You may be familiar with how glucose, also known as blood sugar, rises and falls in the body, especially after you eat. For instance, if you haven’t eaten in a while and feel hungry, fatigued, and irritable, you may blame this on having “low blood sugar.”
While there is truth to this, glucose and how it is processed and circulates in the body has a significant impact on your energy, mood, cravings, sleep, metabolic health, and overall well-being. Even if you don’t have diabetes, pre-diabetes, or other metabolic dysfunction, it’s important to understand glucose and how it functions in the body.
Below, we explain what glucose is, where it comes from, and how it is used in our body on a daily basis.
What exactly is glucose?
Glucose is a sugar and is the simplest form of carbohydrate in the body. It’s technically known as a monosaccharide, or a simple sugar, meaning its chemical structure is one sugar molecule. There are other monosaccharides such as fructose and galactose, and there are sources of glucose that contain more than one sugar molecule. These range from the disaccharides such as lactose (a milk sugar) and sucrose (a common source of glucose found in table sugar and other sweeteners) to the more complex forms known as starches (polysaccharides). Any carbohydrate you eat, whether it’s the more complex brown rice, potatoes, bananas, or the simple sugar in your coffee, eventually gets broken down into glucose.
This glucose circulates in your bloodstream and provides your cells with energy. Glucose is essential for proper functioning of the body and is also tightly regulated by the hormones insulin and glucagon. Too much glucose in the bloodstream will cause a release of insulin to drive glucose into the cells to be used for energy or to be stored for later use. Too little glucose in the bloodstream will signal glucagon to release stored glucose to bring blood sugar back into the normal range. (1)
Where does glucose come from?
The primary source of glucose in our diets is carbohydrates. As mentioned above, the carbohydrates you eat are broken down into glucose in the blood. When we discuss how carbs get broken down into glucose, there are three main types of carbohydrates that are important to understand:
Sugars such as glucose, fructose (from fruit), sucrose (from plants), and lactose (from dairy).
Complex carbohydrates such as vegetables and whole grains (bran, amaranth, oats, quinoa) and starches such as rice, potatoes, and refined wheat flour.
Fibres, which are non-digestible forms of carbohydrates that can help feed healthy bacteria in our gut, keep our digestive system working properly, and reduce blood sugar spikes after meals. Fibre is found within complex carbs such as vegetables, seeds, beans and legumes, whole grains, and fruit. (2)
All carbohydrates are broken down into varying amounts of glucose, but the speed at which the glucose enters the bloodstream can vary depending on the type of carbohydrate you eat. Simple carbohydrates such as table sugar, candy, and soda contain either one or two sugars and are rapidly converted to glucose to be used for energy, causing a rapid rise in both blood sugar and insulin. (4)
Some additional examples of simple carbohydrates include:
- High fructose corn syrup
- Fruit juice
- Sports drinks
- Honey
Additionally, foods that have been heavily processed or have added sugars also act like simple carbohydrates in the body. These are foods like:
- Packaged crackers and pretzels
- White pasta
- Enriched flours
- Refined breakfast cereals
- Cookies
- Complex carbohydrates
Examples of complex carbohydrates include:
- Vegetables (broccoli, asparagus, leafy greens, spinach, cucumbers, squash, peppers)
- Fruit (berries, apples, pears)
- Legumes (lentils and beans)
- Unrefined whole grains (brown rice, quinoa, barley etc.)
Fruits such as berries, avocado, and passion fruit have more fibre than fruits with a higher water content such as cantaloupe, watermelon, and peaches. You may notice the impact on your glucose levels differ depending on the fruit that you eat.
If you’re wondering what happens if you include very little carbohydrates in your diet, know that you will still have glucose circulating in your system. This is because glucose can also be made from products of fat and protein metabolism through a process called gluconeogenesis. Even though glucose is an essential nutrient for life, it is not an essential dietary nutrient, given that our body can make its own through the process of gluconeogenesis. Gluconeogenesis typically occurs when our body is in need of glucose, such as during periods of prolonged fasting, vigorous exercise, or other activities that reduce our body's availability of glucose. This process is also driven by the hormones glucagon and insulin. (3)
What is glucose used for?
Glucose is a source of energy in the body — not just for humans, but also for every known organism in the world (yes, even plants!). When our bodies acquire glucose, whether through eating carbohydrates or generating it through the breakdown of glycogen or via gluconeogenesis, this glucose travels through the blood to supply energy to various tissues.
Our cells break down glucose in a series of biochemical reactions that eventually release ATP. ATP is needed for every energy-requiring process in the body, such as keeping our heart beating, breathing, and muscle contraction, and we would not survive without it. (1)
While there are many types of glucose transporters in the body, depending on the location and tissue type, the two main hormones that regulate glucose are insulin and glucagon. After a meal, especially a meal containing carbohydrates, our body releases insulin to move glucose into the cells to generate ATP (aka energy).
The more carbohydrates are consumed, the more insulin is required to move glucose into the cells and keep the glucose in our blood in a tightly regulated, healthy range. Once the cells have enough energy, the excess glucose is stored as glycogen in our liver and muscles. Once those stores are full, glucose will be converted to fat and stored for later use.
When we are fasting, such as when we are asleep at night, glucagon is released to liberate stored glycogen or prompt gluconeogenesis, all with the goal of maintaining a healthy amount of glucose in our bloodstream. When glucose in our blood drops too low, it can cause symptoms such as fatigue, shakiness, confusion, and sweating — this is our body trying to tell us it does not have enough energy.
On the other hand, when the glucose in our blood is too high, it can cause increased thirst and increased urination, as our body is trying to get rid of the extra glucose. Frequent glucose spikes can impact your sleep, energy, mood, focus, and more. If this happens chronically or stays elevated for too long, it can cause damage to our vessels resulting in inflammation, poor wound healing, and other complications such as damage to the kidneys and heart. (1)(5)
Insulin and glucagon work together to tightly regulate glucose. Insulin tends to be higher after you eat a meal, while glucagon is higher when you are fasting (like when you’re asleep). If insulin remains consistently high, it becomes hard for the body to utilise energy from our glucose stores because glucagon is being chronically suppressed.
A final note from Lingo
Glucose is essential for life. It is used to create energy that is required to keep us alive. The carbohydrates we eat are broken down into glucose to be used for energy. However, our body can also produce its own glucose through a process called gluconeogenesis. Carbohydrates include simple sugars (candy, soda, juice) and complex carbohydrates (vegetables, fruits, and legumes).
It is important to understand how glucose works in the body, especially since managing glucose has been associated with a reduced risk of chronic diseases (6)(7) as well as positively impacting aspects of our everyday life like our mood, energy levels, mental focus, sleep, and more (5).
Using a continuous glucose monitor like Lingo can give you real-time insights into your own glucose and seeing this data on has been shown to improve glucose control in just over a week. (8)