What are Carbohydrates?
We need energy for everything. Going to the gym to work out is an obvious one, but we also need energy to get up and walk around, perform tasks of daily living, and use our heart, brain, lungs, and other organs. There are three macronutrients that provide energy for the body: carbohydrates, fat and protein. The body cannot produce macronutrients on its own, so they must be obtained through the diet. Carbohydrates are the body’s preferred energy source, so we need more of them than protein and fat. The different carbohydrate types include sugar, starch, and fiber. We function better when the body is fueled with optimal levels of carbohydrates from various carbohydrates sources through our diet. For the general public, it is recommended by the experts to consume 45-65% of daily calories from various carbohydrates sources. On a typical 2000 calorie diet, this would be 225-325g carbohydrates per day.
How are carbohydrates used in the body?
It is easiest for the body to get its energy from carbohydrates sources. This allows the body to use fats and proteins as building materials for cells, or to store them away for use later. When the body is deprived of carbohydrates, it must begin to breakdown protein and fat as energy. Not only is this stressful to the body, but also less efficient and potentially dangerous. Depending on the state of the body at the time of consumption, the body will decide on how to best utilize the carbs. They may be directly transformed into glucose to be used for energy or stored for later use as glycogen if energy is not needed immediately.
The body breaks down the different carbohydrate types into smaller units called glucose and fructose. The small intestine absorbs these units into the bloodstream where they travel to the liver to be converted into functional glucose. The liver then releases that glucose into the bloodstream where it travels throughout the body to provide energy to the cells. Once the body has been properly fueled, leftover glucose is stored as glycogen in the liver and muscles. We use stored glycogen to fuel us when we have gone too long between meals, or in times of high energy expenditure such as exercise. Once those glycogen stores are full, the body will store excess carbohydrates as fat. While it is important to consume enough carbohydrates to fuel us throughout the day, excess carbohydrate storage can cause weight gain if it is not used up as energy.
The more glucose present in the blood, the higher our blood sugar. As you can imagine, after eating a meal there is an influx of glucose in the blood, causing a spike in blood sugar levels. The body manages these spikes through hormones like insulin and glucagon to keep blood sugar in the optimum range. At least this is the case in a healthy individual. For those with diabetes, the body has difficulty producing insulin which means it has trouble processing a high concentration of glucose. In this case, a lower intake of carbohydrates is typically recommended in order to sustain energy while preventing uncontrolled spikes in blood sugar levels. To prevent these blood sugar spikes, it is recommended to consume mostly complex carbohydrates.
Simple vs complex carbohydrates
While all carbohydrate types are broken down into sugars that give the body energy, they are not created equal. Simple carbohydrates digest quickly in the body and include table sugar, honey, dairy, some fruits, and fruit juice. These carbohydrates can be used for quick bursts of energy, but will not last long and contribute to a spike and drop in blood sugar levels. Complex carbs on the other hand digest more slowly and include bread, pasta, grains, crackers, some fruits, vegetables, and legumes. Most people get the majority of their complex carbs from grains which can be divided into two carbohydrate sources – whole grains and refined grains. Refined grains are those that have been processed and are no longer in their whole and natural form. This can include white rice, and white flour used in white bread, crackers, chips. Whole grains contain more fiber, vitamins and minerals. Examples of whole grains include brown rice, whole grain bread and pasta, oats, and popcorn.
Why do carbs get a bad rap?
If carbohydrates are so important for energy maintenance, why do they get such a bad rap? Every modern diet seems to consist of some element of carbohydrate reduction. From the keto diet on the extreme end to low carb paleo, south beach, and atkins to name a few. Carbs are demonized in today’s society. Why? This boils down to diet quality, and consuming the right carbohydrate types from the right carbohydrates sources.
The different carbohydrate types
There are a few types of carbohydrates you should be aware of:
- Added sugars are simple carbs that are added to foods during processing to enhance sweetness. This carbohydrate source includes honey, cane sugar, brown sugar, maple syrup, fruit juice concentrates and other syrups. Overconsumption of added sugars has been a great topic of discussion among healthcare professionals. An increased consumption of added sugars has been directly linked to obesity. While these sugars will indeed be used as glucose for energy in the body, they are considered “empty calories” because they have high caloric value but do not contain any vitamins, minerals or fiber. Added sugars will not keep us full, and as a result cause us to overeat.
- Fiber is a carbohydrate type that is not broken down in the small intestine during digestion. Instead, it slows the digestion process keeping us full longer and travels all the way to the large intestine where it plays a protective role in gut health, bowel function, fullness, and blood sugar regulation. It includes psyllium, which is found in whole grains, fruit and legumes such as beans. Fiber plays an important role in prevention of chronic diseases such as heart disease and diabetes.
Western diets are typically higher in simple carbohydrates such as added sugars from processed and fast foods, and lower in fiber and complex carbohydrates such as fruit, vegetables and whole grains. This diet pattern is often accompanied by low levels of physical activity as well. Since excess carbohydrates are stored as fat, weight trends as well as levels of chronic disease have been steadily increasing as a result of this diet pattern. This is often misinterpreted and leads many to believe that eating less carbs is the best way to lose weight and be healthier. Carbs are our friends! Rather than shunning them we should instead consider carbohydrate type, carbohydrate source, and the ratio of carbohydrates to protein and fat. For example:
- A banana split from Dairy Queen contains about 94g carbohydrates and only 4g of fiber.
- A chicken breast, ½ cup of brown rice, ¼ cup black beans and 1 cup of broccoli contains only 40g carbohydrates and 10g fiber.
In this example, option A is 100% simple carbohydrates: dairy, fruit and added sugars. While it will give us an immediate boost in energy, it contains almost half a day’s recommended carbohydrates while it is low in fiber and does not contain protein or other nutrients to sustain us. Option B however, has 100% complex carbohydrates from the rice, beans, and broccoli, and has significantly less carbohydrates, double the fiber, protein and many other nutrients to sustain us for much longer. While having option A can be a part of a balanced diet if portion sizes are considered, option B will provide us with much more stable energy as it contains all three macronutrients.
List of different carbohydrate sources
As mentioned, carbohydrates are an important part of the diet. Try and include a variety of fiber-rich fruit, vegetables and whole grains in the diet for sustained energy throughout the day, diversity of nutrients as well as nutrient density, or high ratio of nutrients in relation to calories. Some examples of whole grains include:
- Brown rice, barley, quinoa, amaranth, farro, wild rice, oats, bulgur, popcorn
- Whole wheat pasta
- Whole grain bread
- Variety of fresh fruits and vegetables
Written By Marissa Gusmao Edited by Alexander Franz Reviewed by Morgan Murdock, RD.
- https://med.libretexts.org/Courses/American_Public_University/APUS%3A _An_Introduction_to_Nutrition_(Byerley)/Text/03%3A_Carbohydrates/3.03%3A_Digestion_and_Absorption_of_Carbohydrates