Carbohydrates are molecules composed of carbon, oxygen, and hydrogen (the oxygen and hydrogen combine to form H₂0, water, making “carbo-hydrates” a simple combination of carbon and water). Fundamentally, carbohydrates are sugar molecules linked to one another in varying arrangements. Carbohydrates are the preferred source of energy for your body to fuel working muscles and the central nervous system, enable fat metabolism, and prevent protein from being burned as energy. Because muscles use glucose to contract, low blood glucose (more commonly referred to as “low blood sugar”) diminishes athletic performance. More importantly, the brain needs glucose, and thus carbohydrates, to function properly.¹

Carbohydrates fall into two general categories: simple and complex. Complex carbohydrates are multiple sugar molecules linked together in a complex way and can be likened to time-release capsules of sugar. On the contrary, simple carbohydrates are just a few (usually 1 to 3) sugar molecules linked together that the body can quickly process. Simple carbohydrates can be likened to sugar injections. Complex carbohydrates, which are known as “starch,” are often deemed to be "more healthy" than simple carbohydrates because they provide sustained energy, not a sugar spike, and tend to come from healthier foods. Complex carbohydrates provide sustained energy because of their time-release effect that creates a slow and steady increase in blood glucose and insulin levels. The time-release effect is due to the cellulose fiber coating that surrounds complex carbohydrate cells and slows digestion and absorption. Cellulose is comprised of long glucose polymers and forms the cell walls of all plants.

Although carbohydrates are typically categorized as “simple” or “complex,” there are actually three types of carbohydrates:

1. Monosaccharides are simple sugars that serve as the building blocks of carbohydrates. Mono means one and saccaride means sugar. Hence, “one sugar.” There are three common types of these simple sugars: glucose (blood sugar levels are measured using glucose), fructose (fruit sugars), and galactose (a type of sugar found in dairy products). All three share the same molecular formula, but the arrangement of atoms differs in each. When people talk about “blood sugar levels,” they’re talking about the amount of glucose floating around in the blood.¹

2. Oligosaccharides are short chains of several monosaccharides linked together in chain-like structures with covalent (hydrogen) bonds. Oligos is Greek for a few, so a “few” sugars.¹

3. Polysaccharides are long chains of three or more monosaccharides. The two major polysaccharides that are important for physiology are starch (polysaccharides made exclusively by plants) and glycogen (polysaccharides made exclusively by animals).¹

The body doesn’t recognize that different types of sugar are being ingested. Whether it is fructose from a banana, glucose from a Snicker’s bar, or galactose from whole milk, the body cannot recognize the difference. Upon digestion, the body breaks down all of these carbohydrates into monosaccharides, and converts the non-glucose monosaccharides (from fructose and galactose) into glucose through the liver. Galactose is not able to be processed by the body and ends up functioning like dietary fiber. In other words, all forms of carbohydrates are either metabolized into glucose or are left undigested, serving as dietary fiber.²

The only difference between the carbohydrates from a Snicker’s bar and a banana is how fast they are processed and utilized by the body. This is not to say that a Snicker’s bar and a banana are comparable. Obviously, fruits are MUCH more nutritious than candy bars! For optimal health, you should aim to get the majority of your carbohydrates from whole, unprocessed foods like fruits, vegetables, and grains.¹

Foods high in carbohydrates include grains and fruits. Dairy products and vegetables also have small amounts of carbohydrates. Processed foods, especially those high in refined sugar, generally contain high amounts of carbohydrates. All living cells rely on glucose to function properly. Your body breaks down sugars (carbohydrates) into monosaccarides and then glucose, which your body transports to your brain, muscles, and organs for use. If glucose is not needed right away for energy, it will be stored in the liver and muscles as glycogen to be used later. An average adult can store approximately 500 grams of carbohydrates or 2,000 kcal (500 grams x 4 kcal per gram) in the liver and muscles for future use. Of these 500 grams, approximately 400 grams will be stored as muscle glycogen, 90-110 grams as liver glycogen, and 25 grams will circulate throughout the bloodstream. Specific muscles can only use the glycogen stored within them and cannot borrow from another muscle’s glycogen stores. If the glucose is not needed right away for energy and the body’s carbohydrate stores are full, the body will store glucose as fat.²