Serum and liver lipids in rats fed diets containing corn oil, cottonseed oil, or a mixture of corn and cottonseed oils

Previous research has demonstrated that the total replacement of corn oil ( CO) with cottonseed oil (CSO) in the diets of growing male rats results in a lowering of the total cholesterol (TC) concentration in the serum. It is not, however, known if a partial replacement of dietary CO with CSO would b e sufficient to lower TC levels, nor is the effect of replacing dietary CO with CSO on other indices of cholesterol status (e.g., the levels of high-d ensity lipoprotein cholesterol [HDL-C], non-HDL-C [i.e., very-low and low-d ensity lipoprotein-cholesterol], or the TC/HDL-C ratio). Growing male rats were fed diets having CO, CSO, or a CO/CSO (1:1, w/w) oil mixture (OM) as t he source of dietary oil (diet groups CO, CSO, and OM, respectively). There were no differences between CO and OM groups for TC, HDL-C, non-HDL-C, or the TC/HDL-C ratio. However, TC was significantly lower (p less than or equ al to 0.05) for the CSO group than the CO group (2.85 vs. 3.23 mmol/l, or 1 10 vs. 125 mg/dl, respectively) as was HDL-C (1.83 vs. 2.13 mmol/l, or 71 v s. 82 mg/dl, respectively), but there were no differences between these gro ups for non-HDL-C or the TC/HDL-C ratio. Diet had no effect on serum trigly cerides (TGs) or on total liver content of either cholesterol or TGs. Thus, partial (50%) replacement of CO with CSO was without effect on any of thes e serum indices of cholesterol status, but total replacement resulted in lo wer TC and HDL-C, without affecting non-HDL-C or the TC/HDL-C ratio. Becaus e, relative to CO, CSO has higher levels of saturated fatty acids but lower levels of monounsaturated and polyunsaturated fatty acids, the cholesterol -lowering effect of CSO appears to be unrelated to its fatty acid compositi on, and may be caused by a component of its nonsaponifiable fraction.