Patient information: Type 1 diabetes mellitus and diet

TYPE 1 DIABETES OVERVIEW

Diet and physical activity are critically important in the management of the ABCs (A1C, Blood pressure and Cholesterol) of type 1 diabetes. To effectively manage A1C (hemoglobin A1c) and achieve stable blood sugar control, it is important to understand to understand how to balance food intake, physical activity, and insulin.
Making healthy food choices every day has both immediate and long-term effects. With education, practice, and assistance from a dietitian and/or a diabetes educator, it is possible to eat well and control diabetes.
This topic discusses how to manage diet in people with type 1 diabetes. The role of diet and activity in managing blood pressure and cholesterol is reviewed separately. (See "Patient information: High blood pressure, diet, and weight" and "Patient information: High cholesterol and lipids (hyperlipidemia)".)

WHY IS DIET IMPORTANT?

Many factors affect how well diabetes is controlled. Many of these factors are controlled by the patient, including how much and what is eaten, how frequently the blood sugar is monitored, physical activity levels, and accuracy and consistency of medication dosing. Even small changes can affect blood sugar control.
Eating a consistent amount of food every day and taking medications as directed can greatly improve blood sugar control and decrease the risk of diabetes-related complications, such as coronary artery disease, kidney disease, and nerve damage. In addition, these measures impact weight control. A dietitian can help to create a food plan that is tailored to your medical needs, lifestyle, and personal preferences.

TYPE 1 DIABETES AND MEAL TIMING

Consistently eating at the same times every day is important for some people, especially those who take long-acting insulin (eg, NPH). If a meal is skipped or delayed, you are at risk for developing low blood glucose.
People who use intensive insulin therapy (those on an insulin pump or multiple daily insulin injections) have more flexibility around meal timing. With these regimens, skipping or delaying a meal does not usually increase the risk of low blood sugar.

High fat meals — Foods or meals that are high in fat (eg, pizza) may be eaten occasionally, although blood glucose levels should be monitored more closely. High-fat meals are broken down more slowly than low-fat meals. When using rapid acting insulin (eg, Humalog, Novolog) before a meal, the blood sugar level may become low shortly after eating and then rise hours later.

People who use an insulin pump can use an extended insulin delivery regimen to better manage blood sugar levels after eating a high-fat meal. People who give insulin injections do not generally adjust their treatment based upon the fat content of their meal.

TYPE 1 DIABETES AND CARBOHYDRATE CONSISTENCY

Carbohydrates are the main energy source in the diet, and include starches, vegetables, fruits, dairy products and sugars. Most meats and fats do not contain any carbohydrates.
Carbohydrates have a direct impact on the blood sugar level whereas proteins and fat have little to no impact. Eating a consistent amount of carbohydrates at each meal can help to control blood sugar levels, especially if you take long-acting insulin (eg, NPH).
There are several ways to calculate carbohydrate content of a meal, including carbohydrate counting and exchange planning.

Carbohydrate counting — A dietitian usually helps to determine the number of carbohydrates needed at each meal and snack, based upon your usual eating habits, insulin regimen, body weight, nutritional goals, and activity level. In most people, between 45 and 65 percent of the day's total calories should come from carbohydrates.

The way carbohydrates are divided up for each meal or snack is based upon personal preferences, meal timing and spacing, and type of insulin regimen (table 1).
The number of carbohydrates in a food can be determined by reading the nutrition label, consulting a reference book or website, or carrying a database on a personal digital assistant (PDA). Restaurants usually have this information available upon request. (See 'Where to get more information' below.)
It is important to note the serving size and grams of fiber when calculating carbohydrates. Eating more than one serving will increase the number of calories consumed and the dose of insulin needed to cover the meal. For example, some pre-packaged snacks contain 2 or more servings. To calculate the carbohydrate content of the entire package, multiply the number of servings by the number of carbohydrates.
When a serving of food has more than 5 grams of fiber, the grams of fiber should be subtracted from the grams of carbohydrates to calculate the insulin dose (figure 1) [1].

Intensive insulin therapy — People who use an insulin pump or take multiple injections of rapid-acting insulin per day can adjust their pre-meal insulin dose based upon the number of carbohydrates they plan to eat and their pre-meal blood sugar. This requires the person to perform basic arithmetic.

The pre-meal insulin dose is calculated by dividing the number of carbohydrates to be consumed by the number of carbohydrates covered by one unit of insulin (insulin-to-carbohydrate ratio). This dose is then adjusted based upon the pre-meal blood sugar reading (see correction factor below). Some insulin pumps can perform these calculations.

• Insulin-to-carbohydrate ratio — An insulin-to-carbohydrate ratio is determined by a dietitian or diabetes educator. This allows you to calculate the dose of rapid-acting insulin needed to cover a meal or snack.
  
