Do All Carbohydrates Turn to Sugar In the Body?
The misconception about Carbs
I FREQUENTLY get asked questions about carbohydrates- which are "bad"....which are "good"...and which "turn to sugar in the body."
The common misunderstanding involving carbs is often related to their effect on blood sugar. This relationship between carbohydrates and blood sugar is important to understand because it clears up a lot of the confusion as to which carbs are best for weight loss/weight management and why.
There are two types of carbs- simple and complex- which I will explain in a moment, but what you NEED to understand is that BOTH types of carbs are digested and released into the bloodstream as glucose (SUGAR) which is then used as fuel for our bodies to train, to perform normal daily activity and to execute essential bodily functions.
In other words- simple carbohydrates are NOT the only carbohydrates that become sugar in the bloodstream. Complex carbohydrates do as well. What differs is the way in which the carbohydrates are digested, and the rate of digestion.
Simple versus Complex Carbs
Simple carbs include fructose, or fruit sugar; lactose, which is milk sugar; and sucrose, more commonly known as refined white sugar. Simple carbs are classified as being "simple" because they EASILY break down in one simple step in your gut. For example when you eat an apple, simple carbohydrate fructose molecules head directly to your small intestine. From there, they quickly convert to glucose and absorb into your bloodstream through intestinal walls. The same process occurs from lactose in milk, or sugar from a candy bar.
Complex carbohydrates, which are starches in bread and potatoes, are long complex branches that take longer to digest. Complex carbohydrate molecules need more work to convert to glucose. For example when you chew a piece of sprouted grain toast or have a spoonful of mashed potatoes, saliva surrounds complex starch molecules and begins breaking them down into what's known as maltose. Even though maltose is a simple type of carbohydrate, enzymes in your small intestine have to then break it down further into smaller glucose molecules. Once complex starch molecules are broken down into glucose, THEN they enter your bloodstream through the intestine.
So even though the digestive process of simple and complex carbohydrates differs, the end result is the same: SUGAR.
Glucose & Glycogen
Glucose is simply sugar. Glycogen is the term for STORED SUGAR. When you eat carbohydrates, your body uses the glucose it needs from those carbohydrates right away and then stores the rest as glycogen in your liver and muscles.
As I mentioned, glycogen is the term for stored sugar. It is a complex polysaccharide carbohydrate that your system can quickly convert to glucose when carbohydrates from food are not available.
For example, during a vigorous workout, your body turns to your glycogen stores to get the energy it needs to fuel cells. You may feel fatigued early on in your workout if you do not eat ahead of time. This occurs because your body is burning glycogen and your overall glycogen stores become diminished.
This is also why it's popular practice to eat carbohydrates post workout to help restore glycogen levels.
What about Fiber?
Fiber is an exception, since it is a complex carb but it does not break down into glucose. This is often why it's a popular school of thought to eat more fibrous carbohydrates because they don't break down into glucose in the same way.
When consumed, fiber keeps its form in your digestive tract and helps push out waste. Fiber is an essential type of carbohydrate to have in your diet for digestive and bowel health, however too much can cause adverse reactions as well. You can get fiber in your diet from plant foods, including fruits, vegetables, grains and legumes. The dietary guidelines are to consume 14 grams of fiber for every 1,000 calories you consume. So based on a 2,000-calorie diet, you would need about 28 grams of fiber each day, pulling from both soluble and insoluble sources but fiber intake is, in my opinion, HIGHLY individualized so you may find you need more or less of one kind of fiber than another (soluble versus insoluble) or more or less TOTAL fiber overall.
How does fructose differ from glucose?
Fructose is a sugar found naturally in many fruits and vegetables, and added to various beverages such as soda and fruit-flavored drinks.
However, it is very different from other sugars because it has a different metabolic pathway and is not the preferred energy source for muscles or the brain.
Fructose is only metabolized in the liver and relies on fructokinase to initiate metabolism. It is also more lipogenic, or fat-producing, than glucose. Unlike glucose, too, it does not cause insulin to be released or stimulate production of leptin, a key hormone for regulating energy intake and expenditure. These factors raise concerns about chronically high intakes of dietary fructose, because it appears to behave more like fat in the body than like other carbohydrates.
