June 1, 2009

Carbohydrate: How Much (or Not) to Munch? Dualing Dialog with Tenderich's diabetesmine.com

Warshaw dialogs with diabetesmine.com blogger Tenderich on her blog about research and recommendations about carbohydrate intake for type 1. Check it out, then read my rebuttal below. Thanks Amy for being open to dialog!

As a dietitian and diabetes educator for more years than I like to count, (however, not a person with diabetes), I wanted to provide more context for you to evaluate the research featured in How Many Carbs for Type 1 Diabetics?
My goals are to:
1) provide more study details;
2) present more background on current carbohydrate recommendations from American Diabetes Association (ADA); and
3) provide other ways to control post meal glucose rises rather than restricting carbohydrate intake.
First, to clarify the study (American Journal of Clinical Nutrition (2009;89:1-7) by Linda Delahanty, MS, RD, a leading nutrition researcher, and others. The study population (532 people), were intensively-treated DCCT participants who had dietary data collected through 5 years of follow up. This study is important because it evaluated the association of diet composition and A1C in a well characterized group who had already received extensive diabetes education and had achieved improved glycemic control.
To the study’s key points:

  • Lower carbohydrate intake and higher saturated and total fat intake were associated with higher A1C (worse glycemic control) and independent of exercise, triglyceride levels and body mass index. Participants who consumed a mean carbohydrate intake of 56% of calories had a significantly lower A1C (7.08%) compared to an A1C of 7.47% for participants whose mean carbohydrate intake was 37% of calories.
  • When carbohydrate intake is reduced to manage BG people may increase saturated fat intake (this is due to our limited sources of calories: carbohydrate, protein and fat). (Note: polyunsaturated fats weren’t associated with worse glycemic control.)
  • An important study summary: “…Contrary to commonly reported dietary practices of persons with diabetes who may restrict carbohydrate intake, these results support current recommendations regarding the limitation of saturated fat intake while promoting the consumption of nutrient-dense carbohydrates, such as fruit, whole grains, and vegetables, with appropriate insulin doses as needed.”

With these results in hand consider the desire and need for glycemic control with sufficient carbohydrate consumption for healthy eating. Undoubtedly a challenge!
Now to the 2008 (current) ADA recommendations for carbohydrate of 45 – 65% of calories: This broad recommendation echos the 2005 Dietary Guidelines for Americans (currently undergoing review for fall 2010) and a few key quotes: “Blood glucose is increased in individuals with diabetes in both the fed and fasted state. This abnormal metabolic response is due to insufficient insulin secretion, insulin resistance, or a combination of both. Although dietary carbohydrate increases postprandial glucose levels, avoiding carbohydrate entirely will not return blood glucose levels to the normal range. Additionally, dietary carbohydrate is an important component of a healthy diet. For example, glucose is the primary fuel used by the brain and central nervous system, and foods that contain carbohydrate are important sources of many nutrients, including water-soluble vitamins and minerals as well as fiber. Given the above, low-carbohydrate diets are not recommended in the management of diabetes.”

When it comes down to our sources of calories and putting palatable meals together, we’ve only got foods that contain varying amounts of carbohydrate, protein and fat. (Yes, there’s alcohol, too!) If you try to eat less than 45% of calories as carbohydrate you’ll likely, depending on your calorie intake, eat insufficient amounts (based on nutrient needs) of fruit, whole grains, vegetables, and low-fat dairy foods and may, purely because of the food choices available, eat higher amounts of total fat and saturated fat.

And to my last point, here are a few ways to consider controlling your post meal glucose rises other than restricting healthy carbohydrate-rich foods.

  • Better “questimate” your carb counts (yes, hardly an easy task). Take a look my guest blog From Wild Ass Guesses to Educated Questimates: Practical Pointers to Improve Your Carb Counts for tips .
  • Check out your carbohydrate-to-insulin ratios with post meal checks. Do they need tweeking in general? For certain meals? To control BG rises it’s important to take enough insulin (and to time it to sync with the rise of blood glucose – that’s next). I want to challenge the notion that consistently taking less insulin is positively associated with improved long term health outcomes. I’m not aware of research to this point.
  • Continuous glucose monitoring is providing important learnings about BG excursions. One is that to curtail the post meal rise of BG, as much as is humanly (and safely) possible, give your meal-time rapid-acting insulin a “running start” (10 to 20 min) to cover the BG from food. Reality is that “rapid-acting insulin” isn’t as rapid as we all thought it was.
  • Also keep your ears tuned to the role of gut hormones (GLP-1 and others) and the common deficiency in diabetes of the hormone amylin (co-secreted with insulin from beta cells). These hormones normally play a role in post meal BG control and now that we have pharmaceutical agents (and more to come) it’s a growing area of interest in diabetes care.


Trust me, I recognize (as much as someone without diabetes can) that managing BG excursions is neither simple or easy. I admire each of you for tackling this difficult (and often) frustrating disease each day. Please take a few moments and consider these comments as as you strive for glycemic control and good health.