Postprandial glycaemic response to white vs granary wholemeal bread in Chinese and Caucasian adults

Previous evidence shows no significant difference in postprandial glycaemic responses (PPGRs) between wholemeal and white bread consumption. This study aimed to investigate whether a commercially available granary wholemeal bread, enriched with dietary fibre, could attenuate PPGRs compared to white bread. The study also explored differences in PPGRs between ethnic groups. Twenty healthy young adults (10 White Caucasian and 10 Chinese participants), with a body mass index (BMI) ranging from 18.5 to 24.9 kg/m², completed the study. Each participant consumed two slices of granary wholemeal bread (fibre: 6.7 g/100 g) or white bread (fibre: 2.7 g/100 g), served with 150 ml of pure orange juice, 10 g of butter, and 15 g of strawberry jam on two separate occasions at least 48 h apart after fasting for 8–12 h. Blood glucose levels were measured via finger prick at fasting (0 min), as well as at 30, 60, 90, and 120 min postprandially using a blood glucose analyser. Participant demographics including age, sex, ethnicity, body weight, height, and body fat percentage were recorded during the first visit. The results showed that both the area under the curve (AUC) and incremental AUC (iAUC) of PPGRs were significantly lower after consumption of granary wholemeal bread compared to white bread (p = 0.027 and p = 0.038, respectively). However, peak glucose values did not differ significantly between bread types. Chinese participants exhibited significantly lower fasting blood glucose levels than White Caucasians (p = 0.033), but no significant ethnic differences were observed in AUC, iAUC, or peak glucose values, regardless of bread type. In conclusion, granary wholemeal bread demonstrated a beneficial effect in reducing PPGRs compared to white bread. Further research is warranted to clarify the role of fibre type and dosage in modulating glycaemic responses and to investigate ethnic variations in PPGRs in larger, well-controlled studies.