There are different kinds of carbohydrates, and terminology surrounding carbohydrates and sweeteners can be confusing. This section helps clarify carbohydrates and sugar.
Carbohydrate terminology and types of carbohydrates
Monosaccharides (from Greek monos: single, sacchar: sugar), also called simple sugar, are the most basic units of carbohydrates. They cannot be further broken down to simpler chemical compounds. The most common monosaccharides include glucose (you may also here this referred to as dextrose), fructose, and galactose.
Monosaccharides are the building blocks of disaccharides (from Greek di : two, sacchar: sugar). Disaccharides are 2 monosaccharides linked together by a glycosidic bond. Common disaccharides include sucrose (table sugar, also found in the fruit and roots of plants), lactose (found in milk), maltose (found in germinating grains), and trehalsoe (found in mushrooms).
Monosaccharides are also the building blocks of polysaccharides (from Greek poly: many, sacchar: sugar). These are much larger carbohydrates and are commonly referred to a complex carbohydrates. The most common complex carbohydrate is starch. Starch is a polysaccharide made by plants that humans are able to digest. Starch serves an important purpose in plants: it stores energy for the plant. It is made glucose units chained together in long strands to form enormous molecules. There are 2 forms of starch, amylose and amylopectin. When we eat starch, both amylose and amylopectin are slowly broken down (digested) in the digestive tract into thousands of glucose molecules, and then absorbed into the bloodstream where they are used as energy. Because of how large the molecules are, digestion down to glucose is slow and therefore tends to cause a slower rise in blood sugar level.
Fiber is another polysaccharide made by plants, with cellulose being a common example. Whereas the purpose of starch in a plant is to store energy, fiber’s purpose in the plant is to provide structure to the plant’s cells. Also unlike starch, humans cannot digest fiber into individual monosaccharides and absorb them into the bloodstream. Instead, fiber passes through the intestines undigested. Fiber is highly beneficial to the human diet. First, it provides bulk to help reduce hunger without adding calories. Second, it helps slow down the absorption of digested starches into the bloodstream, thereby blunting the fluctuation in blood glucose levels.
Fiber comes in 2 forms:
- Soluble fiber, which dissolves in water, can help lower glucose levels as well as help lower blood cholesterol. Examples of vegetables with high soluble fiber content include oatmeal, nuts, beans, apples.
- Insoluble fiber, which does not dissolve in water, can help food move through your digestive system. This promotes regularity in bowel movements. Examples of foods with high insoluble fiber content include wheat, brown rice, legumes, and carrots.
Sugar
Sugar is found in table sugar, brown sugar, molasses, honey, powdered sugar, cane sugar, raw sugar, agave nectar, corn syrup, maple syrup. You may see it listed on food labels as glucose, fructose, dextrose, maltose, and sucrose.
Sugar, like all carbohydrates, contains food energy. Every gram of carbohydrate has about 4 calories.
Sugar alcohols
Sugar alcohols are a type of reduced calorie sweetener and may be found in products that are labeled “sugar-free” or “no sugar added.” This includes sugar-free candies, desserts, and protein bars. Don’t be fooled – sugar alcohols are still a form of carbohydrate, and they still affect your blood sugar levels. Because sugar alcohols are harder for the body to digest, the effect on blood sugar levels is less than sugar. Sugar alcohols have about half the amount of calories compared with sugar.
Examples of sugar alcohols include sorbitol, xylitol, mannitol, isomalt, maltitol, lactitol. If you are counting carbohydrates, subtract half of the grams of sugar alcohol listed on the food label from the total grams of carbohydrate.
Artificial Sweeteners
Artificial sweeteners give the sweet taste of sugar, but have no carbohydrates or calories and do not raise blood sugar levels. There are 4 common artificial sweeteners:
- Aspartame (Brand Name: Equal)
- Sucralose (Brand Name: Splenda)
- Acesulfame-K (Brand Name: Sweet One)
- Saccharin (Brand Name: Sweet and Low, Sugar Twin)
Note that while these products are substances are not carbohydrates, the powdered forms of these substances are mixed with a small amount of sugar (to give them bulk). Each packet of these sweeteners has about 1 gram of carbohydrate. On the other hand, the liquid forms of these substances do not have any added sugar and truly have zero carbohydrates.
Finally, Stevia is a naturally sweet herb that is without calories or carbohydrates.
Net carbohydrates vs total carbohydrates
Net carbohydrates are sometimes referred to as digestible carbohydrates. The terms refer to carbs that are absorbed by the body. When you eat a carb-containing food, most of the carbohydrates are broken down into individual monosaccharide units by enzymes produced in your small intestine. Your body can only absorb monosaccharides.
Fiber cannot be digested into monosaccharides and sugar alcohols can only be partially digested. Because of this:
- Fiber can be subtracted from total carbs when calculating net carbs.
- 50% of grams of carbohydrate from sugar alcohols can be subtracted.