Whether you're a armchair athlete or someone who enjoys playing soccer with the kids, your body depends on ample supplies of calories to fuel your body. And while most people are familiar with eating a balanced diet that comprises carbohydrates, fats and proteins, many tend to shy away from foods that are high in carbohydrates. The truth is that sugar broken down from carbohydrates is one of your body's most important fuels. It's readily accessible by most organs and tissues, available in large quantities and is the preferred fuel for your brain and muscles.
Sources of Glucose
Beginning as simple (monosacharides) or complex (polysaccharides) carbohydrates, glucose (also called blood sugar) is derived from the food we eat, then leaves the small intestines, where it enters the bloodstream. Simple carbohydrates are foods with basic molecular structures and are found in fruits and dairy products. Complex carbohydrates are molecularly more complex and are found in refined and processed foods like pasta, white bread and baked goods. One major difference between the two types of carbohydrates is how fast they are converted to glucose and enter the bloodstream. Because simple carbohydrates are easier to break down, they enter the bloodstream faster than complex carbohydrates.
While both types of carbohydrates are ultimately released into the bloodstream, there are major differences between the two and how they can affect your health. Many types of simple carbohydrates like candy, fudge and cakes enter the bloodstream rapidly and cause blood sugar levels to spike. Others like berries, grapefruit, apples and pears are better sources because they take longer to digest, reducing the time it takes for blood sugar levels to increase. Spiking blood sugar levels are particularly dangerous for diabetics.
Complex carbohydrates are structurally different, because they are made up of chains of carbohydrates that take longer to digest. These are found in vegetables, whole grain breads, brown rice and oatmeal that have higher contents of fiber. The combination of the structure and the fiber slow down the digestive process and release glucose into the blood at slower rates than simple carbohydrates. This makes them better choices for diabetics who are trying to maintain stable blood glucose levels.
Glucose as Fuel
Glucose that's released into the bloodstream acts as a ready supply of fuel for your body. Under normal circumstances, it's accessible, easy to process and fast acting for exercising muscles. Glucose circulating in the bloodstream is also the preferred fuel of the brain. Through its highs and lows, the body has finely tuned mechanisms to control how much glucose circulates in the blood.
Monitoring Blood Glucose
While it's important that the body has enough glucose to supply fuel for the body's immediate needs, it's also imperative that it maintains glucose levels at safe levels and stores extra fuel for times when glucose is in short supply. For short runs or hikes, there is generally enough glucose in the blood to meet the needs of exercising muscles, up to one or two hours. Anything longer than that requires constant replenishment through quick-acting gels, sports drinks or stored fuel. The principal hormone that regulates blood glucose uptake is insulin. Insulin is made in the pancreas and facilitates the glucose uptake of active muscles. If insulin is in short supply (such as type I diabetes), the muscles can starve in the presence of adequate glucose levels. Type II diabetics suffer from a different problem: They make plenty of insulin, but their muscles cannot use it. For both type I and type II diabetics, the results are the same: abnormally high levels of blood glucose while their tissues starve.
Tapping into Stored Glucose
Under normal circumstances, the body is capable of maintaining a safe range of blood glucose levels--usually 70 to 110 mg/dl. If the blood contains more glucose than it needs, it will store it for future use in the liver and muscles as glycogen. If blood glucose levels drop below a safe range (such as in extreme exercise like marathon running), it will tap into stored glycogen by releasing two hormones: epinephrine and glucagon.
Symptoms of Low and High Blood Sugar
If you've just completed a long hike, marathon, century bicycle ride or some other extended form of high-intensity exercise, you could experience temporary dips in your blood glucose levels. Glucose levels lower than 70 mg/dl is called hypoglycemcia and can result in extreme hunger, depression, headaches, an uncontrollable craving for sweets, nervousness and irritability, drowsiness, insomnia, anxiety or heart palpitations. The good news is that these symptoms are easily rectified by eating something sweet. Eating 4 to 6g of a highly concentrated glucose product like hard candy or fruit juice should get you back on your feet within 20 to 30 minutes.
On the other hand, symptoms like frequent urination, blurred vision, high blood pressure, extreme thirst, feeling weak or tired, having a dry mouth, unexplained weight loss and fluid retention could be signs of high blood glucose or hyperglycemia. Hyperglycemia is blood glucose levels of 110 mg/dl or higher and could indicate pre-diabetes. If you experience any of these symptoms, seek immediate medical attention. They could be signs of much more serious complications.