Effects of fresh and heated soy oil on nitrite level in adult male rats. Shown are the nitric level changes in rats fed with basal diet (control), fresh soy oil (FSO), soy oil heated once (1HSO), soy oil heated twice (2HSO), soy oil heated five times (5HSO) or soy oil heated ten times (10HSO). The results are expressed as percentage based on baseline values. Data shown as means ± S.E.M. (n = 7), p < 0.05 indicates significant difference compared to acontrol, bFSO group.