Glucose is the sugar that circulates in your blood and serves as the body’s main source of energy. The digestion and breakdown of carbohydrate-containing foods into their simplest form produces glucose. A person’s blood glucose goes up after she eats, but certain foods have more of an impact on glucose levels than others. Medications, stress, illness and lack of exercise can also affect glucose levels in those with diabetes or insulin resistance.
Carbohydrates Raise Glucose
Carbohydrates are found in all foods that contain starch, fiber or sugar. Each of these will cause an increase in blood glucose levels when digested, but the rate and level of increase can vary with each type of carbohydrate. Starch and fiber-rich foods are also called complex carbs, and in general, they raise blood sugar more slowly. Sugar-rich foods, or simple carbs, will raise blood glucose more quickly and sometimes much higher.
Starch Is a Slow Carb
Starch can come from vegetables, legumes or grains. Starchy foods that are high in fiber raise blood glucose more slowly because they take longer to digest and break down. High-fiber foods also cause less of an increase in blood glucose because fiber is the part of plants that is indigestible, so it doesn’t contribute any glucose. The American Diabetes Association recommends choosing nutritious, high-fiber starches like most vegetables; legumes, including kidney beans, lentils or chickpeas; and whole grains like oats, brown rice or whole-wheat breads and cereals. Some starch foods are quicker for the body to digest, and as a result they raise glucose more quickly. These include starchy vegetables like white potatoes, corn or peas, and refined grains like white bread, rice or pasta.
The Sugar Spike
Sugar is another type of carbohydrate that raises blood glucose levels quickly. Some foods like fruit or milk contain natural sugar, and other foods like desserts or candy contain added sugars. The sugar in these foods is sometimes called simple sugar, or fast-acting carbohydrate, because it’s easily digested by the body and, as a result, increases blood glucose quickly. Foods that are high in simple sugar include any type of fresh or dried fruit or fruit juice, milk or yogurt, and any sweets or baked goods. Desserts and sweets with lots of added sugar can increase blood glucose very quickly. For individuals with diabetes, such sweet foods can sometimes cause blood glucose levels to skyrocket.
Medications or Hormones May Also Be to Blame
Sometimes glucose can increase because of hormonal changes, as in the case of gestational diabetes during pregnancy, or from medications, such as certain corticosteroids or psychiatric medications. For individuals with diabetes or insulin resistance, blood glucose often increases if medications are not taken at the correct times as prescribed. Stress, illness or infection, inadequate exercise or decreased physical activity can also spike blood sugar. It's important to eat a balanced diet with healthy carbs, exercise and have your blood glucose checked regularly. According to the National Diabetes Education Program, 7 million Americans are unaware that they have diabetes.
- Harvard School of Public Health: Carbohydrates and Blood Sugar
- American Diabetes Association: Types of Carbohydrates
- Joslin Diabetes Center: How Does Fiber Affect Glucose Levels?
- American Diabetes Association: Grains and Starchy Vegetables
- Cleveland Clinic: Hyperglycemia
- National Diabetes Education Program: The Facts About Diabetes: A Leading Cause of Death in the U.S.