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Effect of zinc supplementation on oxidative stress and antioxidant parameters in middle-aged and older European subjects

Oxidative stress has been reported to increase with aging in relation with an increased production of free radicals by the mitochondria and/or a decreased level of antioxidant defences. In aging, uncontrolled oxidative stress results in an increased risk of oxidative pathologies such as CVD, dementia and diabetes. Zinc (Zn), as biological antioxidant, could act in preventing increased oxidative stress in Elderly. This study is aiming to investigate the effects on health of a Zn supplementation in free-living subjects in late middle-aged (55-70yrs) and older aged (70-85yrs).

In the present work, we measured the effect of a Zn supplementation on oxidative stress parameters monitored by plasma SH groups, TBAR's and blood total glutathione. Zinc status was measured in plasma, urines and erythrocytes. Subjects received 15mg/d or 30mg/d Zn as gluconate or a placebo form for 6 months. Measurements were carried out at the entry (T0), and after 3 (T3) and 6 months (T6). At the entry, only 5.6% of the older subjects and 4.8% of middle aged exhibited a biological Zn deficiency (plasma Zn < 10.7µmol/L).

At baseline, when we compared oxidative status between men and women, significant differences were observed, TBAR's levels were higher and GSHt levels lower in women. But no antioxidant beneficial effects of Zn supplementation were observed after 3 or 6 months. In Zn deficient subjects, Zn status was restored but no significant antioxidant effect of Zn supplementation was observed. It seems that oxidative status was higher in women compared to men. Our data point out the limits of a single antioxidant supplementation in older to counteract oxidative stress. Other beneficial effects of Zn supplementation (immunity, cognitive functions, osteoporosis) can be expected but regarding oxidative stresses a single Zn supplementation failed to show beneficial effects.

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