I believe fructose, a monosaccharide commonly maligned around the internet, shows some promise as a dietary adjunct to treat type 2 diabetes. Several diet trials have been conducted which demonstrated its beneficial effects on this population.
In a 9 week study on ambulatory type 2 diabetics, 60 grams of crystalline fructose was added to the diet of one group and was not added to the diet of the other group (1). By the end of the trail the 9 diabetics given fructose experienced a significant decrease in fasting blood glucose and glycosylated hemoglobin, while the other group saw these values increase non-significantly. Serum LDL, HDL, and triglycerides were unchained in the fructose group, while triglycerides increased in the other group.
In another study with a crossover design, 12 diabetics were fed 21-23% of their dietary calories as either fructose, sucrose, or starch (2). After 8 days the fructose diet resulted in lower one and two hour post meal glucose levels, lower overall blood glucose levels, and less urinary glucose excretion in both the type 1 and type 2 diabetics. Triglyceride levels were not different between groups. A similar 28 day study on 18 diabetics by the same researchers who performed the previous study found that obtaining 20% of calories from fructose compared to starch led to a 12.5% decrease in plasma glucose levels, a decrease in glycated albumin in the T1 diabetics, and a decrease in urinary glucose (6).
In a 4 week study on 10 type 2 diabetics the effect of about 45-65 grams of fructose or a placebo were tested (3). At the end of the trail the fructose group saw a decrease in HbA1c and improved insulin sensitivity (a not-to-shabby 34 percent increase), while the control group saw no difference on these parameters. Serum triglycerides remained unchanged. A similar study, also lasting 4 weeks, also on 10 T2 diabetics (non-insulin dependent) found that replacing 25% of the subjects dietary carbohydrates with fructose led to lower blood glucose levels following an oral glucose tolerance test (5).
Finally, the longest study of the bunch was another crossover study in which 13 poorly controlled type 2 diabetics either consumed 60 grams of fructose (contributing 15% of their total calories) or didn’t for 6 months, at which time they switched groups (4). After half a year, the diet with the added fructose saw serum glucose and glycosylated hemoglobin decrease significantly while the control diet saw both of these values increase non-significantly. No negative effects of fructose on serum lipids were observed.
Finally, a study on 14 diabetic men found that adding 50-60 grams of fructose to their diet in a hospital setting led to lower fasting plasma glucose levels (7).
None of this means these effects will be seen in normoglycemic people, I just wanted to point out how fructose affects diabetics since I rarely hear people point this out.
For some of the reasons behind why fructose may be beneficial to diabetics, see this blog post by Andrew Kim: