Carbohydrate Counting 101

Carbohydrate counting is a relatively new approach to meal planning for persons with Type 1 or Type 2 diabetes. It allows for more flexibility in meal planning than does the former exchange system.

The rationale for carbohydrate counting is that carbohydrate is the principle nutrient that will raise blood glucose levels, so focusing on the amount of carbohydrate consumed (as measured in grams) will lead to better postprandial blood glucose readings.

It is well known that carbohydrate begins to raise blood glucose levels within 15 minutes of consumption and that carbohydrate is converted to nearly 100% glucose generally within two hours of consumption. (1) Factors that can slow the rate of absorption include a high fat meal, a high protein meal and gastroparesis. (2)

There are two types of carbohydrate counting available to patients. The first, Basic Carbohydrate Counting, is helpful for both Type 1 and Type 2 patients. The second option, which builds from the first, is called Advanced Carbohydrate Counting. It is best used for Type 1 patients on multiple daily insulin injections or for those patients using Continuous Subcutaneous Insulin Infusion (CSII - an insulin pump).

Basic Carbohydrate Counting

Patients interested in carbohydrate counting should be referred to a dietitian. At the first session with the dietitian, a nutritional assessment is necessary. An assessment of intake of the individual's carbohydrate as well as other nutrients is determined. At this visit, the patient is educated about:

• What constitutes a healthy diet
• The sources of carbohydrate in the diet
• How to read labels, interpret portion sizes, and count grams of carbohydrate correctly (see Additional Resources)
• How to accurately record intake of carbohydrate consumed.

A number of exercises are done to help the patient become comfortable with carbohydrate counting. The emphasis is on identification and recording of carbohydrate and on the recording of blood glucose.

A second session is necessary to:

• Review the food record and assess the amount of carbohydrate being consumed,
• Look at the times of the day and see if the carbohydrate intake varies at meals
• Assess whether the carbohydrate intake at a particular meal varies from day to day
• Set goals for carbohydrate intake to be consistent at each meal and snack time. These goals are based on usual carbohydrate intake, medication and level of physical activity. In most cases, once set and followed, consistent carbohydrate intake has been shown to greatly reduce variability in postprandial blood glucose levels and improve overall glycemic control. (4 ).

Basic carbohydrate counting focuses on the amount, rather than the source, of carbohydrate consumed. This allows a patient to enjoy "treats" occasionally without the guilt and worry that they will negatively impact blood glucose. That being said, the importance of a healthy diet is still emphasized.

Pre-requisite to successful Basic Carbohydrate Counting

• Perform simple addition and subtraction
• Have and accurately use measuring utensils like measuring cups and spoons
• Accurately read and interpret the Nutrition Facts Table and other resources provided to the patient
• Measure and record blood glucose
• Accurately record food intake, physical activity and stressors.

Advanced Carbohydrate Counting

Advanced carbohydrate counting builds on the skills of basic carbohydrate counting. It is recommended for patients with diabetes who are on intensive insulin therapy or for those on the insulin pump. Advanced carbohydrate counting involves an understanding of the relationship between nutrition, activity level and blood glucose.(1,2,4,5) It teaches the patient to consider carbohydrate intake, activity level as well as current blood glucose levels in determining insulin needs. It involves the use of Insulin to Carbohydrate Ratios and Insulin Sensitivity Factor in controlling blood glucose levels.

Insulin to Carbohydrate Ratio (I:CHO Ratio)

Insulin to carbohydrate ratio is a formula that predicts how many grams of carbohydrate are covered by one unit of insulin. It is written as insulin: g carb

For example, a 1:15 ratio means that a person should take 1 unit of insulin for every 15 grams of carbohydrate consumed at the meal. Blood tests ac and 2 hour pc will determine if this ratio is appropriate. The 2-hour pc level should be 1-2 mmol/L higher if the ratio is appropriate.

The Insulin to Carbohydrate ratio is determined using the formula
500 ÷ Total daily dose of insulin

This formula is most accurate when glucose is in target range.

Example:
Sue takes a total of 40 units per day and her glucose is in target range. Her ratio is calculated as:

500 divided by 40 = 12.5. She therefore should take one unit of insulin for every 12.5 grams of carbohydrate (1:12.5). If her meal has 50 grams of carbohydrate, she will need to take 4 units of insulin.

Insulin Sensitivity Factor (ISF)

Insulin sensitivity factor is a measure of expected glucose drop in mmol/L from taking 1 unit of insulin. It is determined by the formula
100 ÷ total daily dose of insulin

Example:
Sue takes 40 units a day, her sensitivity is 100 divided by 40 = 2.5. (ISF is 2.5). If she wants to bring her blood sugar from 15mmol/l to 10mmol/l (a 5 mmol/L drop) she will require 5 divided by ISF of 2.5 = 2 units of insulin.

Advanced carbohydrate counting also teaches the patient to adjust insulin for exercise and other circumstances that may alter the dose or timing of insulin, such as a high fat or high protein meal, sick days, stress, and alcohol.

• Mastery of basic carbohydrate counting
• An insulin regime conducive to insulin adjustments such as intensive insulin therapy or insulin pump therapy
• More complex math skills
• A willingness to check blood glucose ac, 2-hour pc and hs and record these values
• An ability to make informed decisions.

One benefit of advanced carbohydrate counting is a greater flexibility in carbohydrate intake without a negative impact on blood glucose. With advanced carbohydrate counting, consistency in carbohydrate intake is not necessary. This system is very helpful to many patients but can be particularly helpful for those on shift-work or those with appetites that vary.

Other benefits of advanced carbohydrate counting include better glycemic control and more simplified meal planning. Although this initially requires a lot of "homework", most people do well and see positive results and a normalization of lifestyle with a demanding disease.

- Rose Teasdale, Staff Dietitian
Diabetic Clinic, St. Martha's Regional Hospital

1. Warshaw, Hope S.,Bolderman,K.M..Practical Carbohydrate Counting A How-to-teach Guide for Health Professionals. American Diabetes Association, 2001.
2. Diabetes Health Center. CHO Counting and CSII for Health Professionals. Disetronis. 1994
3. Canadian Diabetes Association. Beyond the Basics: Meal Planning For Healthy Eating, Diabetes Prevention & Management. Canadian Diabetes Association, 2006.
4. Franz, Marion J, Karmeen Kulkarni, et al.A Core Curriculum for Diabetes Education - Nutrition Therapy. American Association of Diabetes Educators.
5. Lightfoot, Claire, Pytka,E. Making Carbs Count: Advanced Carbohydrate Counting for Intensive Diabetes Management. Canadian Diabetes Association.

• Nutrition Labelling Education Centre
• Canadian Diabetes Association
• Dietitians of Canada

You can search for abstracts of the above references by following this link: PubMed