Assessment of zinc deficiency and effect of dietary carrot, amchur and onion on zinc status during repletion in zinc-deficient rats.

BACKGROUND: Food acidulants, ß-carotene-rich vegetables and sulfur compound-rich Allium spices are known to improve zinc bioaccessibility from food grains. This animal study evaluated the positive influence of these promoters of zinc bioaccessibility on zinc status during zinc repletion in Wistar rats previously rendered zinc-deficient by feeding a zinc-deficient semi-synthetic diet for 4 weeks. Groups of these zinc-deficient animals were subsequently maintained on a zinc-containing grain-based diet for 2 weeks. Various experimental diets consisted of the grain-based diet supplemented with (1) carrot, (2) onion, (3) amchur, (4) carrot + amchur and (5) onion + amchur. RESULTS: Zinc deficiency was confirmed by lower zinc concentration in tissues and bones and lower activity of zinc-containing enzymes. Zinc concentration was 10-15% lower in serum, liver and kidney of zinc-deficient rats. Bone weight in zinc-deficient rats was 20% lower than that in normal rats. Activities of zinc-containing enzymes (hepatic superoxide dismutase and alcohol dehydrogenase and serum alkaline phosphatase) were lower in the zinc-deficient group. Animals fed diets supplemented with these promoters of zinc bioaccessibility showed better zinc status in tissues and bones compared with those repleted with the control stock diet. CONCLUSION: This animal study supports the claim of promoters of zinc bioaccessibility for improving zinc status, which may find practical application.

Promoting influence of combinations of amchur, ß-carotene-rich vegetables and Allium spices on the bioaccessibility of zinc and iron from food grains.

Deficiencies of iron and zinc among the population dependent on plant foods necessitate strategies to maximize their bioavailability. In this context, specific combinations of promoters of iron and zinc bioaccessibility-namely, amchur (0.75 g/10 g), ß-carotene-rich vegetables (2.5 g/10 g) and Allium spices (1.5 g/10 g)-were evaluated for a possible additive/synergistic effect on the bioaccessibility of iron and zinc from food grains. The positive influence on the bioaccessibility of iron was additive in the case of combinations of amchur-carrot, amchur-garlic, onion-carrot, and onion-amaranth in a few specific grains. Positive influence on the bioaccessibility of iron was even synergistic for combinations of amchur-onion and amchur-garlic in a few grains. The influence of amchur-garlic and amchur-onion was additive while the combination of amchur-amaranth and amchur-garlic produced a synergistic-promoting influence on zinc bioaccessibility in a few instances. This observation would be useful in evolving dietary strategies to maximize the bioavailability of minerals from grains.

Influence of combinations of promoter and inhibitor on the bioaccessibility of iron and zinc from food grains.

Inherent phytic acid and tannins interfere with bioavailability of iron and zinc from plant-based foods. Food acidulants, ß-carotene-rich vegetables and Allium spices are understood to promote mineral bioaccessibility (an estimate of bioavailability using in vitro method) from food grains. In this study, we have verified whether these promoters would counter negative effects of phytate and tannin on bioaccessibility of iron and zinc from grains. Combinations of promoters - amchur, carrot and onion with phytic acid and tannin exogenously added individually were examined for their influence on iron and zinc bioaccessibility from the food grain. Effect of these promoters was generally dominant in the presence of phytic acid or tannic acid. The negative effect of the inhibitor was not only annulled, but also the positive influence of the promoter was fully retained. This information helps to evolve diet-based strategy to maximize mineral bioavailability and prevent deficiency situations prevalent in population dependent on plant foods.

Higher bioaccessibility of iron and zinc from food grains in the presence of garlic and onion.

Bioavailability of micronutrients iron and zinc is particularly low from plant foods. Hence there is a need to evolve a food-based strategy to improve the same to combat widespread deficiencies of these minerals in a population dependent on plant foods. Dietary sulfur-containing amino acids have been reported to improve the mineral status of experimental animals. Our objective was to examine whether sulfur compound-rich Allium spices have a similar potential of beneficially modulating the mineral bioavailability. In this context, we examined the influence of exogenously added garlic and onion on the bioaccessibility of iron and zinc from food grains. Two representative cereals and pulses each were studied in both raw and cooked condition employing two levels of garlic (0.25 and 0.5 g/10 g of grain) and onion (1.5 and 3 g/10 g of grain). The enhancing effect of these two spices on iron bioaccessibility was generally evidenced in the case of both the cereals (9.4-65.9% increase) and pulses (9.9-73.3% increase) in both raw and cooked conditions. The two spices similarly enhanced the bioaccessibility of zinc from the food grains, the extent of increase in cereals ranging from 10.4% to 159.4% and in pulses from 9.8% to 49.8%. Thus, both garlic and onion were evidenced here to have a promoting influence on the bioaccessibility of iron and zinc from food grains. This novel information has the potential application in evolving a food-based strategy to improve the bioavailability of trace minerals and hence contributes to the human health benefit.

Influence of exogenous iron, calcium, protein and common salt on the bioaccessibility of zinc from cereals and legumes.

We have earlier reported the zinc bioaccessibility from cereals and pulses and documented the influence of heat processing, germination and fermentation on the same. In the present study, we have assessed the influence of exogenous iron and calcium equivalent to their supplemental levels on the bioaccessibility of zinc from food grains that generally are the major components of meal in India. Bioaccessibility measurement was made by a procedure involving equilibrium dialysis during simulated gastrointestinal digestion. Exogenous iron equivalent to therapeutic levels (5mg per 10g of cereal-legume combination) significantly reduced the bioaccessibility of zinc from the food grains tested, the percent reduction being 32.4. Exogenous calcium equivalent to therapeutic levels (83mg per 10g of the cereal-legume combination) also significantly reduced (by 27.4%) the bioaccessibility of zinc from the tested food grains. The negative influence of exogenous iron and calcium was similar in both raw and cooked grains. Such negative influences on the bioaccessibility of zinc were however not seen when exogenous iron and calcium were only moderate (up to four times the intrinsic level). A study of the influence of exogenous protein on the bioaccessibility of zinc from food grains revealed that soy protein isolate added at amounts to result in a total protein content of 20% produced contrasting effects on zinc and iron bioaccessibility from cereals - rice and sorghum. While soy protein had a negative effect on iron bioaccessibility from these food grains, the same produced an enhancing effect on zinc bioaccessibility (an increase of 50% and 90% increase) from raw and cooked grain, respectively). Exogenous sodium chloride (at 5% level) potentiated the positive effect of soy protein on zinc bioaccessibility, and effectively countered its negative effect on iron bioaccessibility. The observed negative influence of supplemental iron and calcium on zinc bioaccessibility suggests that zinc supplementation may be necessary in the Indian context, whenever iron and calcium supplements are taken, to compensate for the reduction in zinc bioaccessibility.