I’m excited to introduce to you my Nutrition 101 series! I’ve created this series to simplify complex nutrition topics and help cut through the misinformation out there in the health and wellness world. To put it bluntly, I’m calling out the bullshit and giving you the evidence-based facts. Nutrition is a complex science can be extremely confusing, especially with the different diet trends and health claims flooding social media. In this Nutrition 101 series I’m simplifying nutrition topics without cutting corners, so you’ll know the facts and feel empowered to use this information to make the best nutrition choices for your body and lifestyle.
First up, carbohydrates 101. Carbohydrates can be a confusing topic since there is a wide range of carbohydrate rich foods and not all of them are created equally. Often times, carbohydrates are viewed as “bad” and avoided in order to lose weight or reduce body fat. This is becoming more prevalent as gluten-free, grain-free, and paleo diets continue to grow in popularity.
The fact is your body needs carbohydrates to function optimally. In this post, you’ll find out what is a carbohydrate, the various types of carbohydrates, and the role carbohydrates play in the body. I’ll also cover how carbohydrates are digested and how much individuals typically need.
The first part of this post is a little science-y but hang in there! Let’s get a little nerdy and break down the science of carbohydrates…
What are Carbohydrates?
Simply put, carbohydrates are sugar molecules.
On a molecular level, carbohydrates are macronutrients made up of hydrogen, oxygen, and carbon. The way these atoms are organized make a “saccharide” (aka a sugar molecule). Depending on the composition, saccharides can be categorized into 4 groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
Monosaccharides are the simplest form of sugar and are the building blocks of disaccharides, oligosaccharides and polysaccharides. The three monosaccharides are glucose, fructose, and galactose. When paired, they form the disaccharides. The most important disaccharides in human nutrition are sucrose (table sugar), lactose (milk sugar), maltose (least common, present in germinating seeds).
When more than two sugar molecules combine they form oligosaccharide (fructooligosaccharides (FOS)) and polysaccharides (starches, dietary fibers, and glycogen).
Types of Carbohydrates
Carbohydrates can further be categorized as simple or complex.
The length of the sugar molecule (saccharide) determines which how they are classified. The simplest carbohydrates are referred to as sugar and are naturally present in fruit, milk and other unprocessed foods like honey and maple syrup. These naturally occurring sugars can be refined into table sugar and processed-syrups. These are then added to foods to provide sweetness. Simple carbohydrates require little digestion and raise blood sugar levels quickly.
Complex carbohydrates are made up of more than two sugar molecules. The way the molecules are arranged makes them digestible (starch) or non-digestible (fiber). Complex carbohydrates are found in whole grains, legumes, potatoes and other starchy vegetables. Complex carbohydrates take longer to digest and release into our blood sugar slower, therefore not elevating blood sugar levels as quickly.
- Most commonly referred to as sugar
- Smallest of the sugar molecules (monosaccharides and disaccharides)
- Some sugars occur naturally in foods (lactose in milk, fructose in apples), while others can be added to foods (like sucrose in candy, high-fructose corn syrup).
- Absorbed quickly, resulting in a spike in your blood sugar and energy.
- Most commonly referred to as starches and fiber
- Sugar molecules ranging from three to hundreds or even thousands of sugar units (oligosaccharides and polysaccharides)
- Starches are found in many foods such as grains, bread, oats and potatoes. The greater number of sugar molecules takes the body longer to break them down.
- Absorbed slower, resulting in a prolonged release of energy.
- Fiber is considered a complex carbohydrate but is not digested and is therefore not a source of energy for us. More on this later!
Functions of Carbohydrates in the Body
Carbohydrates are the body’s preferred energy source and a vital component normal metabolism and overall health. Here is an overview of how carbohydrates are used throughout the body.
- Energy – glucose is the main energy source for our cells. In fact, red blood cells and brain rely almost entirely on glucose as their energy source.
- Brain – uses glucose as its preferred source of energy, except in prolonged periods of starvation. The brain needs a constant supply of glucose because it does not contain any glucose stores. Uses about 120 g per day or about 420 calories. At a resting state this accounts for almost 60-70% of an individual’s glucose utilization.
- Muscles – when carbohydrate intake is adequate, it allows the amino acids from protein to build body tissues. When there are excess carbohydrates, it is stored in the form of glycogen in the muscles up to about 1200 calories. Think of this as your energy stores for when you are exerting energy (like working out). Fun fact: ¾ of all the body’s glycogen is stored in the muscles.
- GI health – fiber plays a huge role in maintaining the function of the GI tract and overall health by helping prevent constipation, feeding the good gut bacteria and helping manage our body weight, blood glucose levels, and blood cholesterol.
- Liver – the liver has a main role in metabolism of all macronutrients and its metabolic activities are essential for fueling the brain, muscles and other organs. The liver uses glucose to metabolize everything we put into our body. It is also able to produce glucose from glycogen stores when our blood glucose levels are low.
- Kidneys – small but mighty! These organs’ main job is to produce urine by filtering our blood of waste products and maintaining the balance of our body fluids. Our kidneys get rid of excess minerals, sodium, water, glucose, etc. that we don’t need and reabsorb the ones we do need. A large amount of energy in the form of glucose is needed to accomplish filtration and reabsorption.
- Fat cells – excess carbohydrates in the form of triglycerides are stored in our fat cells. Think of this as an energy reservoir that can be converted to energy at a later time.
Digestion of Carbohydrates
The goal of carbohydrate digestion is to break down the starch and sugars into the monosaccharides that can be absorbed by the small intestines and used as fuel.
This process starts in the mouth with the enzyme amylase produced in our saliva. As the food moves down into the stomach it mixes with stomach acid before moving into the small intestines. Once the food enters the small intestines, digestive enzymes are released from the pancreases and the carbohydrates are broken down into monosaccharides so they can be absorbed by the small intestines. The monosaccharides make their way through the blood stream to the liver. From there, the liver converts them to glucose to be used as energy. If there is excess, the liver stores the glucose as glycogen and it is used to maintain blood sugar levels. Once the liver storage is full it converts the excess glucose to fat storage. The non-digestible carbohydrates (fibers and resistant starch) that were not absorbed in the small intestines move along to the large intestines where they are fermented by bacteria or are excreted as waste.
How much do I need?
Technically, a minimum intake of 50-100 grams per day of carbohydrates is necessary to break down fats without producing ketone bodies. The Recommend Dietary Allowance (RDA) for adults states that adults need about 130 grams per day of digestible carbohydrates to supply adequate glucose for the brain. But as you can see from the information above, our bodies prefer carbohydrates. The general guidelines are to provide your body with 45-65% of total energy intake. So, for a 2000 calorie diet, this is anywhere from 225 grams to 325 grams per day.
However, depending on your age, gender, genetics, activity level, disease state, lifestyle, etc. this could be way too much or too little. If you really want to find out what is best for YOU, I recommend meeting one-on-one with a registered dietitian nutritionist. That being said, I find it more beneficial for individuals to focus of the type of carbohydrates (simple vs. complex) rather than getting too caught up with a specific number.
I hope this carbohydrate 101 helps simplify the basics of carbohydrates and the ways they help our body function optimally. Stay tuned for part 2 – carbohydrates 101, continued. This post will cover sources of carbohydrates, portion size of carbohydrates, my recommendations on eating carbohydrates.
Comment below if you have any questions or would like something clarified. I want to be a nutrition resource, so ask away below or feel free to message me here. Remember no question is “stupid”. I LOVE answering questions and want to help you feel confident in your nutrition decisions.