Studies on the bioavailability of micronutrients from Indian foods

Hemalatha, S (2006) Studies on the bioavailability of micronutrients from Indian foods. PhD thesis, University of Mysore.

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Abstract

Cereals and legumes are staple foods in the diet of many populations, especially in developing countries, where they are the main source of energy and protein. These are also the main sources of minerals such as iron and zinc. Even though these food grains can substantially contribute to an adequate mineral intake, the mineral availability, especially as far as iron is concerned is generally poor, since it is affected mainly by phytic acid, tannin and dietary fibre components inherent in them. While the effects of these constituents on iron absorption have been the subject for numerous studies, little is known about the influence of the same on zinc availability. Even if net zinc intake from these staples appears adequate, compromised zinc status in populations dependent on these grains is common. It is therefore important to identify and evaluate dietary factors that interfere with zinc absorption. With such knowledge, strategies of avoiding or limiting components with inhibitory effects on zinc absorption and of choosing food or dietary components that enhance the same may be adopted. As such, a number of staple cereals and pulses commonly consumed in India have been examined in this investigation for zinc bioaccessibility value. These staple grains are generally consumed in the cooked form, and such a treatment may have a marked effect on the matrix and composition of food and therefore on iron and zinc availability. Hence, the bioaccessibility values of these two minerals have also been examined in heat- processed food grains. Iron deficiency is often accompanied by other nutrient deficiencies such as zinc and copper deficiencies, especially when iron deficiency is caused by insufficient dietary intakes of micronutrients, as is often the case in developing countries. As a result, supplements containing iron and multiple trace elements and minerals are used by millions of people world-wide. It is important to provide detailed information regarding safe upper intake limits for supplements to minimize adverse effects on mineral absorption caused by mineral - mineral interactions. Iron supplements have been reported to decrease zinc absorption in pregnant women and lower serum zinc concentrations. Furthermore, a negative effect of iron provision through food fortification on zinc absorption could further exacerbate the zinc deficiency status commonly prevalent in populations dependent on plant foods. It is therefore important Chapter I 37 to practically evaluate any possible interactions between iron & zinc. Calcium has been shown to interfere with the absorption of non-heme and heme iron in a dose-dependent manner. The addition of milk or milk products to common meals brings the absorption of iron by as much as 50 - 60%. Effect of calcium on zinc availability at nutritional concentrations is reported to be less pronounced in human studies. However, a negative interaction of calcium with zinc absorption is possible when the former is consumed at supplementary levels. In this context the influence, if any, of exogenous iron and calcium on zinc bioaccessibility from selected food grains has also been assessed. Domestic food processing such as germination and fermentation is known to affect the bioavailability of iron and zinc, probably by modulating the factors that act as promoters or inhibitors of mineral absorption. In this context, the much- practiced germination and fermentation of grains as encountered in Indian dietary have been examined for their influence on zinc and iron bioaccessibility. Various organic acids that are present in foods, such as ascorbic, citric, malic & lactic acid have been shown to facilitate the absorption of iron. Use of food acidulants such as amchur, lime, tamarind and kokum is common in Indian dietary. The presence of organic acids supplied by these food acidulants may have an influence on zinc bioaccessibility from the food grains. Thus, the influence of these acidulants on zinc bioaccessibility from representative food grains has also been assessed in this investigation. An in vitro procedure involving equilibrium dialysis during simulated gastrointestinal digestion was adopted throughout this investigation in all the above zinc and iron bioavailability determination studies. This method essentially measures the fraction of the total mineral in the food or diet that is available for uptake by the intestinal brush border cell membranes, in other words, the ‘bioaccessibility’ of the mineral. In view of the recent redefining of the terms related to bioavailability, we prefer to use the term ‘bioaccessibility’ when referring to the results obtained with this in vitro procedure.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	Cereals and Pulses-; Bioavailability of Zinc and Iron; Influence of- food acidulants; Exogenous Iron, Calcium, Protein and Common salt; Germination
Subjects:	600 Technology > 08 Food technology > 21 Cereals 600 Technology > 08 Food technology > 16 Nutritive value 600 Technology > 08 Food technology > 22 Legumes-Pulses
Divisions:	Dept. of Biochemistry
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	12 Mar 2010 10:19
Last Modified:	18 Nov 2016 11:18
URI:	http://ir.cftri.res.in/id/eprint/9382

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