Patient education: Type 1 diabetes and diet (Beyond the Basics)

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 reach your glycated hemoglobin (A1C) goals and achieve blood sugar targets, it is important 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, diabetes educator, and/or other diabetes care provider, it is possible to eat well and control diabetes.

This topic discusses how to manage your diet if you have type 1 diabetes. The role of diet and activity in managing blood pressure and cholesterol is reviewed separately. (See "Patient education: High blood pressure, diet, and weight (Beyond the Basics)" and "Patient education: High cholesterol and lipids (Beyond the Basics)".)

WHY IS DIET IMPORTANT? — Many factors affect overall blood sugar levels. These include how much and what you eat, how frequently you check your blood sugar, whether you routinely use continuous glucose monitoring (CGM), your physical activity level, and the accuracy and consistency of insulin dosing. Even small changes in behaviors or insulin dosing can affect blood sugar management.

Eating a consistent amount of food every day and taking insulin as directed can greatly improve blood sugar levels. It can also lower your risk of diabetes-related complications, such as coronary artery disease, kidney and eye disease, and nerve damage. In addition, these measures impact body weight management.

A dietitian can help you create a food plan that is tailored to your medical needs, lifestyle, and personal preferences.

TYPE 1 DIABETES AND MEAL TIMING — People who use an insulin pump or take insulin doses tailored to each meal have flexibility in the timing of meals. With these regimens, skipping or delaying a meal does not usually increase the risk of low blood sugar. However, consistently eating at the same times every day is important for some people, especially those who take the longer-acting insulin NPH or those who take about the same amount of insulin at the same time every day (called a "fixed regimen"). If a meal is skipped or delayed, people who use these insulin regimens are at risk for developing low blood glucose.

High-fat or high-protein meals — Foods or meals that are high in fat (eg, pizza) may be eaten occasionally, although blood sugar levels should be monitored more closely. High-fat, high-protein meals are broken down more slowly than lower-fat, lower-protein meals. When using rapid-acting insulin (eg, Humalog, Novolog) before a high-fat, high-protein meal, the blood sugar level may rise and stay high for several hours after the meal, or it may fall shortly after the meal and then rise hours later. People who consume meals containing more protein or fat than usual may need to make meal-time insulin dose adjustments to manage the delayed and/or prolonged rise in blood sugar. Your provider can help determine the best strategy for these adjustments.

People who use an insulin pump can use an extended insulin delivery regimen to better manage blood sugar levels after eating a high-fat or high-protein meal.

TYPE 1 DIABETES AND CARBOHYDRATE CONSISTENCY — Carbohydrates or "carbs" are the main energy source in most diets and include starches, starchy vegetables (eg, corn, potatoes, peas, and legumes), fruits, dairy products, and sugars. Most meats and fats do not contain any carbohydrates.

Carbohydrates have the greatest direct impact on blood sugar levels. Eating a consistent amount of carbohydrates at each meal can help to regulate blood sugar levels, especially if you take about the same amount of insulin at the same time every day (fixed regimen).

There are several ways to calculate the 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. Most people with diabetes report a moderate intake of carbohydrate (44 to 46 percent of total calories).

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).

You can figure out the number of carbohydrates in a particular food by reading the nutrition label, consulting a reference book or website, using a smartphone app, or using the "Exchange system" (see 'Exchange planning' below). Restaurants usually have this information available upon request.

It is important to note the serving size and grams of fiber when calculating carbohydrates. Eating more than one serving of any food will increase the number of calories and carbohydrates consumed and the dose of insulin needed to cover the meal. For example, some pre-packaged snacks contain two or more servings. To calculate the carbohydrate content of the entire package, multiply the number of servings by the number of carbohydrates per serving.

When a serving of food has more than 5 grams of fiber, the number of grams of fiber should be subtracted from the number of grams of carbohydrates to calculate the insulin dose (figure 1).

Exchange planning — With exchange planning, all foods are categorized as either a carbohydrate, meat or meat substitute, or fat. In the exchange system, one serving of a carbohydrate (eg, one small apple) can be exchanged for any other carbohydrate (eg, 1/3 cup cooked pasta) because both servings contain approximately 15 grams of carbohydrate. You can easily determine the carbohydrate content of your meals and snacks using the Exchange system (table 2).

A dietitian can help you determine how many servings of each food group should be eaten at each meal and snack (table 2) and the ideal carbohydrate content of each meal and snack.

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). Most insulin pumps can perform these calculations.

