OBJECTIVE: To examine whether a worksite nutrition programme using a low-fat vegan diet could significantly improve nutritional intake. DESIGN: At two corporate sites of the Government Employees Insurance Company, employees who were either overweight (BMI > or = 25 kg/m2) and/or had type 2 diabetes participated in a 22-week worksite-based dietary intervention study. SETTING: At the intervention site, participants were asked to follow a low-fat vegan diet and participate in weekly group meetings that included instruction and group support (intervention group). At the control site, participants received no instruction (control group). At weeks 0 and 22, participants completed 3 d dietary records to assess energy and nutrient intake. SUBJECTS: A total of 109 participants (sixty-five intervention and forty-four control). RESULTS: In the intervention group, reported intake of total fat, trans fat, saturated fat and cholesterol decreased significantly (P < or = 0.001), as did energy and protein (P = 0.01), and vitamin B12 (P = 0.002), compared with the control group. Intake (exclusive of any use of nutritional supplements) of carbohydrate, fibre, vitamin C, magnesium and potassium increased significantly (P < or = 0.0001), as did that for beta-carotene (P = 0.0004), total vitamin A activity (P = 0.004), vitamin K (P = 0.01) and sodium (P = 0.04) in the intervention group, compared with the control group. CONCLUSIONS: The present study suggests that a worksite vegan nutrition programme increases intakes of protective nutrients, such as fibre, folate and vitamin C, and decreases intakes of total fat, saturated fat and cholesterol.