It ALSO makes fruit a sub optimal choice for restocking depleted glycogen stores from training (aka post workout meal) because fruit restocks LIVER glycogen, NOT muscle.
Should I avoid sugar or sucrose?
Sucrose is commonly known as table sugar, and is obtained from sugar cane or sugar beets. Fruits and vegetables also naturally contain sucrose.
When sucrose is consumed, the enzyme beta-fructosidase separates sucrose into its individual sugar units of glucose and fructose. Both sugars are then taken up by their specific transport mechanisms. The body responds to the glucose content of the meal in its usual manner; however, fructose uptake occurs at the same time. The body will use glucose as its main energy source and the excess energy from fructose, if not needed, will be poured into fat synthesis, which is stimulated by the insulin released in response to glucose.
Sucrose has both positive and negative health implications. Consumption of adequate sucrose ensures your body gets the optimal amount of energy but uncontrolled high levels of sucrose can result in sugar-related diseases, such as diabetes. Obesity or weight gain may also occur due to the conversion of excess sugar to fat, which is then stored in adipose tissue and around your joints and organs.
The health claim of "avoid sugar" comes mostly from the fact that simple carbohydrates tend to contain MORE sucrose. They also are digested more rapidly so they tend to elevate blood sugar rapidly, which can lead to weight gain. The glycemic index is a ranking of how quickly carbohydrates raise blood sugar. Foods with a low glycemic index are more slowly digested, so they don't cause large spikes in blood sugar levels. Typically these foods are LOW sucrose foods, and are complex fiber rich carbohydrates, which is why most health professionals suggest consuming those foods. However its important to remember that we seldom eat foods in single units. Just a banana. Just a piece of toast. Often we eat foods in combinations- like a banana with peanut butter or toast with butter. And anytime to consume a carbohydrate alongside protein or fat it automatically SLOWS the rate of digestion, thus altering the blood sugar impact or glycemic index rating. So if you DO eat a more "simple" carbohydrate, if you combine that food with a food that has a lower glycemic index, like a protein or a fat, it doesn't have the same negative health impact as it would have if you ate it by itself.
Are complex carbs best?
Simple carbohydrates are digested very quickly and cause cause a rapid surge in blood glucose levels. Your body responds promptly by releasing large amounts of insulin, to drive the glucose into most cells and restore blood glucose levels. In the cells glucose is burned for energy, stored as glycogen or transformed into and stored as fat.
Your body has a tendency to ‘overreact’ to large surges in blood glucose by producing too much insulin resulting in a large dip in glucose levels (i.e. hypoglycemia). In eating a lot of simple carbs the release of insulin and blood sugar levels follows a peak and trough pattern, i.e. highs followed by lows.
The ‘lows’ in blood glucose are accompanied by fatigue, brain fog, dizziness and weakness. It is also associated with hunger pangs and cravings which can lead to a vicious cycle of continuing to eat low nutrient foods that are high in sugar. This results in a day characterized by continual highs and lows.
Insulin also activates lipoprotein lipase – a fat storage enzyme. This enzyme acts as a roadblock for the removal of triglycerides (fat) out of fat cells by inhibiting lipase which functions in breaking down of stored fats.
SO- for efficient weight loss, it can be to your benefit to control your blood glucose and therefore your insulin levels. Your goal should be to keep these levels as even as possible and limiting your intake of refined and simple carbohydrates as much as you can will help.
Complex carbohydrates on the other hand, take longer to digest and are able to provide you with a more controlled release of blood sugar (and the corresponding insulin response). The result is that you get sustained levels of energy without the highs and lows in blood glucose and energy that you would experience with simple carbs. Complex carbs also tend to be more nutrient dense, which goes a long way towards balancing hormones and alleviating unwanted cravings. A nutrient dense diet also allows you to feel fuller for a longer period of time, and has been shown to prevent over-eating.
This is why, if you're focused on weight management or weight loss, it's recommended that you rely as much as possible on consuming more complex carbs.