BACKGROUND: Dietary intervention studies incorporating phytosterol-enriched margarine spreads have reported significant decreases in total and low-density lipoprotein (LDL) cholesterol in populations with both normal lipid levels and those with hypercholesterolemia. There is emerging support for more diverse and lower-fat phytosterol-enriched matrixes. Controversy exists, however, over whether phytosterol-enriched foods affect serum fat-soluble vitamins. OBJECTIVE: We investigated whether a flavanol-rich cocoa snack food containing phytosterols would decrease total and LDL cholesterol levels in subjects with hypercholesterolemia and significantly affect serum fat-soluble vitamins and carotenoids. DESIGN: A randomized, double-blind parallel arm study design was used. Subjects were randomized to one of two dietary treatments: a cocoa flavanol-enriched snack bar containing 1.5 g phytosterol (n=32), or a control product containing no phytosterols (n=35). Subjects consumed two servings per day. RESULTS: Consumption of the phytosterol-enriched snack bars but not control bars for 6 weeks was associated with significant reductions in plasma total (4.7%; P<0.01) and LDL cholesterol (6%; P<0.01), and the ratio of total to high-density lipoprotein cholesterol (7.4%; P<0.001). There were no changes in high-density lipoprotein cholesterol, triglycerides, or lipid-adjusted lycopene, beta-cryptoxanthin, lutein/zeaxanthin, alpha-carotene levels, or levels of serum vitamins A or E. A significant reduction in lipid-adjusted serum beta-carotene was observed in the phytosterol but not the no-phytosterol-added group (P<0.05). CONCLUSIONS: This study supports the use of a novel phytosterol-enriched snack bar to effectively reduce plasma total and LDL cholesterol levels in a population with hypercholesterolemia. The data suggest that the incorporation of this snack food into a balanced diet represents a practical dietary strategy in the management of serum cholesterol levels.