A. Rebecca Stanski, a dietetic intern at Tufts Frances Stern Nutrition Center, replies: In a sense, the medical team was both correct and incorrect. When we talk about diabetes management through diet, we focus on carbohydrates, the main macronutrient that affects blood sugar. A common strategy is carbohydrate counting, which allows diabetics to know the quantity of carbohydrates they are consuming at each meal or snack. Carbohydrate counting can help type 1 diabetics know how much insulin to take and can help type 2 diabetics consume consistent carbohydrates throughout the day for more stable blood sugar levels.
For type 1 diabetics, it is true that a carb is a carb and that only the quantity, not the source, of carbohydrates matters. For example, if a type 1 diabetic consumes 15 grams of total carbohydrate from candy (a simple/refined carbohydrate source) or 15 grams from brown rice (a complex carbohydrate source), the person is going to take the same amount of insulin, although timing may be different.
But there is also the fiber rule. Since fiber is not broken down into glucose, the grams of fiber in a food should be subtracted from the grams of total carbohydrate. For example, if a piece of whole-grain bread has 24 grams total carbohydrate and 4 grams fiber, the amount of available carbohydrate to be counted is 20 grams. Fiber slows the rate of digestion, so a high-fiber source would have a slower, more stable impact on blood sugar. Fiber also increases satiety, which may deter a diabetic from over-consuming carbohydrates. Additionally, whole grains and complex carbohydrates like vegetables have other health benefits such as higher nutrient content, reduced risk of heart disease, proper bowel function, and weight management.