Milk thistle contains silybin, which is a potential iron chelator. We aimed to determine whether silybin reduced iron absorption in patients with hereditary haemochromatosis. In this crossover study, on three separate occasions, 10 patients who were homozygous for the C282Y mutation in the HFE gene (and fully treated) consumed a vegetarian meal containing 13.9 mg iron with: 200 ml water; 200 ml water and 140 mg silybin (Legalon Forte); or 200 ml tea. Blood was drawn once before, then 0.5, 1, 2, 3 and 4 h after the meal. Consumption of silybin with a meal resulted in a reduction in the postprandial increase in serum iron (AUC±s.e.) compared with water (silybin 1726.6±346.8 versus water 2988.8±167; P<0.05) and tea (silybin 1726.6±346.8 versus tea 2099.3±223.3; P<0.05). In conclusion, silybin has the potential to reduce iron absorption, and this deserves further investigation, as silybin could be an adjunct in the treatment of haemochromatosis.