A comparison between whole grain and pearled oats: acute postprandial glycaemic responses and in vitro carbohydrate digestion in healthy subjects.

PURPOSE

To compare the glycaemic response of whole grain oat kernels and pearled oats cooked under normal pressure or higher pressure and examine whether replacing half of the rice in a given meal with either of the two oat grains could make a difference in acute glycaemic responses.

METHODS

In a randomised crossover trial, ten healthy subjects consumed two groups of test meals: (1) oat grain-only, including whole grain oats cooked under normal pressure (WONP) and higher pressure (WOHP) as well as their pearled oat counterparts, PONP and POHP; and (2) mixed meals of aforementioned oat grains and cooked rice (OG + R), including WONP + R, WOHP + R, PONP + R and POHP + R. A postprandial blood glucose test, texture profile analysis and in vitro carbohydrate digestion assay were carried out for each test meal.

RESULTS

Compared with the rice reference, oat grain-only meals induced lower glucose levels at all time points, lower peak values and smaller glucose excursions at 120 min (P < 0.05), but OG + Rs did not have the abovementioned effects. The oat grain-only meals had glycaemic indexes (GIs) ranging from 51 to 58, while those of OG + Rs ranged from 59 to 70. WONP + R had a 21% lower iAUC and a 40% lower iAUC value than those of rice (P < 0.05). Oat-rice mixed meals had lower iAUC values compared with that of the rice control (P < 0.05), except for POHP + R. Excellent consistency between the hydrolysis index and the GI was observed (r = 0.969, P < 0.001) in oat grain-only meals.

CONCLUSIONS

All oat grain-only meals could be included in the glycaemic management diet, regardless of the oat grain type or cooking treatment. In oat-rice mixed meals, whole grain oats and normal pressure cooking ensured a favourable glycaemic effect.