Beginner's Guide: What Is Glucose?

ketogenicfasting
Jun 17
3 min read

Updated: 6 days ago

What Is Glucose?

Glucose is a simple sugar that serves as one of the body's primary sources of energy.

It belongs to the carbohydrate family and is the main sugar circulating in the bloodstream. For this reason, glucose is often referred to as blood sugar.

Many of the carbohydrates we eat are eventually broken down into glucose during digestion and absorbed into the bloodstream.

Why Is Glucose Important?

Every cell in the body requires energy to function. Glucose is one of the fuels the body uses to produce that energy.

Certain tissues, most notably red blood cells, depend entirely on glucose for energy. That's why the body must always maintain a minimum supply. When necessary, the body uses stored reserves to ensure these tissues receive the fuel they require at all times.

Where Does Glucose Come From?

Glucose occurs naturally in many foods, including:

Fruits
Vegetables
Honey
Milk
Legumes
Grains
Starchy foods

In addition to occurring naturally in food, glucose is commonly found in manufactured foods through "added sugars" used in products such as soft drinks, candies, desserts, breakfast cereals, and baked goods.

What Happens After Carbohydrates Are Consumed?

(1) As soon as carbohydrate-containing foods are consumed, they begin to be broken down into glucose.

(2) Within as little as 15 minutes, glucose begins entering the bloodstream and blood sugar starts rising.

(3) In response, the pancreas releases insulin.

(4) Think of insulin as a key that unlocks the cell's door (insulin receptor), allowing glucose to enter the cell.

(5) The cells use glucose as fuel. The challenge begins when more glucose keeps arriving than the cells can use.

(6) As blood sugar continues to rise, the pancreas releases more insulin in an effort to move more glucose into the cells.

(7) Over time, the cells become saturated with fuel and less responsive to insulin's signal.

When the cells no longer respond normally to insulin's attempts to move glucose into the cell, this condition is known as insulin resistance.

As blood sugar rises, more insulin is released. As more insulin is released, insulin resistance can worsen, creating a vicious cycle.

(8) When too much glucose keeps arriving too often through snacks, the next meal, and a little grazing in between, the excess must be stored somewhere.

Excess glucose is gradually converted into body fat and stored as an energy reserve.

Is Glucose Bad?

No. Glucose is essential for life. The body depends on glucose to perform many important functions, and certain tissues require a continuous supply of it.

The concern is not glucose itself. The concern is maintaining blood sugar within the healthy range. When way more glucose enters the bloodstream than the cells can take up, blood sugar remains elevated. The pancreas responds by releasing more insulin. Over time, persistently elevated blood sugar and insulin can cause a variety of health problems including insulin resistance.

Glucose and the Ketogenic Lifestyle

A ketogenic lifestyle limits carbohydrates, which reduces the amount of glucose entering the bloodstream from food.

As less glucose becomes available, the body gradually begins relying more heavily on fat and ketones for fuel.

The goal is not to eliminate glucose. The goal is to restrict the constant flood of glucose entering the bloodstream from the modern high-carbohydrate diet and shift more of the body's energy needs toward fat and ketones.

The Bottom Line

Glucose is a simple sugar and one of the body's primary energy sources (the other is the ketones).

In simple terms, glucose is not the enemy. On the contrary, it is a readily available fuel that can be used quickly or stored for later use. The challenge is the constant oversupply of glucose that results from a modern high-carbohydrate diet.

Most of the carbohydrates we eat are eventually converted into glucose during digestion. The fiber carbs move through the digestive tract largely intact.

The body carefully regulates glucose levels because certain tissues depend upon it at all times. Understanding glucose is an important first step toward understanding carbohydrates, blood sugar, insulin, and the ketogenic lifestyle.