What has glucose but not fructose? Understanding the Sugar Differences

October 15, 2025 •

4 min read

An estimated 30-40% of the world's population may suffer from fructose malabsorption, making it crucial to understand the distinct roles of different sugars in our diet. This guide explains what has glucose but not fructose and why differentiating between them is essential for nutritional health.

Quick Summary

Starches and certain processed ingredients like dextrose provide pure glucose, while milk and malt sugars also contain glucose without free fructose. These foods are important for individuals managing specific dietary needs related to sugar absorption.

Key Points

Starch is pure glucose: Complex carbohydrates like rice, potatoes, and bread are polymers of glucose that contain no free fructose, making them a primary source of glucose.
Dextrose is identical to glucose: This corn-derived sugar is pure glucose and can be used as a sweetener or rapid energy source without fructose.
Lactose and Maltose provide glucose: The sugars found in milk and malted grains, respectively, are disaccharides that break down to glucose and do not contain fructose.
Fructose is metabolized differently: Unlike glucose, which is used broadly for energy, fructose is mainly processed by the liver, and high consumption is linked to metabolic concerns.
Fructose-free sweeteners exist: Rice syrup and glucose syrup are popular alternatives to sweeteners containing fructose for individuals with fructose intolerance.
Dietary health depends on sugar type: Choosing between different sugars is crucial for managing conditions like fructose malabsorption or for achieving specific athletic performance goals.

The Core Differences: Glucose vs. Fructose

To understand what has glucose but not fructose?, it's essential to first distinguish between these two simple sugars, or monosaccharides. Glucose is the body's primary and most readily available source of energy, circulating in the blood and used by nearly every cell for fuel. Fructose, often called "fruit sugar," is metabolized differently and primarily in the liver. Unlike glucose, high consumption of free fructose has been linked to potential metabolic health risks.

The Role of Starch: Nature's Glucose Storage

Starch is a polysaccharide, meaning it's a complex carbohydrate made up of long chains of glucose molecules. When you consume starchy foods, your digestive system breaks these chains down into individual glucose molecules, which are then absorbed into the bloodstream. This process provides a steady release of energy and, most importantly, contains no free fructose.

Starch-Based Foods

Rice: A staple in many cuisines, rice is a primary source of starch.
Potatoes: From russets to sweet potatoes, all potatoes are packed with starch.
Pasta: Made from grain flours, pasta is another major source of glucose-only carbohydrates.
Bread: Many varieties of bread, especially those made from wheat or corn, are high in starch.
Corn: Corn, including cornmeal and cornstarch, is a concentrated source of glucose.
Legumes: Foods like lentils, chickpeas, and beans are starchy and provide glucose.
Oats: Oatmeal and other oat products are a good source of complex carbohydrates composed of glucose.

Sweeteners and Other Processed Sources

Some sweeteners and processed ingredients are also predominantly glucose-based, making them suitable for diets restricting fructose. These are often manufactured from starches like corn.

Dextrose: Chemically identical to glucose, dextrose is often derived from corn and is used as a sweetener in many processed foods and for quick energy replenishment. It is also available as a powder.
Glucose Syrup: This is a concentrated solution of glucose polymers derived from starch. Unlike high-fructose corn syrup, glucose syrup contains very little to no fructose.
Rice Syrup: Created from fermented rice, this sweetener primarily consists of glucose and maltose, with very low fructose content.

Milk and Malt Sugars

Other less-common sugars found in food also provide glucose without fructose.

Lactose: The natural sugar found in milk, lactose is a disaccharide made of glucose and galactose, not fructose.
Maltose: Also known as malt sugar, this disaccharide is composed of two glucose units. It is found in malted grains like barley malt and is used in brewing and baking.

Comparison: Glucose-Only vs. Glucose-and-Fructose Sources


Food/Sweetener	Primary Sugar Type	Presence of Glucose	Presence of Fructose	Notes
Starches (e.g., Potatoes, Rice)	Polysaccharide	Yes (Polymers)	No	Provides steady, slow-release energy.
Dextrose Powder	Monosaccharide	Yes (Pure Glucose)	No	Fast-absorbing sugar, often used in sports supplements.
Glucose Syrup	Polysaccharide/Oligosaccharide	Yes	No/Minimal	Used in confectionery and baking for sweetness and texture.
Lactose (Milk)	Disaccharide	Yes (with Galactose)	No	Found in dairy products; intolerance is common.
Maltose (Malt Sugar)	Disaccharide	Yes	No	Found in malt products and used in brewing.
Sucrose (Table Sugar)	Disaccharide	Yes (50%)	Yes (50%)	Breaks down into equal parts glucose and fructose.
High-Fructose Corn Syrup (HFCS)	Disaccharide/Monosaccharide	Yes	Yes (Higher %)	Contains more fructose than glucose and is found in many processed foods and sodas.
Fruit	Monosaccharide/Disaccharide	Yes	Yes (Varies)	Fruits contain varying levels of both glucose and fructose.
Honey	Monosaccharide/Disaccharide	Yes	Yes	A mix of glucose and fructose.

Dietary Considerations: When to Choose Glucose-Only Sources

People on a low-fructose diet, such as those with dietary fructose intolerance (fructose malabsorption), must carefully select their carbohydrate sources. Fructose malabsorption occurs when the small intestine struggles to absorb fructose effectively, leading to digestive issues like bloating, gas, and pain. For these individuals, a diet rich in glucose-only or low-fructose carbohydrates is beneficial. The presence of glucose can even assist in the absorption of small amounts of fructose in some cases. In such instances, dextrose is sometimes used to aid absorption or manage hypoglycemia.

For athletes, dextrose provides a rapid source of energy that is absorbed very quickly, without the potential metabolic stress associated with high fructose intake. For general health, opting for complex carbohydrate sources like whole grains and starchy vegetables is recommended for a sustained energy release and better blood sugar management.

Conclusion

In summary, many naturally occurring and processed foods provide glucose without the presence of fructose. Starchy vegetables, grains, legumes, and specific sugars like dextrose, lactose, and maltose are excellent examples. Understanding these distinctions is important for managing various health conditions, from dietary fructose intolerance to managing blood sugar levels. By making informed choices about carbohydrate sources, individuals can better manage their nutritional needs and overall well-being. Individuals with dietary concerns should consult a healthcare professional or registered dietitian for personalized advice.

Frequently Asked Questions

All starchy foods are made of glucose polymers and therefore contain glucose but no free fructose. Examples include rice, potatoes, bread, pasta, corn, oats, and legumes like chickpeas and lentils.

Yes, dextrose is chemically identical to glucose. It is a simple sugar, or monosaccharide, often derived commercially from corn starch. It is used in many processed foods and for medical or athletic purposes.

A person might need a diet with glucose but not fructose if they have dietary fructose intolerance (fructose malabsorption). For these individuals, fructose can cause significant digestive issues, and eliminating it can alleviate symptoms.

Most fruits contain a mix of both glucose and fructose, though the ratio varies depending on the type of fruit. For example, apples and pears have more fructose, while grapes and bananas have a more balanced ratio.

Yes, lactose is a disaccharide found in milk that is composed of glucose and galactose, not fructose. It is therefore a fructose-free source of glucose.

Glucose syrup is made from starch and contains primarily glucose. High-fructose corn syrup (HFCS) is created by an enzymatic process that converts some of the glucose into fructose, resulting in a product with significant fructose content.

Table sugar (sucrose) is a disaccharide made of equal parts glucose and fructose. While the glucose can aid in absorption, the presence of fructose can still be problematic for some individuals with fructose malabsorption. Tolerance levels vary widely.