Mini Lesson: Carbohydrates

Video Transcript

Structure of Carbohydrates

Carbohydrates are considered a macronutrient, which means that our bodies need them in fairly large quantities compared to some other nutrients like vitamins and minerals. These nutrients are made up of a group of carbons with hydrogen and oxygen attached, which is why they are called Carbohydrates. 

The most basic forms of carbohydrates are monosaccharides, the most commonly known being glucose, fructose, and galactose. These saccharides can join together to form larger carbohydrate molecules. Disaccharides, where two monosaccharides are joined together, are simple carbohydrates we often refer to as sugar. Table sugar is sucrose and lactose is a specific sugar found in milk. More complex carbohydrate chains are considered to be starches or fiber, depending on how the saccharide molecules are joined together.

Digestion of Carbohydrates

Before carbohydrates can be taken in and used in the body, they have to be broken down to that individual monosaccharide level. There are enzymes released by the mouth and the pancreas that are designed to break down starches into small groups of saccharides, and the small intestine cells make special enzymes that will break disaccharides into their individual monosaccharides.

Absorption of Carbohydrates

The cells that line the small intestine have specialized molecules that will grab onto  different types of monosaccharides and pass them to the blood so that they can be used in the body. If carbohydrates are mostly eaten in their most simple forms, such as lots of added sugars or refined carbohydrates, these monosaccharides are quickly passed to the blood causing blood sugar levels to rise very quickly, which causes a lot of stress and panic in the body to manage that much sugar at once. More complex carbohydrates do no have the same effect on blood sugar levels because it takes the body time to break apart polysaccharides before they can be absorbed.

Function of Carbohydrates in the Body

In the body, carbohydrates are primarily used to produce energy. Our bodies can produce small amounts of glucose from the glycerol molecule that forms triglycerides, or amino acids, but there are a variety of foods that provide carbohydrates.

Food Sources of Carbohydrates

Plants are able to form carbohydrates out of carbon dioxide and water through the process of photosynthesis. Monosaccharides are joined to form fibers and starches that provide either structure or energy for the plant. This means that all plant-based foods will have some amount of carbohydrates, but the types of carbohydrate will depend on which part of the plant is being eaten.

Leafy green vegetables have mostly fiber to provide structure. Since our enzymes cannot break down fiber, these vegetables provide very little sugar or energy. Fruits and fruit-like vegetables, such as tomatoes and squashes, are filled with fiber for structure as well as starches that can be converted to more simple sugars as they ripen. So these foods provide more energy than leafy green carbohydrates, but the how much they have depends on the type of fruit or vegetable. Tubers, like potatoes, are like a little energy reserve for the plant, so these are generally quite a bit higher in starches. Root vegetables, like carrots or beets, tend to be a bit higher in fiber and less starchy than tubers. Plants also produce seeds that have quite a bit of fiber and starches.  Many seeds come packed with starches, vitamins, and minerals to ensure that the new plant will have plenty of energy and nutrients to get them started before they are able to produce their own energy and get the nutrients they needs from the soil.

Animals are also able to produce carbohydrates, though in drastically smaller quantities. Though milk contains the simple sugar lactose, meats, fish, poultry and eggs do not provide any significant amount of carbohydrates, if any.

Why Variety is Important with Carbohydrates

Although we often think of carbohydrate foods as providing energy for the body, choosing to eat a variety of whole food carbohydrate sources also provides important types of fiber, as well as vitamins and minerals to meet basic needs, and a variety of phytonutrients that support optimal health.