The present study was designed to assess the effects of regular and low-linolenic acid canola oil on the blood lipid parameters of 40 (20 men and 20 women) non-insulin-dependent diabetes mellitus subjects, to determine whether canola oil has nutritional benefits in the clinical treatment of NIDDM, with particular attention to any benefits of linolenic acid (LNA). The study also assessed the effects these oils on the oxidative susceptibility, fatty acid composition, and particle size of the LDL fraction. A total of 36, newly diagnosed, NIDDM subjects (16 men and 20 women) were randomly assigned to four experimental groups: regular canola oil (CAN); low-linolenic acid canola oil (LLNA); sunflower oil (SNFLR); and a control (CONT) group who continued their usual diet. Plasma total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), and triglyceride (TAG) concentrations were determined. There were no significant effects of diet on plasma TC, LDL-C, HDL-C,or TAG concentrations during any of the study intervals (0-56, 0-28, or 28-56 days, respectively). Similarly, there were no diet effects for LDL oxidation rate or the total amount of conjugated dienes produced over the entire experimental period (0-56 days). A significant diet effect was observed on the change in LDL oxidation rate during the study period 28-56 days. Diet x gender interactions were also observed for changes in the levels of the following LDL fatty acids. Significant gender differences occurred for all LDL particle size parameters over the 0-56 day study period. (Abstract shortened by UMI.)