So carbs! They get a bad rep, but the truth is they are essential in our diet. My goal with this series of Back to Basics is to straighten out the confusion and misinformation on nutrition, starting with carbohydrates. I find that a lot of people see carbs as the enemy – its gets the most attention out of all the macronutrients especially on the topic about weight loss. Although, we all have good intentions to do right thing there is a lot of information out there that is incomplete. Statements are made, some are exaggerated, others are taken out of context and that's where people get confused. People obsess over carbs and take things to extremes by trying to cut them totally out of their diet - in which may I say is impossible. Carbs are in almost everything, including fruits and vegetables. It’s all about moderation and making sure we stay within certain limits. It’s absolutely okay to have carbs. Our bodies NEED them. We just have to make sure we have a middle ground because anything outside of that is where we see adverse effects on our health.
Our diets are broken down into three main food groups called macronutrients (or macromolecules): carbohydrates, fat, and protein. Each macronutrient plays a number of roles in our body.
WHAT ARE CARBS?
So let’s get into some basic chemistry a little bit….
Carbohydrates are made up of hydrogen, oxygen, and carbon atoms. The structure of these atoms make up a sugar molecule, also known as a saccharide. Saccharides are a family of sugars that are divided into four groups based on how many sugars are in each saccharide.
- 1 sugar = (mono)saccharide
- 2 sugars = (di)saccharide
- 3-9 sugars = (oligo)saccharide
- 10 or more sugars = (poly)saccharide
So monosaccharides are the simplest form of sugar, which make them the building block of all the other saccharides (disaccharides, oligosaccharides, polysaccharides). Think of them as Legos.
TYPES OF CARBS
So the different groups of carbs can be divided into two types: simple and complex. These two types act differently in the body. Simple carbs are easy to digest so they spike sugar levels and are quick to be converted into fat. Complex carbs are slower to digest because they are larger molecules and contain fiber. Since they take longer to digest they don’t spike sugar levels up. Complex carbs often contain more vitamins, minerals, and are protective against disease.
Simple Carbs (1 to 2 sugars)
Monosaccarides: glucose, fructose, galactose
Disaccharides: maltose, sucrose, lactose
i.e.: Processed (white, refined) bread, pastas, and rice, sweets, sodas, fruit juice, fruits, and some vegetables.
Complex Carbs (3 or more sugars)
Polysacchides: starch, glycogen, amylose
i.e.: Unprocessed, 100% whole grain bread and rice, legumes, nuts, seeds, and starchy vegetables.
HOW DOES OUR BODY USE CARBS?
Carbohydrates have many roles in the body. Different structures, as the ones mentioned above, execute different functions.
- Energy: carbohydrates are metabolized (broken down) to its simplest form, glucose, for energy. Once the glucose fulfills the body’s need for energy the excess is then stored in the liver, muscles, and and then fat cells.
- Structure: carbohydrates make up part of the cell membrane in our body’s cells.
- Signal transduction: carbohydrates play a part in cell-to-cell communication by transferring signals to other cells in the body.
- GI health: carbohydrates feed the good bacteria in our gut to help fight off against infection and break down nutrients so we can absorb them.
- Brain: uses glucose as it’s preferred source of energy, about 120 grams per day. It uses about 60-70% of our total body glucose stores. Brain function becomes severely affected when glucose falls below a certain threshold where it can be permanently damaged. The body will do what it can to compensate for the lack of glucose by using energy from alternative sources in the form of ketones, but this puts the body in a stressful state and unless someone is under the care of a doctor or requires a ketone diet (to treat epilepsy) it’s not recommended.
- Muscles: use glucose as it’s preferred source of energy as it’s more readily available for movement. It has the ability to store excess glucose in the form of glycogen (a more complex molecule) up to about 300-400 grams, which translates to about 1,200-1,400 units of energy. For the average adult this will typically last 12-14 hours. For an athlete exercising at a moderate level, such as marathon running, the muscle glycogen supply will last for about 2 hours.
- Liver: as I like to say the “heart” of metabolism! The liver uses glucose as energy for all of its processes to metabolize everything we eat. It works to breakdown each macronutrient into its simplest forms, signals for “storage mode”, “starvation mode”, “fight or flight mode” and more – basically any process that provides energy for the body to meet its needs and survive.
- Kidneys: help to manage our blood pressure and create urine to remove any fluid, electrolytes, and sugars from the bloodstream. Kidneys do a great job at backing up the liver by balancing our blood sugar and reabsorbing any sugars, fluid, and electrolytes needed by the body before releasing them in urine.
- Fat cells: use glucose as energy to fuel the process of storing fat. Any excess carbohydrates are run through a set of conversion processes to create triglycerides (fatty acids) which are stored in our fat cells in an effort to preserve energy for later in times of starvation.
AREN’T OUR BODIES AWESOME?!
They really are fascinating and have wonderful ways to make sure we stay alive.
DIGESTION OF CARBS
Digestion of carbohydrates starts in the mouth where the digestive enzyme amylase is released. The food or bolus then continues to move down into the stomach where stomach acid breaks down the carbs into smaller sugars. The food, now called chyme, passes through the stomach and enters into the small intestine where more digestive enzymes are released to break down the smaller carbohydrates into monosaccharides. Monosaccharides are small enough to be absorbed in the small intestine and from there they travel to the liver. The liver checks in with how the body is doing and then distributes the energy wherever it is needed. Glucose will be released in the body for immediate needs and then stored in the liver, muscles and adipose tissue (fat). Other carbohydrates that aren’t absorbed in the small intestine will continue through to the large intestine and into the colon. These carbs are more complex and/or fibrous (fiber) and are partly digested by the bacteria in the gut. Unlike other carbohydrates, fiber cannot be digested and absorbed in the large intestine or colon. Their function is to provide structure to our stools and clean out the digestive tract.
HOW MUCH DO I NEED?
Everybody’s body is different and everyone’s metabolism is different. No two people are the same. There are a number of factors that play into this such as age, gender, stress, activity-level, sleep, injury, genetics, disease, and culture. They all have to be accounted for as they all play a role in how much energy our body requires. It’s best to talk to a registered dietitian so you can get a full dietary assessment and accurate energy intake requirement.
I hope this 101 helped you understand carbs better and how are body uses them. For part 2 of this I would like to help you apply this information: what are good sources of carbs, what are the right portions, and timing your intake so that you prevent energy crashes. This information will be great for anyone especially if you are struggling with eating nutrient-rich carbohydrates. Please comment below if you have any questions or would like me to dig deeper into this. I would love to know what my readers would like to know about carbohydrates!