Research on Carb Counting

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For what seems like ages, carbohydrate counting has been the standard way to calculate mealtime insulin doses for people with diabetes who take insulin. By applying your personal insulin-to-carbohydrate ratio and taking your premeal blood glucose level into account, counting carbs can help you dose your insulin to achieve tight blood glucose control while minimizing the risk of hypoglycemia (low blood glucose). Carb counting has spread beyond just people who take insulin; it is now widely used as a general meal-planning tool for people with diabetes.

But according to a recent review of research on the subject, counting carbs may not live up to its reputation when it comes to blood glucose control. Published late last month by The Lancet Diabetes & Endocrinology, the review sifted through 311 studies to find seven that lasted at least three months and compared carb counting with “general or alternate dietary advice” in people with Type 1 diabetes. According to an article on the review by MedPage Today, five of the previously published studies found carb counting to result in lower HbA1c levels (a measure of long-term blood glucose control) by an average of 0.64%, while two studies found that alternative, rougher methods of calculating insulin doses worked just as well or better. When data from all seven studies were combined — resulting in a subject pool of 599 adults and 104 children with Type 1 diabetes — there was no significant difference in HbA1c between participants who were assigned to count carbs and those assigned to other methods.

As we noted in a post here at Diabetes Flashpoints two years ago, alternative ways to regulate carbohydrate in the diet include the glycemic index (GI), which rates carbohydrate-containing foods according to how quickly they raise blood glucose, and the diabetic exchange system. Very few studies, however, have compared these or any other alternative systems with carb counting. A 2003 meta-analysis (combined analysis of several studies) did, however, find an average HbA1c reduction of 0.43% associated with low-GI diets. HbA1c is, of course, not the only outcome that matters to many people: A 2008 study found that low-GI diets resulted in fewer and lower doses of diabetes drugs being prescribed, while a 2011 study found that carb counting led to a lower body-mass index (BMI) among insulin pump users than estimating mealtime insulin without counting carbs.

What do you think — has counting carbs worked for you? Have you ever compared carb counting with other methods, such as estimating carbs for insulin doses or focusing on a low-GI or low-carb diet? Do you find counting carbs to be difficult or cumbersome? If you count carbs, do you take other dietary factors, such as fat or fiber content, into account when calculating an insulin dose? Leave a comment below!

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