BACKGROUND Psyllium and oat bran have been shown to lower plasma LDL cholesterol levels in different populations. Hypercholesterolemia is prevalent in the Northern part of Mexico and might be associated to dietary habits and sedentary lifestyle. METHODS Sedentary normal (cholesterol<200 mg/dL) (n=36) and hypercholesterolemic (cholesterol>220 mg/dL) (n=30) men from the Northern part of Mexico aged 20 to 45 years of age participated in an 8-week study to determine the effects of dietary soluble fiber, either psyllium or oat bran, in lowering plasma LDL cholesterol in this population. Fiber was administered by feeding the subjects an amount of cookies (100 g) equivalent to 1.3 or 2.6 g/day of soluble fiber from psyllium or oat bran, respectively. Subjects were randomly allocated to three groups: a control group consuming cookies with wheat bran, a known source of fiber with no cholesterol lowering effects, psyllium, or oat bran. RESULTS Food frequency questionnaires indicated that subjects from the three groups had similar intakes of foods classified as hypercholesterolemic (p>0.05). Plasma LDL cholesterol concentrations were reduced by an average of 22.6 and 26% in the psyllium and oat bran groups (p<0.001) while a non-significant reduction of 8.4% was observed in the hypercholesterolemic individuals from the control group. No effects on plasma HDL or triglycerides levels were observed among the three dietary treatments except for hypercholesterolemic individuals supplemented with oat bran where a 28% reduction in plasma triglycerides was observed after 8 weeks (p<0.01). CONCLUSIONS These results indicate that psyllium and oat bran are efficacious in lowering plasma LDL cholesterol in both normal and hypercholesterolemic individuals from this population.