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Effects of zinc supplementation on erythrocyte and lymphocyte antioxidant status of the Italian subjects

Zinc (Zn) is essential for a great number of biochemical activities and biological functions. Long-term marginal intakes of Zn and a decreased absorptive efficiency could severely compromise Zn status in older individuals. Zinc plays an important role in the antioxidant defence and Zn deficiency has been associated with increased reactive oxygen-induced damage in various tissues and with alteration in antioxidant enzymes. The aim of this work was to explore the effect of long-term supplementation with two moderate dose of Zn (15mg/day or 30mg/day) on oxidative stress parameters and on cellular stress and oxidative markers in 108 healthy elderly (70-85yrs) recruited in Rome. Plasma carotenoids and lymphocytes a-tocopherol, B-carotene and coenzyme Q10 (coQ10) were determined by high-performance liquid chromatography. Lymphocytes were isolated from whole blood using ficoll gradient. Nitric Oxide (NO) assay were performed spectrophotometrically.

The measurement of the absorbance due this azo-chromophore accurately determines NO2- concentration. For the determination of SOD, GPx and catalase (CAT) activity in lymphocytes and to test the erythrocytes levels of GSH/RSH and MDA were used spectrophotometric kits provided by Oxis (Oxis International, inc. Portland, USA). The percentage of haemolysis in erythrocytes was determined spettrophotometrically at 540nm. The methemoglobin (Methb), an oxidant product pf haemoglobin, was tested using a Kit by Pokler Italia. The dietary intakes of micronutrients (carotenoids, retinol, vitamin E) and minerals (Zn, copper and iron) were statistically similar before and after Zn supplementation for both sexes and no significant changes in fruits and vegetables consumption were noted during the entire period of study. Zn supplementation, after the 6-mo period, had no significant effects on all the measured parameters either in both genders considered separately or in a gender combined analysis.

All the results were in a range of normality. The results of this study provide further information regarding the age-related oxidative stress in free-living healthy elderly in Rome, and on the effects of nutritional Zn supplementation on the red-ox status. Our data showed that long-term supplementation with two moderate doses of Zn had no significant effects on the markers of oxidative stress measured. In conclusion, it appears that, differently from unhealthy populations, this kind of supplementation is an inefficient way to increase antioxidant defence in a healthy population.

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