Plant foods vegetables

While most people consume animal products if they have the opportunity, it is possible to live solely on plant foods. Vegetable diets, however, tend to be poorly digested and to cause distention of the gut by gas and residues. They increase the frequency of defecation and micturition and are likely to be low in protein, fat and calcium and devoid of vitamin B12. 

Cellulose is the main constituent of plant cell walls, where it usually occurs together with hemi-celluloses, pectin and lignin. Since cellulase enzymes are absent in the human digestive tract, cellulose, together with some other inert polysaccharides, constitute the indigestible carbohydrate of plant food (vegetables, fruits or cereals), referred to as dietary fiber. Cellulases are also absent in the digestive tract of animals, but herbivorous an-... 

The general recommendations on energy and fat intake are similar to those for the avoidance of heart disease. However, the recommendation to consume a variety of fruits and vegetables is based partly on the putative presence of diverse protective factors in plant foods. This concept does provide, at least in principle, a rationale for the functional health benefits of plant foods beyond the simple provision of nutrients at a level that prevents symptoms of deficiency. 

The discovery that, in industrialised societies, diets deficient in fruits and vegetables can effectively double the risk of developing many different types of cancer has focused renewed attention on the beneficial properties of these foods (Block e/a/., 1992 Patterson ef a/., 1990 Southon and Faulks, 2002). As we have seen, plant foods are rich in micronutrients, but they also contain an immense variety of biologically active secondary metabolites providing colour, flavour and natural toxicity to pests and sometimes humans (Johnson et ah, 1994). The chemistry and classification of such substances is still a matter for much research and debate, but this has not prevented attempts to isolate and exploit substances that have variously been termed protective factors , phytoprotectants , phytochemicals and nutraceuticals . Phytochemical compounds include ... 

The antioxidant activities of carotenoids and other phytochemicals in the human body can be measured, or at least estimated, by a variety of techniques, in vitro, in vivo or ex vivo (Krinsky, 2001). Many studies describe the use of ex vivo methods to measure the oxidisability of low-density lipoprotein (LDL) particles after dietary intervention with carotene-rich foods. However, the difficulty with this approach is that complex plant foods usually also contain other carotenoids, ascorbate, flavonoids, and other compounds that have antioxidant activity, and it is difficult to attribute the results to any particular class of compounds. One study, in which subjects were given additional fruits and vegetables, demonstrated an increase in the resistance of LDL to oxidation (Hininger et al., 1997), but two other showed no effect (Chopra et al, 1996 van het Hof et al., 1999). These differing outcomes may have been due to systematic differences in the experimental protocols or in the populations studied (Krinsky, 2001), but the results do indicate the complexity of the problem, and the hazards of generalising too readily about the putative benefits of dietary antioxidants. 

Epidemiological data on the protective effects of plant foods provides convincing evidence that a high consumption of brassica vegetables is inversely... 

Singh, G., Kawatra, A., and Sehgal, S., Nutritional composition of selected green leafy vegetables, herbs and carrots. Plant Foods Human Nutr., 56, 359, 2001. 

Gomez, M.I., Carotene content of some green leafy vegetables of Kenya and effects of dehydration and storage on carotene retention, J. Plant Foods, 3, 231, 1981. 

Khanum F, Swamy MS, Sudarshana Krishna KR, Santhanam K and Viswanathan KR. 2000. Dietary fiber content of commonly fresh and cooked vegetables consumed in India. Plant Foods Hum Nutr 55 207-218. 

S.O. Mueller, M. Schmitt, W. Decant, FI. Stopper, J. Schlatter, P. Schleier and W.K. Lutz, Occurrence of emodin, chrysophanol and physcion in vegetables, herbs and liquors. Genotoxicity and anti-genotoxicity of the anthraquinones and of the whole plants. Food Chem. Toxicol. 37 (1999) 481 -91. 

Vegetable waste has a very high moisture content Liquid will tend to accumulate in plastic worm bins, and the worms may drown unless adequate drainage is provided. If there is a reservoir at the bottom of the bin, the liquid can be drained off through a spigot This liquid contains some plant foods, which can be recycled by watering it onto the compost pile. 

Potato is in the lower range of folate contents among plant foods (Table 14.1) as are other underground organs, ranking ahead of polished rice but behind green leafy vegetables and pulses. A number of factors may affect the bioavailability of folates from plant foods. These... 

Nickel occurs mainly in plant foods, especially grains and vegetables with little in animal food sources or fats. 

Flavonols are present in plant foods mainly in the leaves and in the outer parts of plants with quercetin and kaempferol the most common ones. Quercetin and its glycoside are ubiquitous in fruits and vegetables. Conversely, kaempferol and myricetin are less distributed (Table 7) [21-23]. 

Fermentation of plant foods generally increases mineral bioavailability. Studies by Ranhotra and coworkers (121, 122 for example) have shown increased available zinc from breads and cookies that have undergone yeast fermentation. Also, iron was shown by these workers to be more highly available from unfortified breads than from breads fortified with wheat bran, soy flour or other whole grain vegetable flours. 

Presents a table (Table 7) of chloropyll, carotenoid, and vitamin E levels (in pg/g dw) of green leaf tissue, vegetables, green and red fruits (tomato, red pepper), and nongreen plant foods (carrots, cauliflower). 

Sultana B, Anwar F (2008). Flavonols (kaempeferol, quercetin, myricetin) contents of selected fruits, vegetables and medicinal plants. Food Chemi, 108 879-884. 

Discrimination among all of these is a trivial exercise. Both B vitamins and C were easily quantitated in prepared mixtures as expected [59], but it was also relatively easy to measure each one after its simple extraction into aqueous buffer from pharmaceutical preparations, as well as (in the case of vitamin C) from extracts of fruit, fruit juices, and vegetables. A very thorough inventory of tests for possible interferences was run and the resultant analytical data for the vitamins compared extremely well with the labelled contents on the packages of pharmaceutical products and with the data in compendia that list the average compositions of vitamins and other essential products in plant food materials [33]. Analysis of the major fat soluble D2 and D3 vitamins (ergocalciferol and cholecalciferol) has not progressed with the... 

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