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Applied carbohydrate counting.

Byline: Lovely Gupta, Deepak Khandelwal and Sanjay Kalra

Abstract

Carbohydrate counting or "carb counting" is a meal planning technique for persons with diabetes for managing blood glucose levels by tracking the grams of carbohydrate consumed at meals. With better patient education and awareness, carb counting has become an important step in diabetes management. People with all types of diabetes can be benefited with this approach via improved glycaemic control and quality of life. In the first part of this review basic principles of carbohydrate counting, its application in clinical practice and exchange lists pertaining primarily to South Asian populations have been discussed. Advanced carb counting involving equations which help in better understanding of insulin-to-carbohydrate ratio and insulin dose adjustment are also included in this review.

Keywords: Carbohydrate counting, Meal-time insulin, Basal insulin, Bolus insulin.

Introduction

Carbohydrates, both simple and complex, greatly affect postprandial blood glucose levels as compared to proteins and fats. Carbohydrate counting or "carb counting" is a meal planning technique for persons with diabetes for managing blood glucose levels by tracking the grams of carbohydrate consumed at meals. Basic carbohydrate counting is a structured approach that emphasizes consistency in the timing and amount of carbohydrate (CHO) consumed.1 This review focusses on advanced carbohydrate counting, which primarily involves matching the amount of CHO consumed with an appropriate dose of insulin (usually rapid acting). It improves glycaemic control and helps in evaluating the impact of CHO intake and food choices on blood glucose and setting nutrition goals.2

Insulin-to-carbohydrate ratio (ICR) and sensitivity factor (SF)

To mimic normal pancreatic function in persons with diabetes, basal insulin is usually given as long acting insulin to counteract rises in blood glucose that occur independent of meal ingestion and bolus insulins are given by either rapid acting (lispro, aspart and glulisine) or regular insulin in relation to meals, which counteracts the rise in blood glucose after meals. Basal insulin requirement is usually constant from day to day and matching bolus insulin to carbohydrate intake using an ICR is optimal for post-meal blood glucose management. Once an ICR is established, patients can adjust their mealtime boluses based on their carbohydrate intake.

Table-1: Equations for advanced carbohydrate counting.4-8

CASE STUDY: A 40 year old man with diabetes

###Height###: 5'8" (172 cm)

###Weight###: 72.5 kg

###BMI###: 24.57 kg/m2

###Daily energy intake : 1600 kcal

###Carbohydrate###: 55% = 880 kcal i.e. 220gm

###Protein###: 20% = 320 kcal i.e. 80 gm

###Fat###: 25% = 400 kcal i.e. 44 gm

1. Calculating Total Daily Insulin dose (TDI)

* TDI = 0.55 Weight in kg

###So, 0.55 72.5 = 40 units of insulin/day

2. Calculating Basal and Bolus Insulin dose

* Bolus Insulin dose = 50% of TDI

###So, 50% of 40 units = 20 units to cover total mealtime CHO/day

3. Calculating ICR / CHO Coverage Dose

By 450/500 Rule

* 500 Rule for Users of aspart, lispro and glulisine

* 500 TDI = grams of carbohydrate that are approximately covered by 1 unit of

###insulin

###So, 500 40 = 12.5

###i.e. 1 unit of insulin will cover approximately 12.5 grams of carbohydrate

* 450 Rule for Users of Regular Insulin

* 450 TDI = grams of carbohydrate that are approximately covered by 1 unit of

###insulin

###So, 450 40 = 11.2

###i.e. 1 unit of insulin will cover approximately 11.2 grams of carbohydrate

By Body weight

###2.8 body weight (in pounds) TDI

###So, 2.8 (72.5 kg 2.2) TDI

###2.8 159.5 lb 40 = 11

###i.e. 1 unit of insulin will cover approximately 11.2 grams of carbohydrate

4. Calculating CHO coverage at particular meals

* Total grams of CHO in the meal grams of CHO disposed by 1 unit of insulin

###So, 55 gm 12 = 4.5 i.e. 5 approx.

Meals###Early###Breakfast###Mid-###Lunch###Evening###Dinner###Post-

###morning###morning###snack###dinner

Percent of total CHO/d###10%###20%###5%###25%###10%###25%###5%

Grams of total CHO/d###22gm###44gm###11gm###55gm###22gm###55gm###11gm

Bolus Insulin dose (20)

to cover meal-time CHO###55 gm 12###80 gm 12###66 gm 12

###5-6 units###6-7 units###5-6 units

*Approximately, 6-7 units of bolus insulin before each major meal (TDS insulin

regimen) to cover 20 units of bolus insulin i.e. short or rapid acting insulin/d and 20

units of basal insulin i.e. long acting insulin/d.

