The safety and tolerability of ispaghula husk, which can now be used as an adjunct to diet for the treatment of mild-to-moderate hypercholesterolaemia, was assessed in 93 healthy subjects over a 52-week period. The study looked at the nutritional, biochemical, and haematological effects of ispaghula. Over the study period there were small but statistically significant changes in some measurements of minerals and vitamin levels, and in some haematological and biochemical parameters. However, none of these were of clinical significance, with the possible exception of changes in vitamin B12 levels. A daily dose of 10.5 g ispaghula was well tolerated and the majority of adverse events recorded were minor, of short duration and either unrelated or possibly related to the study treatment. The results suggest that ispaghula husk can be used with confidence for the long-term treatment of mild-to-moderate hypercholesterolaemia.