Fructose may beat other carbohydrates for lowering glycated blood proteins

Consuming fructose in place of other carbohydrates lowers glycated blood proteins by a clinically significant percentage, a recent meta-analysis suggests.

Canadian researchers conducted a systematic review and meta-analysis of controlled feeding trials that lasted at least seven days in individuals with diabetes. After exclusions, they had 18 trials and 209 subjects from which to assess the effects of isocaloric exchange of oral fructose for other sources of carbohydrates. Glycemic control marker outcomes included fasting glucose, fasting insulin, and glycated blood proteins (hemoglobin A1c [HbA1c], albumin, and fructosamine). Results were published in July's Diabetes Care.

Researchers made 13 glycated blood protein comparisons among 172 subjects with type 1, type 2 or undifferentiated diabetes. Starch (77%) and sucrose (7.7%) were used as carbohydrate comparisons, with one trial using both. Replacing these carbohydrates with fructose significantly reduced the percentage of glycated blood proteins (standard mean difference, −0.27; P=0.02), with significant intertrial heterogeneity (I² statistic=63%; P=0.001). The reduction was equivalent to an approximate 0.53% decrease in HbA1c. There were no significant effects on fasting glucose (16 comparisons, n=176) or fasting insulin (7 comparisons, n=57).

The 0.53% reduction with fructose is clinically significant, as it “exceeds the clinically meaningful threshold of ≥0.3% proposed by the U.S. Food and Drug Administration for the development of new drugs for diabetes and lies at the lower limit of efficacy expected for oral hypoglycemic agents,” the researchers wrote. The benefit was seen across a dose range of 20 to 160 g/d. A dose threshold for harm needs to be considered, they added, because previous research has shown fructose may increase serum triglycerides more than other carbohydrates at doses above 60 g/d. Since most of the trials in the current meta-analysis had short follow-up, small sample size and poor quality, more studies are needed that weigh the potential glycemic benefit of fructose against adverse metabolic effects, they concluded.