January 18, 2021

Macronutrients Series: Breaking Down Carbs

Warning: this post is science-heavy. If you’re into it, please enjoy! If you’re not into it, scroll all the way down for the bottom line message.


Alright, let’s start with the basics, my friends! One of my first grad school classes in nutrition reviewed the macronutrients across an entire semester. What are macronutrients? I didn’t even know this when I started school, and I will never forget how much sense everything started making when I began learning about this. Macronutrients = carbohydrate, fat, protein. These macronutrients are what give us energy (i.e., calories) from foods. Think of them as the building blocks of our food. We need all 3, and all 3 have different functions in our body. A well-balanced meal has all 3 macronutrients. This is what helps us 1) get the various nutrients we need, 2) feel satisfied and full after eating.

Wheat Bread CarbsGet ready, science coming in hot! 

What are carbs?

Carbohydrates are molecules made from carbon, oxygen, and hydrogen. They are the primary energy source for our body. There are simple carbohydrates and complex carbohydrates. Simple carbohydrates include monosaccharides (meaning 1 sugar unit) like glucose, fructose, and galactose, as well as disaccharides (2 sugar units) like lactose, sucrose and maltose.

Where are carbs found?

Glucose and fructose are found all over the place, in fruits and other plants as well as in corn syrup and other additives used to sweeten food. Lactose is the type of sugar found in milk and milk products. Sucrose is cane sugar and the most commonly used sweetener. Complex carbohydrates have at least 3 sugar units, many of which fall into the category of polysaccharides like starch, glycogen and dietary fiber. We find these types of carbs in beans, peas, legumes, vegetables, and whole grains.

How are carbs digested?

Foods we eat have a mixture of simple and complex carbs. During the digestion process, our body breaks down all of these carbs into their basic 1-sugar units. This allows the sugars to be absorbed into cells in our intestines, and then they pass into the blood. This is why we can measure blood sugar because sugar uses the bloodstream as a highway to get to other cells in our body.

On that highway, the first stop for many sugars (and proteins) is the liver. The liver is like a filtration station for substances we take in. The liver can store some of the sugars and send some back into the bloodstream highway to the heart and ultimately to the rest of our body so our cells can use the sugar as energy. The liver sends on many of the sugars, but it realllllly likes to hold on to fructose and galactose. This is why diets high in fructose (I’m talking lots of sugary foods sweetened with high-fructose corn syrup and such, NOT someone who eats a few fruits a day) can lead to problems. Our livers ho