There were a total of 10 serious adverse events (SAE) recorded over the study period: six in the placebo group and four in the chitosan group ( P ¼ 0.53, Table 4). The SAE were defined as hospitalisations (three in the chitosan group, four in the placebo group, P ¼ 0.71), cancer incidence (one in the chitosan group, three in the placebo group, P ¼ 0.34) and one death (placebo group). Of the nonserious adverse events, 36 volunteers in the chitosan group and 19 in the placebo group reported noninfectious gastrointestinal side effects (defined as abdominal pain, bloating, constipation, indigestion, or non-infectious diarrhoea) (P ¼ 0.02). There were no significant differences between intervention groups in any other category of nonserious adverse events.