●Insulin-to-carbohydrate ratio – An insulin-to-carbohydrate ratio is determined by a health care provider, dietitian, or diabetes educator. This ratio 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 or insulin sensitivity factor. The correction factor can be determined by a health care provider, dietitian, or diabetes educator.

For example, let's assume that the correction factor is 30. This means that each unit of insulin should lower blood sugar by 30 mg/dL. If the pre-meal blood sugar was 240 mg/dL and the goal blood sugar 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 people whose blood sugar is measured in mmol/L, a different formula is used. Let's assume a correction factor of 2. This means that every unit of insulin should lower blood sugar by 2 mmol/L. 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.

WHAT SHOULD I EAT? — While protein and fat in small to moderate amounts 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. Recommended calorie intake is discussed more below. (See 'Recommended calorie intake' below.)

General recommendations — The American Diabetes Association (ADA) nutritional guidelines do not give specific total dietary compositional targets except for the following recommendations, which are in large part similar to the recommendations for the general population (see "Healthy diet in adults"):

●A diet that includes carbohydrates from fruits, vegetables, whole grains, legumes, and low-fat milk is encouraged. People with diabetes are advised to avoid sugar-sweetened beverages (including fruit juice).

The ideal amount of carbohydrate intake is uncertain. However, monitoring carbohydrate intake (using basic or advanced carbohydrate counting) is important for people with diabetes. This is because carbohydrate intake directly determines postprandial (after meal) blood sugar, and appropriate insulin adjustment for consumed quantities of carbohydrate is one of the most important factors that can improve blood sugar management.

When considered in addition to total carbohydrates, meals with low "glycemic index" and "glycemic load" may provide a modest additional benefit for regulating blood sugar levels. Glycemic index and glycemic load refer to how much and how quickly a food raises your blood sugar level after eating it.

●A variety of eating patterns (low fat, low carbohydrate, Mediterranean, vegetarian) are acceptable.

●The quality and quantity of dietary fat are both important. Saturated fat and trans fat contribute to coronary heart disease (CHD), while monounsaturated and polyunsaturated fats are relatively protective. People with diabetes are at increased risk for heart disease and stroke, and eating a diet low in saturated fat, trans fat, and cholesterol can help to reduce cholesterol levels and decrease these risks.

Saturated fats (eg, in meats, cheese, ice cream) can be replaced with monounsaturated and polyunsaturated fats (eg, in fish, olive oil, nuts). Trans fat consumption should be kept as low as possible. Trans fats are banned from processed foods in the United States. Although very small amounts of trans fats are naturally present in meats, poultry and dairy products, the amount is too small for concern.

●The role of dietary protein restriction is uncertain, particularly in view of the challenges for people already restricting the saturated fat and simple carbohydrate content of their diets. Furthermore, it is uncertain if a low-protein diet is significantly additive to other measures aimed at reducing cardiovascular risk and preserving kidney function, such as medications and optimal management of blood pressure and blood glucose. Thus, protein intake goals should be individualized.

The usual daily intake of protein is typically 15 to 20 percent of total caloric intake. An automatic reduction of dietary protein intake below usual protein intake in people who develop diabetic kidney disease is not recommended. Those with kidney disease should aim to maintain a dietary protein intake at the recommended daily allowance of 0.8 g/kg body weight per day. People with type 1 diabetes should be encouraged to substitute lean meats, fish, eggs, beans, peas, soy products, and nuts and seeds for red meat. (See "Patient education: Chronic kidney disease (Beyond the Basics)".)

●A diet that is high in fiber (25 to 30 grams per day) may help to regulate blood sugar levels and achieve glycated hemoglobin (A1C) targets (table 3). (See "Patient education: High-fiber diet (Beyond the Basics)".)

●A diet that is low in sodium (less than 2300 mg per day) and 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 (low salt) diet may reduce symptoms. Restriction of sodium to less than 1500 mg per day is not generally recommended. (See "Patient education: Low-sodium diet (Beyond the Basics)".)

●Artificial sweeteners do not affect blood sugar levels and may be consumed in moderation. For those who consume sugar-sweetened beverages regularly, a beverage containing artificial sweeteners can be a good short-term replacement strategy. However, people are encouraged to decrease both sweetened and artificially sweetened beverages, with an emphasis on increasing water intake.

