Blood glucose is the term for glucose --- a dietary sugar --- in the bloodstream. When you eat glucose-containing foods, your intestine absorbs the glucose into the bloodstream. This makes the glucose available to your body cells, helping to provide for their nutritional needs. Keeping your blood sugar stable contributes to good health.
Glucose Chemistry
Glucose is an important nutrient molecule. Your body cells use it to provide for their energy needs, and the brain in particular depends upon a constant supply of glucose. As such, your body works hard to maintain a relatively constant level of glucose in the bloodstream. This quantity of glucose, called blood glucose or blood sugar, increases when you consume glucose-containing foods and decreases as your cells use glucose.
Raising Blood Glucose
When you eat glucose-containing foods, including foods that have sugar or starch in them, your digestive tract breaks the food down into its chemical constituents. You then absorb those nutritional building blocks, including glucose, into the bloodstream. This raises your blood sugar level. It's not healthy for your blood sugar to get too high. Excess blood sugar is called hyperglycemia; it can lead to tissue and organ damage.
Insulin
To help prevent blood sugar from getting too high after a meal that includes sources of dietary glucose, your pancreas releases the hormone insulin. Insulin serves as a signal to body cells to take up glucose from the bloodstream. Ideally the pancreas releases only enough insulin to signal cells to take up glucose in small amounts, reducing blood glucose to normal levels.
Glucose Rollercoaster
If you eat a large quantity of sugar or starch --- particularly if there are no digestion-slowing components of food such as fiber or protein in your meal --- you absorb glucose quickly. This causes your blood sugar to increase rapidly, which causes the pancreas to over-release insulin. In response, cells take up far too much insulin for their energy needs. Your blood sugar drops, leaving you fatigued and hungry, while cells convert glucose to fat for storage.
Diabetes
Two related but distinct metabolic disorders result from an inability to regulate blood sugar in response to dietary sugar intake --- type 1 and type 2 diabetes. In type 1 diabetes, patients can't produce insulin and must use injected insulin for cells to take up blood sugar. In type 2 diabetes, cells can't respond to insulin. These patients must control blood sugar by controlling diet and avoiding meals high in added sugars and carbohydrates.
References
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "Anatomy and Physiology"; Gary Thibodeau, Ph.D.; 2007