  For example, if the insulin-to-carbohydrate ratio is 1 to 10, then you would give 1 unit of insulin for every 10 grams of carbohydrate consumed. If you ate a meal with 70 grams of carbohydrates, the dose of rapid-acting insulin would be 7 units. Most insulin pumps are able to give tenths of a unit, so that 78 grams of carbohydrate would require 7.8 units of insulin.
• Correction factor — The pre-meal insulin dose can also be adjusted based upon the pre-meal blood sugar level; this is called a correction factor. The correction factor can be determined by a dietitian or diabetes educator.
  
  For example, let's assume that the correction factor is 30. If the pre-meal blood sugar was 240 mg/dL and the goal BG was 120 mg/dL, take 240 minus 120 = 120. Then divide 120 by 30 = 4 extra units of insulin to correct the high blood sugar level.
  
  For patients whose blood sugar is measured in mmol/L, a different formula is used. Let's assume a correction factor of 2. If the pre-meal blood sugar was 14 mmol/L and the goal blood sugar was 6 mmol/L, take 14 minus 6 = 8. Then divide 8 by 2 = 4 extra units of insulin to correct the high blood sugar.

Exchange planning — With exchange planning, all foods are categorized as either a carbohydrate, meat or meat substitute, or fat. In this system, one serving of a carbohydrate (eg, 1 small apple) can be exchanged for any other carbohydrate (eg, 1/3 cup cooked pasta) because both servings contain about 15 grams of carbohydrate.

The exchange lists also identify foods that are good sources of fiber, and foods that have a high sodium content. A dietitian can determine how many servings of each group should be eaten at each meal and snack (table 2).

WHAT SHOULD I EAT?

While protein and fat do not affect blood glucose levels significantly, they do contribute to the number of calories consumed. Eating a consistent number of calories every day can help to maintain body weight. An individual's recommended calorie intake is discussed below. (See 'Recommended calorie intake' below.)

General recommendations — The American Diabetes Association recommends the following to help manage the ABCs (A1C, blood pressure and cholesterol) and promote good health:

• Less than 25 to 35 percent of calories per day should be from fat, and less than 7 percent of calories per day should be from saturated fat; there should be minimal trans fat. Saturated and trans fats are found in solid fats like butter, margarine, and shortening. People with diabetes are at increased risk for heart disease and stroke, and eating a diet low in saturated and trans fats and cholesterol diet can help to manage cholesterol levels and decrease these risks.
• Total cholesterol intake should be less than 200 mg per day. The main sources of cholesterol in the diet are foods such as organ meats, egg yolks, and whole milk.
• Between 15 and 20 percent of calories should be from protein, except in people with certain kidney problems (chronic kidney disease or CKD). People with CKD are sometimes advised to eat a low-protein diet. (See "Patient information: Chronic kidney disease".)
• A diet that is high in fiber (25 to 30 grams per day) may help to control blood sugar levels and AIC. (See "Patient information: High-fiber diet".)
• A diet that is low in sodium (less than 2300 mg per day) and that is high in fruits, vegetables, and low fat dairy products, is recommended and can help manage blood pressure. For people with diabetes and heart failure, a low sodium diet may reduce symptoms. (See "Patient information: Low sodium diet".)
• Artificial sweeteners do not affect blood sugar levels and may be consumed in moderation. The US Food and Drug Administration has approved five artificial sweeteners: aspartame (Equal, NutraSweet), saccharin (Sweet'N Low, Sweet Twin), acesulfame-K (Sunnet, Sweet One), neotame, and sucralose (Splenda).
  
  Sugar alcohols (sorbitol, xylitol, lactitol, mannitol, and maltitol) are often used to sweeten sugar-free candies and gum, and increase blood sugar levels slightly. When calculating the carbohydrate content of foods, one half of the sugar alcohol content should be counted in the total carbohydrate content of the food. Eating too much sugar alcohol at one time can cause cramping, gas, and diarrhea.
• Previously, people with diabetes were told to avoid all foods with added sugar. This is no longer necessary, although sugar should be eaten in moderation. If you take insulin, calculate your dose based upon the number of carbohydrates, which already includes the sugar content, as described above. (See 'Carbohydrate counting' above.)
• Products that are "sugar-free" or "fat-free" do not necessarily have a reduced number of calories or carbohydrates. Read the nutrition label carefully and compare it to other similar products that are not sugar- or fat-free to determine which has the best balance of serving size and number of calories carbohydrates, fat, and fiber.
  
  Some sugar-free foods, such as diet soda, sugar-free gelatin, and sugar-free gum, do not have a significant number of calories or carbohydrates, and are considered "free foods". Any food that has less than 20 calories and 5 grams of carbohydrate is considered a free food, meaning that there are not enough calories or carbohydrates to affect your weight or require additional insulin.