The US Food and Drug Administration (FDA) has tested and approved five artificial sweeteners: aspartame (Equal, NutraSweet), saccharin (Sweet'N Low, Sugar Twin), acesulfame-K (Sunett, Sweet One), neotame, and sucralose (Splenda). Stevia (sometimes called rebaudioside A or rebiana) comes from the stevia plant and is now generally recognized as safe by the FDA as a food additive and tabletop sweetener. When something is generally recognized as safe by the FDA, it means that experts have agreed that it is safe for use by the public in appropriate amounts.

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 to be sure that consumption of foods with added sugar do not displace healthier food choices. 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.

The ADA has a website called Diabetes Food Hub (www.diabetesfoodhub.org) that many people find useful. The site has tools to help you manage your diabetes, including nutrition information and customizable recipes you can use in meal planning.

Recommended calorie intake — The number of calories needed to maintain weight depends upon your age, sex, height, weight, and activity level. In general, the following number of daily calories per pound of body weight will result in body weight maintenance:

●Men, active women – 15 calories/lb

●Most women, sedentary men, and adults over 55 years – 13 cal/lb

●Sedentary women, adults with obesity – 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 daily calories needed to maintain weight.

As an example, a man with obesity 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 determined in part by how much you have eaten and how active you are. Eating a consistent number of calories every day can help to regulate 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 gain of more than 2 to 3 pounds indicates 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 levels improve, 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 or you regularly are eating solely to avoid a low blood sugar (rather than eating for hunger), talk to a health care provider about decreasing the insulin dose.

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, or 150 minutes or more of aerobic exercise spread over three or more days per week. It is important to avoid having more than two consecutive days without exercise. Even gentle forms of activity, like walking, are good for your health. (See "Patient education: Exercise (Beyond the Basics)".)

People who take insulin should check their blood sugar level before and after exercising. If exercise is vigorous and prolonged (more than 30 minutes), check your blood sugar every 15 minutes. Frequent monitoring is particularly important if the exercise regimen is new and 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 education: Hypoglycemia (low blood glucose) in people with diabetes (Beyond the Basics)"):

●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, six to eight hard candies, three to four 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, dietitian, or exercise physiologist can help to determine the best way to adjust your insulin dose before, during, and after exercising.

TYPE 1 DIABETES AND ALCOHOL — Drinking a moderate amount of alcohol (up to one serving per day for women, up to two servings per day for men) with food does not typically 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 type 1 diabetes, especially in female teens and young adults. 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 health care provider. They can provide support and help to make a plan that includes a reasonable diet, exercise, and, if needed, counseling regarding body image.

WHERE TO GET MORE INFORMATION — Your health care provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our website (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Type 1 diabetes (The Basics)
Patient education: Diabetes and diet (The Basics)
Patient education: My child has diabetes: How will we manage? (The Basics)
Patient education: Managing blood sugar in children with diabetes (The Basics)
Patient education: Managing diabetes in school (The Basics)
Patient education: Checking your child's blood sugar level (The Basics)
Patient education: Carb counting for children with diabetes (The Basics)
Patient education: Preparing for pregnancy when you have diabetes (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: High blood pressure, diet, and weight (Beyond the Basics)
Patient education: High cholesterol and lipids (Beyond the Basics)
Patient education: Chronic kidney disease (Beyond the Basics)
Patient education: High-fiber diet (Beyond the Basics)
Patient education: Low-sodium diet (Beyond the Basics)
Patient education: Exercise (Beyond the Basics)
Patient education: Hypoglycemia (low blood glucose) in people with diabetes (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Initial management of hyperglycemia in adults with type 2 diabetes mellitus
Nutritional considerations in type 1 diabetes mellitus
Nutritional considerations in type 2 diabetes mellitus

The following organizations also provide reliable health information.

●National Library of Medicine

(www.nlm.nih.gov/medlineplus/healthtopics.html)

●National Institute of Diabetes & Digestive & Kidney Diseases

(www.niddk.nih.gov)

●American Diabetes Association (ADA)

(www.diabetes.org)

●The Endocrine Society

(www.endo-society.org)

●Hormone Health Network

(www.hormone.org/diseases-and-conditions/diabetes)

The following reference books are a good source of information regarding diabetes and diet and carbohydrate counting:

●The Doctor's Pocket Calorie, Fat, and Carb Counter, Allan Borushek, also available for download to personal digital assistant at www.calorieking.com

●Practical Carbohydrate Counting, Hope Warshaw and Karmen Kulkarni

●Smart Pumping: A Practical Approach to Mastering the Insulin Pump, Howard Wolpert

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