Last update:
01-Dec-2010

OBJECTIVE Free radicals are produced in the human organism during normal metabolism, or as a result of the effect of certain food ingredients or pollutants. Free radicals can cause damage to lipids, proteins and DNA, by which they are thought to be involved in the pathogenesis of various diseases and in the process of aging. As blood antioxidant levels reflect the antioxidant capacity of the organism, many investigators have tried to correlate these levels with certain diseases. The effect of age on the total antioxidant capacity (TAC) of the human organism remains unclear, although molecules damaged by free radical activity, such as lipid peroxides, increase with age. If TAC is to be used for estimating the effect of certain diseases on antioxidant capacity, or as a prognosis/diagnosis indicator, the effect of age on the TAC values of normal individuals needs to be estimated for each specific method used. In the present study, TAC was measured via the inhibition of oxidation of 2,2΄-azino-bis(3-ethylbenthiazoline)-6-sulfonic acid (ABTS) by the ferryl myoglobin-H₂O₂ system in blood and urine samples of residents of Thessaloniki, and the values were correlated with age.

METHOD Serum samples of 118 residents of Thessaloniki were used. A questionnaire concerning age, sex, district of residence, type of occupation, dietary behavior and special habits such as smoking was completed, and regular smokers were excluded from the study. The samples were divided into four groups according to age: 5−17, 18−35, 36−60 and 61−90 years. In addition, total urine antioxidants were measured in 87 samples from participants in all age groups. Antioxidant activity was estimated using the Cayman antioxidant assay kit and expressed as trolox equivalents.

RESULTS No correlation was observed between TAC values and sex. An increased concentration of total serum antioxidants was found in the older age groups. An increase with age in total blood and urine antioxidant activity was observed up to 36−60 years, followed by a small decrease in blood levels and a small increase in urine levels in the 61−90 years group. The greatest increase (79% in serum, p=0.000, 83% in urine, p=0.000) was observed between the 18−35 years and the 36−60 years groups.

CONCLUSIONS The differences recorded in the literature concerning the effect of age on TAC may be explained by the differences in specificity and sensitivity of the methods used. Malnutrition, stress, passive smoking, reduced and unstable sleep, in combination with high levels of sex hormones may explain the lower TAC observed in the 18−35 years age group.

Key words: Age, Antioxidants, Oxidative stress, Serum, Urine.