To confirm the safety and efficacy of a low-calorie mayonnaise supplemented with phytosterol esters (PEM) at a daily consumption dose of 884 mg given for 12 weeks with the goal of lowering serum low-density lipoprotein (LDL) cholesterol levels, we conducted a double-blind comparative study in healthy adults with marginally high serum levels of LDL cholesterol and total cholesterol using a mayonnaise without phytosterol esters supplementation (CM) as the control food. Serum LDL cholesterol levels decreased significantly in the PEM group as compared with the CM group during the 12-week intervention period (136.3 ± 16.4 vs. 145.0 ± 19.3 mg/dL at Week 8 (P < 0.05) and 135.0 ± 17.4 mg/dL vs. 144.9 ± 17.5 mg/dL at Week 12; P < 0.05). No observable adverse effects were observed due to the ingestion of PEM in this study. The safety of PEM was again confirmed by an additional clinical study in which healthy adult subjects ingested a 3-fold greater amount of PEM (2,652 mg of phytosterol esters as a daily dose) for 4 weeks. Thus, we concluded that PEM is effective in lowing serum levels of LDL cholesterol and is safe and well tolerated without any clinical problems.