Understanding Carbohydrates

Carbohydrates are made up of chains of sugar molecules and contain roughly equal amounts of carbon, hydrogen and oxygen. About 90 percent of the carbohydrates a person consumes show up in the blood as glucose within two hours of being digested. The more carbohydrates people consume, the higher their glucose levels rise.

The hormone insulin moves some of this glucose from the blood into the cells, where it is broken down and turned into energy for the body. Excess glucose is stored in the liver, muscles and fat cells as glycogen. This can be broken down into glucose later when needed by the body.

There are two primary kinds of carbohydrates:

  • Complex carbohydrates (starches). These include whole–grain breads, other 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, candy, soda and other sweets. Some simple carbohydrates – including fruits, milk and yogurt – contain valuable vitamins and minerals important to health. Other simple carbohydrates, such as candy and soda, help provide fuel for energy but are “empty calories” with no nutritional value and can lead to undesired weight gain.

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 helps people with diabetes understand how various foods effect glucose levels.

About Carbohydrates

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. 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 substance 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. To keep this hyperglycemia from occurring, diabetic individuals must keep a close watch on 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. There are three sources of fats – saturated, monounsaturated and polyunsaturated. Saturated fats are the so–called “bad” fats found in animal and dairy products.
  • 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.

Carbohydrates are broken down and converted to glucose, which is the fuel for body activities. Such activities include relatively simple tasks such as breathing and more demanding activities such as heavy lifting, running and other forms of exertion. In addition, glucose is 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.

  • 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.

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 healthy diet. People with diabetes usually try to eat the slower–acting complex carbohydrates, as they lessen the likelihood of rapid rises in blood glucose levels.

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.

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 should make up 50 percent to 60 percent of daily calorie consumption for most individuals. The majority of these calories should be from complex carbohydrates. According to the ADA, any increase in dietary fiber is beneficial.

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, pineapple, etc.

Dairy products such as milk, yogurt, cheese, etc.

Sources of simple carbohydrates (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)

Simple sugars are also found in:

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

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 non sugar group.

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

  • Meat
  • Fish
  • Eggs
  • Oils
  • Cheese
  • Butter

Dietary Exchanges and Carbohydrate Counting

Carbohydrates have a major impact on a person’s glucose (blood sugar) levels. For this reason, it is crucial that diabetic individuals keep close track of their carbohydrate consumption as a means of avoiding blood glucose levels from rising too high.

Most of the health complications associated with diabetes – including high blood pressure and unhealthy cholesterol levels – are related to high blood glucose (hyperglycemia). Prevention of hyperglycemia can be accomplished through a pair of techniques:

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:

  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 consistency in blood glucose levels.
    • 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.
  1. Know how much is consumed. A food and blood glucose record should be kept to record meal and snack information on the effects of food on blood glucose.

  2. 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.

  3. 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.

  4. Meal planning. All people with diabetes should work with a dietician to develop a personal meal plan that fits the lifestyle, culture, personal preferences and activity level

Before changing your diet, please see our diabetic educator/dietician at the Diabetes and Lipid Clinic of Alaska.

The information on this Web page is provided for educational purposes. You understand and agree that this information is not intended to be, and should not be used as, a substitute for medical treatment by a health care professional. You agree that Diabetes and Lipid Clinic of Alaska is not making a diagnosis of your condition or a recommendation about the course of treatment for your particular circumstances through the use of this Web page. You agree to be solely responsible for your use of information contained on this Web page

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