Carbohydrates and Diabetes

Carbohydrates and Diabetes


Carbohydrates, along with proteins and fats, are one of the three main food nutrients. They are the sugars and starches in foods that provide the main fuel for the body’s energy needs. They are also the substances that most affect a person’s glucose (blood sugar) levels.

People with diabetes either cannot properly use or cannot produce insulin, a body hormone that prevents glucose levels from going too high or low. As a result, diabetic individuals must pay close attention to the amount and type of carbohydrates they consume as a way of keeping glucose in check.

About 90 percent of the carbohydrates a person consumes show up in the blood as glucose within two hours of being digested. Eating too many carbohydrates can cause hyperglycemia, but not eating enough can cause hypoglycemia or trigger ketosis, a potentially troublesome state for diabetic patients in which the body burns fats instead of glucose for energy.

There are two primary kinds of carbohydrates:

  • Complex carbohydrates (starches). These include grain products, potatoes and vegetables that provide essential nutrition in the form of vitamins, minerals and fiber.
  • Simple carbohydrates (sugars). These are found in fruit, milk products and sweets. Some simple carbohydrates – including fruits, milk and yogurt – contain valuable vitamins and minerals important to health. Other simple carbohydrates provide calories but little or no nutritional value. They can lead to undesired weight gain and obesity, a major risk factor for diabetes.

Different types of carbohydrates break down into glucose at various rates. Some peak rapidly and cause glucose levels to surge, and others are slower acting and cause a more gradual rise in blood glucose levels. A measurement system known as the glycemic index can help people with diabetes understand how various foods affect glucose levels. Methods including diabetic food exchange and carb counting can help patients track their consumption of carbohydrates.

About carbohydrates & diabetes

Carbohydrates are the sugars and starches that provide the fuel for the human body. These substances are found in many foods and are broken down during digestion into a simple sugar called glucose (blood sugar). Once glucose is absorbed into the bloodstream, a hormone in the body called insulin moves it into the cells, where it is converted to energy.

Carbohydrates also are the source of a substance called glycogen. This fuel reserve is stored in the liver, fat and muscles and can be broken down into glucose when the body does not receive enough carbohydrates from outside food sources.

People with diabetes either do not produce insulin (type 1 diabetes) or cannot properly use the insulin they do produce (type 2 diabetes). As a result, the level of glucose in the blood is prone to quickly rising too high (hyperglycemia). Conditions including insufficient consumption of carbohydrates can also cause patients’ blood glucose to fall too low (hypoglycemia).

Severe episodes of acute hyperglycemia or hypoglycemia can result in a diabetic coma, and chronic hyperglycemia can cause many complications ranging from heart conditions to diabetic retinopathy. Diabetic individuals can help prevent glucose irregularities by controlling the amount and type of carbohydrates they consume.

The body gains energy by breaking down three major classes of foods. These groups, known as macronutrients, are:

  • Carbohydrates.
  • Fats. Fats are a major source of energy for the body, with each gram providing nine calories. Types include saturated, monounsaturated and polyunsaturated. Saturated fats are the so-called “bad” fats found in animal and dairy products. Harmful, artery-clogging artificial trans fats are unsaturated fats processed to act like saturated fats.
  • Proteins. Proteins provide energy as a last resort when other energy sources are depleted. The main job of proteins is to build and repair cells.  

In addition, many alcoholic beverages including beer, wine and cocktails contain carbohydrates.  If a physician approves the use of alcohol, these carbs must be included in meal planning.

Carbohydrates are broken down and converted to glucose, which is the fuel for the body’s activities. Such activities include autonomic functions such as breathing, digestion and heartbeat, and forms of exertion such as running and lifting. In addition, glucose is normally the sole fuel source for the brain.

Carbohydrates are divided into two classes:

  • Complex carbohydrates (starches). These include whole-grain breads and cereals, legumes and starchy vegetables that provide nutrition in the form of vitamins, minerals and fiber. Fiber, in carbohydrates such as oatmeal, protects starchy carbohydrates from digestive enzymes. This slows the absorption of glucose from the small intestine into the bloodstream, which can be beneficial to diabetic individuals trying to control their blood glucose levels. Fiber can also help control cholesterol. However, people who have gastroparesis, a type of autonomic neuropathy that delays digestion, may need to limit fiber.
  • Simple carbohydrates (sugar). These are found in milk products, fruit, candy, soda and other sweets. Fruit and milk products are important sources of valuable nutrients, vitamins and minerals. Candy, soda and sweets provide few or no nutrients. Though these carbohydrates help provide fuel for energy, they are “empty calories” with no nutritional value. An excess intake of simple carbohydrates can lead to undesired weight gain and obesity, a major risk factor for several forms of diabetes.

