We evaluated decreases in glycosylated hemoglobin (HbA1c) achieved by reducing carbohydrate from various sources in type 2 diabetes mellitus patients.

We followed up 138 male and 107 female outpatients on a moderate low-carbohydrate diet without diabetic medication for 6 months. Changes in carbohydrate sources (Δcarbohydrate) were assessed from 3-day dietary records at baseline and 6 months, and associations with changes in HbA1c (ΔHbA1c) were examined with Spearman's correlation coefficients (r_s) and multiple regression analysis.

ΔHbA1c was −1.5%±1.6% in men and −0.9%±1.3% in women, while Δtotal carbohydrate was −115.3±103.7 g/day in men and −63.6±71.1 g/day in women. Positive associations with ΔHbA1c were found for Δtotal carbohydrate (r_s=0.584), Δcarbohydrate from soft drinks (0.368), confectionery (0.361), rice (0.325), bread (0.221), Chinese soup noodles (0.199) in men, and Δtotal carbohydrate (0.547) and Δcarbohydrate from rice (0.376) and confectionery (0.195) in women. Reducing carbohydrate sources by 50 g achieved decreases in HbA1c of 0.43% for total carbohydrate, 1.33% for soft drinks, 0.88% for confectionery, 0.63% for bread, 0.82% for Chinese soup noodles and 0.34% for rice in men and 0.45% for total carbohydrate, 0.67% for confectionery and 0.34% for rice in women, although mean reductions in carbohydrate from these sources were much smaller than that from rice.

Decreases in HbA1c achieved by reducing carbohydrate from soft drinks, confectionery, bread and Chinese soup noodles were 2- to 4-fold greater than that for rice. Our results will enable patients to decrease HbA1c efficiently (UMIN000009866).