Consumption of soy products is speculated to reduce the risk and progression of some disease conditions. The underlying mechanisms mediating this effect are uncertain, but the lowering of oxidative stress has been suggested. This study was aimed at investigating the effect of soymilk on antioxidant status and lipid peroxidation in apparently healthy individuals. Five hundred milliliters of soymilk was taken daily by each of 39 apparently healthy individuals for a period of 28 days. Two sets of blood samples (baseline and after 28 days of soymilk intake) were collected and assayed for total antioxidant capacity (TAC), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione S-transferase (GST), manganese (Mn) and zinc (Zn) levels, using standard methods. Consumption of soymilk significantly increased serum TAC and reduced serum MDA when compared with baseline values (P < .001, P < .001 respectively). The decrease in MDA concentration was significantly contributed by the women (P < .001). Mean serum Mn was also significantly reduced (P = .03) when compared with baseline values. There were no changes in serum Zn concentration and the activity of SOD enzyme. The serum GST activity was significantly increased in men (P = .02) and significantly reduced in women (P < .001) in comparison with their corresponding baseline values. Daily consumption of soymilk enhanced antioxidant status and this led to reduced lipid peroxidation. It also resulted in a significant reduction of Mn. The dietary use of soymilk as an adjuvant to supplement meals seems beneficial health wise. However, soymilk should be taken with caution as it could result in micronutrient deficiency.
Keywords: lipid peroxidation; manganese; soymilk; total antioxidant status; zinc.