Each type of carbohydrate contains four calories per gram. Gram for gram, simple and complex carbohydrates eventually add the same amount of glucose to the bloodstream. However, complex carbohydrates are broken down into glucose more slowly than simple carbohydrates. Complex carbohydrates provide important sources of essential nutrients for a good diet. People with diabetes are usually advised to favor the slower-acting complex carbohydrates, as they lessen the likelihood of rapid rises in blood glucose.

Some carbohydrates have been highly refined (for example, white bread, cake and cookies), and may be considered neither simple carbohydrates nor complex carbohydrates. For example, grains can be classified as whole grains or refined grains.

A grain is made up of:

  • Bran (outer shell with fiber, B vitamins and minerals)
  • Germ (next layer, with nutrients such as fiber, essential fatty acids and vitamins)
  • Endosperm (center of the grain, containing the starch)

Whole grains are complex carbohydrates that include all three elements, but refined grains contain only the endosperm, or starch. Whole grains are therefore far more nutritious than refined grains, which provide energy but few nutrients.

The further a food is away from its natural state, the less nutritious it is. Healthy carbohydrate choices in appropriate amounts are vital for nutrition.

Studies have shown that controlled-carbohydrate diets can improve control of glucose and blood pressure and may decrease insulin resistance. However, diets very low in carbs can cause problems including headaches, constipation, muscle cramps and fatigue.

Eating fewer than 130 grams of carbohydrates a day can cause ketosis, according to the National Institutes of Health (NIH). Ketosis is a state in which the body, deprived of carbohydrates to use for fuel, burns fats instead. Though ketosis promotes weight loss, it can also lead to gout and kidney stones and may be especially problematic for diabetic patients, people with kidney disease (e.g., diabetic nephropathy) and pregnant women, according to the NIH.

A dangerous condition called diabetic ketoacidosis (DKA) involves severe hyperglycemia and ketosis. Dietary ketosis may contribute to DKA, but DKA is typically triggered by causes such as a missed dose of insulin or a severe illness.

Some proponents assert that low-carb diets can help prevent type 2 diabetes, but all individuals interested in trying such plans, including those with prediabetes, a family history of diabetes or other risk factors for diabetes, are advised to consult their physician first.

Diabetic patients are advised to establish a meal plan with the help of their physician and a registered dietitian. They should also ask their physician how often to perform glucose monitoring and ketone tests. During illness, people with diabetes typically need to eat their usual amount of carbohydrates. A factor that can affect consumption of carbs is exercise.

Types and differences of carbohydrates

Carbohydrates are an essential part of the human diet. They provide most of the energy for the body, as well as many vitamins and nutrients. The American Diabetes Association (ADA) recommends that carbohydrates make up 50 percent to 60 percent of daily calorie consumption for most people, though instruction from an individual’s physician, registered dietitian or certified diabetes educator may vary.

The majority of those calories should be from complex carbohydrates. Increased dietary fiber benefits most people, though this may cause problems for patients with gastroparesis, a form of autonomic neuropathy that affects digestion.

There are two major types of carbohydrates: complex (also known as starches) and simple (also known as sugars). Simple sugars can be naturally occurring or added. Sources of carbohydrates include:

Sources of Complex Carbohydrates

Black-eyed peas
Kidney beans
Lima beans
Pinto beans
Split peas
Edible seeds

*Also in grain products such as whole–wheat bread, crackers or pasta.

Sources of Simple Carbohydrates (Natural)

Fructose (fruit sugar)Lactose (milk sugar)
Fruit juice and fruits such as apples, oranges, pineapples, etc.Dairy products such as milk and yogurt

Sources of Simple Carbohydrate (Added)

Beet sugar
Brown sugar
Cane sugar
Confectioner’s sugar
High-fructose corn syrup
Maple syrup
Powdered sugar
Raw sugar
Sugar cane syrup
Table sugar (sucrose)
Turbinado (a sugar cane extract)

Simple sugars are also found in:

  • Candy
  • Cookies
  • Pastries
  • Carbonated beverages
  • Many processed foods, such as ketchup, salad dressings, canned chili and frozen dinners

Carbohydrates are scientifically classified into the following categories:

  • Monosaccharides. The simplest sugars, of which glucose is the primary example.
  • Disaccharides. Sugar made of two monosaccharides. Examples include lactose and sucrose.
  • Trisaccharides. Sugar made of three monosaccharides.
  • Polysaccharides. Sugar composed of a number of monosaccharides joined together by glycosidic bonds (the dehydration reaction between the hydroxide on the right edge of one sugar to the hydroxide on the left edge of the other sugar). Examples include starch and cellulose.
  • Heterosaccharides. A glycoside in which a sugar group is attached to a nonsugar group.