Applied carbohydrate counting

5. Calculating Correction Factor (CF)

* CF = 1700/1800 TDI

###So, 1700 40 = 42.5

###1800 40 = 45

###1 unit of insulin will drop blood glucose level by 45 mg/dl (40-50 mg/dl)

* Difference between actual blood glucose level and target blood glucose level correction factor

###So, Actual blood glucose level before breakfast = 220

###Target blood glucose level before breakfast = 130

###220 - 130 45 = 2 units

###Total dose before breakfast = CHO insulin dose (step 4) + 2 units

###Using CF, total meal-time insulin dose is 6 units+ 2 units = 8 units

Table-2: Limitations of CHO counting in clinical practice.7

###Approach related###Individual related

* It is a tool for improvement but not###* Individual insulin sensitivity and

the solution for people with diabetes###insulin resistance is not considered

* Primarily used for carbohydrate based###* Lean, newly diagnosed and insulin

diet###sensitive patients may calculate higher

* Does not consider nutrients like###doses of insulin

protein, fat, vitamins and minerals###* Obese and insulin resistant patients

obtained from food items###may calculate lower doses of insulin

* Not a holistic approach as it does not###* Inappropriate determination of

take account exchange list of other food###quantity of carbohydrate containment

groups###or portion size

* Only tentative idea of total daily###* Professional dieticians may be

insulin dose and may need changes later###required to calculate amount and type of

* Assumes constant response to insulin###CHO in the diet

throughout the day###* May result in inappropriate calorie

###intake or insulin dose

Every person responds differently to insulin. For most adults, one unit of rapid-acting insulin can usually cover 15 grams of CHO. A toddler may require 1/2 to 1 unit of rapid-acting or regular insulin for 30 to 45 grams of CHO, while a teenager may require 1 unit for each 7 to 15 grams of CHO. Also, it may further differ in pregnancy. However, other factors such as weight, activity level, gender and hormonal changes also determine the ICR.3,4

A premeal blood glucose level determines whether additional insulin should be added to the premeal bolus to cover premeal blood glucose excursions using a sensitivity factor (SF). It helps to bring high blood glucose levels to the target blood glucose levels. Blood glucose readings are taken following a meal (about two hours after starting meal) to assess the ICR. As the ICR is determined to be correct, postmeal readings can then be taken periodically as needed.

For better understanding, Table-1 discusses some quick equations with respective illustrations with a case study. Some limitations of CHO counting are summarized in Table-2.

Conclusion

Judicious calculations of ICR and SF, regular follow-ups and appropriate monitoring based on individual requirements with timely modifications of insulin doses makes it a helpful approach for the people with diabetes to develop an understanding of the principles of the basal-bolus insulin concept to achieve optimal blood glucose levels.

References

1. Chiesa G, Piscopo MA, Rigamonti A, Azzinari A, Bettini S, Bonfanti R, Viscardi M, Meschi F, Chiumello G. Insulin therapy and carbohydrate counting. Acta Biomed. 2005; 76 Suppl 3: 44-8.

2. Gupta L, Khandelwal D, Singla R, Gupta P, Kalra S. Pragmatic dietary advice for diabetes during Navratris. Indian J Endocrinol Metab. 2017; 21: 231-237.

3. Mehta SN, Quinn N, Volkening LK, Laffel LM. Impact of carbohydrate counting on glycemic control in children with type 1 diabetes. Diabetes Care. 2009; 32: 1014-6.

4. Kulkarni KD. Carbohydrate Counting: A Practical Meal-Planning Option for People with Diabetes. Clin diabetes. 2005; 23: 120-2.

5. Dungan KM, Sagrilla C, Abdel-Rasoul M, Osei K. Prandial insulin dosing using the carbohydrate counting technique in hospitalized patients with type 2 diabetes. Diabetes Care. 2013; 36: 3476-82.

6. Bergenstal RM, Johnson M, Powers MA, Wynne A, Vlajnic A, Hollander P, Rendell M. Adjust to target in type 2 diabetes: comparison of a simple algorithm with carbohydrate counting for adjustment of mealtime insulin glulisine. Diabetes Care. 2008; 31: 1305-10.

7. Lopes Souto D, Lopes Rosado E. Use of carb counting in the dietary treatment of diabetes mellitus. Nutr Hosp. 2010 ; 25: 18-25.

8. Masood SN, Masood Y, Naim U, Razzak SA. Antenatal management of pregnancy complicated by diabetes. J Pak Med Assoc. 2016; 66(9 Suppl 1): S 69-73.
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Publication:Journal of Pakistan Medical Association
Date:Sep 28, 2017
Words:1649
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