Digestibility of carbohydrates from rice-, oat- and wheat-based ready-to-eat breakfast cereals in children

OBJECTIVE: To study the effect of the presence and quality of dietary fibre in ready-to-eat (RTE) breakfast cereals on completeness of carbohydrate digestion in children and on starch susceptibility to alpha-amylase in vitro. DESIGN: A controlled intervention study. SUBJECTS: Eight 3-8-year-old healthy children. INTERVENTIONS: Completeness of digestion was evaluated by assessing the amount of carbohydrates apparently fermented into the colon using the breath-H2 technique after consumption in random order, of five breakfast tests containing boiled rice (either alone or supplemented with 3 g of lactulose) as reference food, or RTE cereals based on rice (low-fibre), wheat (high insoluble fibre) and oats (high-soluble fibre). The potential glycaemic impact of the products was estimated in vitro by assessing starch susceptibility to alpha-amylolysis using an enzymatic-dialysis method. RESULTS: Compared to boiled rice and to rice-based RTE cereal, wheat- and oat-based RTE cereals both significantly (P < 0.05) increased the amount of apparently fermented carbohydrates (+1.1 +/- 1.7% of total breakfast carbohydrate fermented for rice, +5.6 +/- 0.9% for wheat and +9.4 +/- 3.7% for oats; mean +/- SEM), calculated using the excess H2 in breath after lactulose as standard. All products showed similar in vitro digestibility, resulting in estimated glycaemic indexes of 117.5 (24.0) for rice, and 105.7 (14.1) for oats-based, 128.4 (17.6) for wheat-based, and 129.8 (16.6) [mean 95% CI)] for rice-based RTE cereals. CONCLUSIONS: Results suggest that the presence of fibre in RTE breakfast cereals, in particular soluble fibre, increases colonic fermentation in children whereas it seems not to affect glucose availability.