Certain foods contain few or no carbohydrates. They include proteins and fats such as:

  • Meat, poultry and fish
  • Eggs
  • Cheese
  • Butter
  • Oils

Nuts such as almonds, seeds such as sunflower seeds and nut-like foods such as cashews and peanuts provide fats, carbohydrates and proteins in varying amounts.

Dietary exchanges and carbohydrate counting

Carbohydrates have a major effect on a person’s glucose (blood sugar). It is crucial that diabetic individuals keep track of their carbohydrate consumption as a means of avoiding high glucose (hyperglycemia) or low glucose (hypoglycemia).

Most of the health complications associated with diabetes, such as kidney disease (diabetic nephropathy), heart conditions and diabetic coma, are related to glucose problems. Several dietary techniques can improve control of glucose, including:

  • Dietary exchange system. A method of categorizing foods into groups that share similar carbohydrate, calorie, protein and fat content. Established by the American Diabetes Association and the American Dietetic Association, it consists of three groups:
    • Carbohydrate group
    • Meat and meat substitutes group
    • Fat group

      The carbohydrate group contains foods in the following subgroups:
    • Starches
    • Fruits
    • Milk
    • Vegetables
    • Other carbohydrates (such as table sugar, yogurt, fruit snacks and jelly)

      The American Diabetes Association recommends that carbohydrates should make up 50 percent to 60 percent of daily calorie consumption for most individuals.

  • Carbohydrate counting. Also known as “carb counting,” this is a method in which people with diabetes carefully count the number of carbohydrates they consume to make sure they do not exceed their recommended levels. Various products can help patients track carbohydrate consumption.

    To do this accurately, individuals need to determine how many carbohydrates are in a single serving of the food they are eating. “Nutrition facts” labels are good sources for this information. Patients should remember that a single serving size as displayed on these lists is based on weight, and not just how much food a person eats in a single meal. Once patients have this information, they need to weigh and measure the food to calculate carbohydrate intake based on serving size.

    There are five basic steps in carbohydrate counting:
    • Step 1: Carbohydrate count goals. These goals will depend on the type of antidiabetic agents or insulin used. There are two considerations:
      • Consistency in the amount of carbohydrate consumed at snacks and meals. If insulin is used, or an antidiabetic agent that increases the amount of insulin produced by the body, the same amount of carbohydrate needs to be consumed at meals and snacks each day to maintain consistent levels of blood glucose.
      • Maximum amounts of carbohydrates to be consumed at each snack and meal. The kind of medication used by a diabetic individual is an important factor in this amount. Patients who use rapid-acting insulin can adjust the amount of insulin taken to match the amount of carbohydrate eaten.
  • Step 2: Know how much is consumed. A food and glucose record should be kept to record meal and snack information on the effects of food on glucose.
  • Step 3: Knowledge. Know what foods contain carbohydrates, the type of carbohydrate, and the amount that should be consumed at meals and snacks. For example, one slice of whole-grain bread contains the same amount of carbohydrate as three cups of raw vegetables or one tablespoon of sugar.
  • Step 4: Food labels. The nutrition information on food labels indicates the serving size and amount of carbohydrate and other nutrients in each serving. Reading food labels provides important information for managing food intake.
  • Step 5: Meal planning. There are many sources of diabetic recipes. People with diabetes should work with a registered dietitian to develop a meal plan that fits the lifestyle, culture, personal preferences and activity level.

Another method that can be used, the glycemic index, accounts for how the various carbohydrates affect glucose. Other diet tools include the diabetes food pyramid and the “rate your plate” system.

Questions for your doctor about carbohydrates

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about carbohydrates:

  1. How many carbs should I consume a day?
  2. What factors affect the amount of carbohydrates I need?
  3. Which types of carbs are better for me?
  4. What effects can sugar have on me?
  5. How can fiber benefit me? If I have gastroparesis, do I need to limit or avoid fiber?
  6. How do carbohydrates affect my glucose levels?
  7. Can eating carbs affect how I take insulin or other medications?
  8. Does illness affect the amount of carbs I need?
  9. Do I need more carbs when I exercise?
  10. Can you refer me to a registered dietitian to help with my diet?
  11. If I have prediabetes or a family history of type 2 diabetes, can I reduce my risk of diabetes by restricting carbs? What is the minimum daily amount I can safely eat?
  12. If I’m restricting carbs and develop ketosis, can this be dangerous for me? Can it lead to ketoacidosis?
Scroll to Top