Glucose Metabolism
Glucose is the primary energy source for our body’s organ systems. After eating carbohydrates, glucose enters the bloodstream, causing blood sugar levels to rise. A peptide hormone called insulin is released from the pancreas, allowing for the movement of glucose into our cells to make energy. Glucose is stored in our cells as a molecule called glycogen, which can be broken down when our body requires sugar. In this case, glucagon, the opposite of insulin, stimulates the breakdown of glycogen to release glucose into the bloodstream. With the proper functioning of insulin and glucagon, our body maintains a balanced state. Without glucose, our body needs another source of energy. One diet that has gained popularity is the ketogenic diet, a diet low in carbohydrates and high in fat. On the ketogenic diet, your body runs on ketone bodies, the alternative source of energy the liver produces from fat. Most organs and tissues use ketone bodies for energy, including the brain, however, the brain requires a minimum glucose requirement to function.
Blood Glucose Analysis
There are various methods to check blood glucose levels to help screen for diabetes:
A1C Test: A blood test that shows blood glucose levels from the past 2-3 months by measuring the amount of glucose attached to hemoglobin, the oxygen-carrying protein in your blood. This test does not require fasting.
Random Blood Glucose Test: A blood glucose of over 200 mg/dL or higher at any given time suggests diabetes.
Fasting Blood Glucose Test: A blood sample taken after not eating the night before.
Glucose Tolerance Test: Fasting blood sugar is measured first, and subsequent blood sugar levels are tested after drinking a sugary liquid.
Different Types of Sugar
While glucose is our main energy source, fructose and galactose are two additional types of sugars we consume. These sugars are called monosaccharides, the simplest carbohydrates that build more complex carbohydrates such as lactose, maltose, and sucrose. Galactose and glucose together make lactose, the “milk sugar.” Conversely, maltose is two glucose molecules, and sucrose is one glucose and one fructose. Fructose is known as “fruit sugar” because it is primarily found in fruits and is a sweeter sugar than glucose. Fructose does not raise blood sugar the same way glucose does because the liver metabolizes it and does not require the release of insulin.
The sugars added to food such as breakfast cereals, baked goods, granola bars, and soft drinks are simply the sugars outlined above. For example, high fructose corn syrup is derived from corn starch and is a mixture of glucose and fructose, and corn syrup is a pure solution of glucose.
Should Sugars Be Created Equal?
While carbohydrates are an essential macronutrient in our diet, many of the foods we eat have added sugars, leading to our increased daily consumption. The American Heart Association recommends a strict limit on added sugar, with adult males consuming no more than 36 g of added sugar per day and adult females no more than 25 g of added sugar per day. The sugars found naturally in fruit and those in a candy bar have the same composition, but they each elicit a different physiological response after consumption. Fruit contains fiber and nutrients that provide additional nutritional value not available in a candy bar. In addition, a candy bar will make your blood glucose rise and fall rapidly, potentially causing a sugar crash. On the contrary, fruit has a lower glycemic index and will not cause blood sugar to spike and fall drastically. Overall, sugar is not to be feared, but be mindful of your daily sugar consumption and aim to get most of your sugar from a whole-food diet.
References:
Are certain types of sugars healthier than others? - Harvard Health
Ask the Doctors - Which spikes blood glucose more? Sugar in fruit or food? | UCLA Health Assessed and Endorsed by the MedReport Medical Review Board