CHICAGO — The standard practice of counting carbohydrates to better manage postprandial glycemic control in type 1 diabetes may not have substantial evidence behind it, researchers reported here.
In a review and meta-analysis of six randomized, controlled trials, carbohydrate counting slightly improved glycemic control with a mean drop in glycated hemoglobin (HbA1c) of -0.3%, but it wasn’t significant (P=0.185), Kirstine Bell, a PhD candidate at the University of Sydney, reported at the American Diabetes Association meeting.
“There’s limited evidence to recommend carbohydrate counting over other dietary interventions for improving glucose control in type 1 diabetes,” Bell said. “And it’s concerning that there are only six studies that could be identified when this is such an integral element of diabetes management in type 1 diabetes. It affects the management of millions of people around the world.”
Carbohydrate counting is the best known method for matching insulin dosing to meals, and is the recommended dietary strategy for achieving glycemic control in type 1 diabetes, though that recommendation has been largely based on expert consensus, Bell said.
To assess the state of the literature, she and colleagues conducted a review and meta-analysis of carbohydrate counting trials in adults and children with type 1 diabetes. They ultimately included six studies with a total of 563 adults and 104 children conducted between January 1980 and April 2012.
Overall, there were five adult studies and one pediatric trail that included children, ages 8 to 13. Five trials had a parallel group design while one involved a cross-over.
All trials lasted at least 3 months and compared carbohydrate counting with usual care, which consisted of either general nutrition advice or low dietary glycemic index (GI) advice.
For their analysis, Bell and colleagues set the primary outcome of change in HbA1c, and secondary outcomes included hypoglycemia, insulin dose, weight change, fasting plasma glucose, and quality of life.
Studies were generally of good to high quality, with an overall quality score of 7.7 out of 13, the researchers reported.
Bell and colleagues found a decrease in mean HbA1c with carbohydrate counting compared with usual care (-0.3%), but it wasn’t significant (P=0.185).
They were unable to conduct an analysis of secondary outcomes because of the low number of studies and inconsistencies in their reporting metrics.
They did, however, find a trend toward reduced risk of hypoglycemia and improved quality of life with carbohydrate counting.
On the other hand, there were no changes in insulin dosing, weight, or fasting plasma glucose.
Bell cautioned that the efficacy of carbohydrate counting may be limited by patients’ ability and commitment to managing their diet. Studies have shown that greater accuracy and precision in carbohydrate counting have been associated with greater declines in HbA1c, she said.
Jay Skyler, MD, of the University of Miami told MedPage Today that this is likely the case in the current analysis.
“Carb counting works for those who are vigilant, but has little impact in studies because most folks are not vigilant,” said Skyler who was not involved in the study.
Bell also noted that the lack of benefit seen in her meta-analysis may not be due to carbohydrate counting itself, given that many patients with type 1 diabetes have difficulty managing their postprandial blood glucose levels for other reasons.
Indeed, some work has shown that having any prescribed meal plan — whether it restricts carbohydrates significantly or not — has been associated with lower HbA1c levels.
Also, work has shown that carbohydrate counting may lead to unhealthy eating, not only for its reliance on packaged foods which make counting nutrients easier, but also because of the potential for exceeding dietary recommendations on other nutrients including fats and proteins.
“As clinicians, we need to make sure that healthy eating is still the basis for meal planning and insulin matched to food choices, rather than food choices being made to either avoid carbohydrates or insulin,” Bell said.
She concluded that her study suggests the evidence to recommend carbohydrate counting as standard therapy in type 1 diabetes glycemic management is limited, and more work needs to be done. However, she acknowledged that carbohydrate counting is so routine in practice, finding a control group would be challenging.
“It’s still the best known method for matching insulin to meals,” she concluded, “but our study highlights the need for further research.”