Recommended calorie intake — The number of calories needed to maintain weight depends upon your age, sex, height, weight, and activity level. In general:

• Men, active women — 15 calories/pound
• Most women, sedentary men, and adults over 55 years — 13 cal/lb
• Sedentary women, obese adults — 10 cal/lb
• Pregnant, lactating women — 15 to 17 cal/lb

To lose 1 to 2 pounds per week (a safe rate of weight loss), subtract 500 to 1000 calories from the total number of calories needed to maintain weight.
As an example, an overweight man who weighs 250 lbs would need to eat 2500 calories per day to maintain his weight. To lose weight, he should eat 1500 to 2000 calories per day. As weight is lost, his recommended calorie intake should be recalculated.

TYPE 1 DIABETES, DIET, AND WEIGHT

Your weight is a direct reflection of how much you eaten and how active you are. Eating a consistent number of calories every day can help to control blood sugar levels and maintain body weight.

Avoiding weight gain — Weight gain is a potential side effect of intensive insulin therapy in type 1 diabetes. To avoid weight gain, the following tips are recommended.

• Measure your weight on a regular basis (eg, once weekly). Weight gains of more than 2 to 3 pounds indicate a need to decrease what you eat or increase your activity. Do not wait until weight increases by 10 or more pounds to take action.
• As blood sugar control improves, it may be necessary to decrease your calorie intake by 250 to 300 calories to avoid weight gain.
• If blood sugar levels are frequently low at a particular time of day, talk to a healthcare provider about decreasing the insulin dose rather than adding a snack.

Exercise — Exercising regularly can help to lose weight and keep it off. The recommended amount of exercise is 30 minutes per day most days of the week. (See "Patient information: Exercise".)

People who take insulin should check their blood sugar level before and after exercising. If exercise is vigorous and prolonged (more than thirty minutes), check your blood sugar every fifteen minutes (if the exercise regimen is new and will be used again). Frequent monitoring can help to get a sense of what effect exercise has on your blood sugar level.
If your blood sugar becomes low during exercise, eat a snack according to the guidelines below. (See "Patient information: Hypoglycemia (low blood sugar) in diabetes mellitus".)

• If the blood glucose is 51 to 70 mg/dL (2.8 to 3.9 mmol/L), eat 10 to 15 grams of fast-acting carbohydrate (eg, 1/2 cup fruit juice, 6 to 8 hard candies, 3 to 4 glucose tablets).
• If the level is less than 50 mg/dL (2.7 mmol/L), eat 20 to 30 grams of fast-acting carbohydrates.

Retest after 15 minutes and repeat treatment if needed. If the next meal is more than an hour away, eat an additional 15 grams of carbohydrate and 1 ounce of protein (for example, crackers with cheese or one-half of a sandwich with peanut butter). Try not to eat too much because this can raise blood sugar levels above the target level and lead to weight gain over the long term.

Adjusting insulin dose for exercise — It may be possible to reduce the insulin dose before exercising to avoid developing low blood glucose. A physician, diabetes educator, or exercise physiologist can help to determine the best way to adjust your insulin dose before, during, and after exercising. People who take oral diabetes medications usually do not need to adjust the dose of these medications for exercise.

TYPE 1 DIABETES AND ALCOHOL

Drinking a moderate amount of alcohol (up to 1 serving per day for women, up to 2 servings per day for men) with food does not affect blood sugar levels significantly. Alcohol may cause a slight rise in blood sugar, followed hours later by a decrease in the blood glucose level. As a result, it is important to monitor blood sugar response to alcohol to determine if any changes in insulin doses are needed.
Mixers, such as fruit juice or regular cola, can increase blood sugar levels and increase the number of calories consumed in a day. If mixers are consumed, a dose of insulin may be needed.

TYPE 1 DIABETES AND EATING DISORDERS

Eating disorders are relatively common in people with diabetes, especially in female adolescents and young adults with type 1 diabetes. This may be due, in part, to the difficulty of balancing food intake, exercise, and blood sugar levels, which sometimes leads to weight gain, especially in people who use intensive insulin therapy or an insulin pump.
People with eating disorders and diabetes often use unhealthy strategies to control their weight, including:

• Giving less insulin than required (or no insulin)
• Severely restricting the amount of food eaten
• Eating a large amount of food at one time (binge eating). After binging, some people vomit (purge), use laxatives inappropriately, or exercise excessively.

Eating disorders can cause serious complications in anyone, although the consequences for people with diabetes can be especially severe. The kidneys and retinas (in the eyes) are at high risk of becoming damaged as a result of eating disorders, especially if blood sugar levels are chronically high due to underdosing of insulin. Missing or underdosing insulin, even occasionally, is harmful.
If you have concerns about your body weight, size, or shape, you should speak honestly with your healthcare provider. The provider can help to make a plan that includes a reasonable diet, exercise, and if needed, counseling regarding body image.