytochemicals. 

Second, the presence of anti-nutrients requires heightened stimulation of digestive secretions (Santoro et ah, 1997). This increases the costs of digestion, which are already appreciable (Tamminga et al, 1995). 

The complex polymers in feedstuffs are broken down to the constituent building blocks by a sequential process. Hydrolysis of the polymers is initiated in the lumen of the GIT by enzymes and other secretions produced by the pancreas, stomach, intestine, liver and gall bladder, and other GIT tissues, and completed by another suite of enzymes associated with the brush border membrane (BBM) or intracellular organelles. Anti-nutrient phytochemicals can decrease the hydrolysis of feedstuffs, and thereby reduce nutrient availability, either by increasing the inherent resistance of the polymers to hydrolysis or by decreasing the activities or amounts of enzymes and other secretions produced by the GIT. 

Some of the best investigated anti-nutrients are the enzyme inhibitors present in legumes and other plants. The Bowman-Birk and the Kunitz inhibitors of trypsin and other proteases are among the best characterized. In contrast to the non-specific and widespread influences of tannins and lectins (Carmona, 1996), the Bowman-Birk, Kunitz and other such inhibitors target specific enzymes. Corresponding with this, proteases and other digestive enzymes vary in sensitivity to the different inhibitors. 

Phytate (myo-inositol hexaphosphate Fig. 15.3, structure 33) is found in many food species and can be considered as a phytochemical. Its role in the plant is primarily as a phosphate store in seeds, but it is found in other tissues as well, for example, tubers (Harland et al., 2004). Phytate and its hydrolysis products are anti-nutrients that chelate metal ions and thus reduce their bioavailability (Persson et al., 1998 House, 1999). This is particularly a problem with cereal grains, but pre-processing can improve mineral absorption from these foods (Agte and Joshi, 1997). There is some concern that high phytate foods could also contain higher levels of toxic heavy metals caused by natural accumulation. Plants also contain phytate-degrading enzymes that can also influence metal ion bioavailability (Viveros et al., 2000). 

Biological effects of plant proteins on human health have attracted wide attention in the recent past because of the presence of various anti nutrients such as trypsin inhibitors, hemagglutinins, and toxic principles U). Adequate cooking and/or processing inactivates these materials and can improve the quality... 

Ouality Factors Plant Breeding, Composition, Processing, and Anti-Nutrients." Friedman,... 

These investigations show the potential value of full fat winged bean as a broiler feed. However, further studies that define conditions for destruction of anti-nutrients which cause reduced growth performance should be performed. 

Tubers Tubers are quite commonly consumed by villagers in Burma. Other tropical countries also report sporadic use of winged bean tubers (59). However, in comparison to the available data on the nutrient, anti-nutrient composition and the protein quality of the seed flour, published data on the nutritional value of winged bean tuber is somewhat limited. The few reported studies dealing with a larger number of varieties grown in different locations (25,67-71) show that tubers are mainly composed of protein and carbohydrates. 

OECD (Organisation for Economic Co-operation and Development). (2002). Consensus document on compositional considerations for new varieties of potatoes key food and feed nutrients, anti-nutrients and toxicants. Series on the Safety of Novel Foods and Feeds, No. 4. ENV/JM/MONO(2002)5,26 pp. 

Antony, U. and Chandra, T. S. (1998). Anti nutrient reduction and enhancement in protein, starch and mineral availability in fermented flour of finger millet (Eleucine coracana).. Agric. Food Chem. 46, 2578-2582. 

Organisation for Economic Co-operation and Development (2004), Consensus Document on Compositional Considerations for New Varieties of Cotton (Gossypium hirsutum and Gossypium barbadense) Key Food and Feed Nutrients and Anti-nutrients, Series on the... 

CTs can be effective anti-nutrients against insects, especially at high concentrations as can be found in P. tremuloides (up to 18 % DW). ° Tannin effectiveness and mechanism of action has been debated, but it clearly depends both on variations in chemical structure and plant source, as well as on the biochemical conditions in the gut of the particular insect species. In P. tremuloides, CT levels were shown to be negatively correlated with gypsy moth and forest tent caterpillar larvae performance, although the effects were smaller than with the phenolic glycosides (C. P. Constabel and J. Spence, unpublished data). ... 

Food quality and food process control Anti-nutrient and toxic components Amygdalin (bitter almond) Buffer -glucosidase Potentiometric [15]... 

The analytes for each crop (listed as Parameters in Table 1) include maca o- and micronutrients. Proximates, (total) amino acids, fatty acids and a range of minerals are routinely analysed for every crop while analysis of vitamins and other minor components (toxins, anti-nutrients) is based on their known presence and importance in the particular crop. The OECD recommendations should be regarded as providing a basic set of components that may need to be augmented depending upon the details of the modification. In practice all those pubhca-tions listed in Table 1, where work was also carried out as part of a regulatory approval application, adhered closely to the OECD lists of recommended components. 

Shepherd LVT, McNicol JW, Razzo R, Taylor MA, Davies HV, McNicol JW. (2006) Assessing the potential for unintended effects in genetically modified potatoes perturbed in metabolic and developmental processes. Targeted analysis ofkey nutrients and anti-nutrients. Transgenic Res 15 409 25... 

The nutrients, anti-nutrients, and secondary metabolites listed in Table 1 were assessed as part of the composition evaluation of maize event NK603 (11). A total of 105 comparisons between NK603 and its non-transgenic control were conducted for U.S. sites in 1998 and the E. U. sites in 1999. The values for the biochemical components for com event NK603 were similar to the control or were within the published range observed for non-transgenic commercial com hybrids. 

Similarly to the biosafety programme, the main outcome of the foods and feeds programme is the set of Consensus Documents on compositional considerations of new varieties of specific crops. The Task Force documents compile a common base of scientific information on the major components of crop plants, such as key nutrients, toxicants, anti-nutrients and allergens. These documents constitute practical tools for regulators and risk/safety assessors dealing with these new varieties, with respect to foods and feeds. To date, 20 Consensus Documents have been published on major crops and on general considerations for facilitating harmonisation. They constitute the Series on the Safety of Novel Foods and Feeds which is also available on the OECD s website at no cost (www.oecd.org/biotrack). 

In the area of food and feed safety (dealt with by the Task Force), consensus documents are focused on the nutrients, anti-nutrients or toxicants, the use as a food/feed and other relevant information on particular products. Reference is made to the concept of substantial equivalence, as it is considered that a comparative approach focusing on the determination of similarities and differences between the genetically engineered food and its conventional counterpart aids in the identification of potential safety and nutritional assessment. 

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