Understanding the Relative Scale: Which Type of Sugar Is Less Sweet?

November 13, 2025 •

3 min read

Lactose, the sugar naturally found in milk, is scientifically proven to be the least sweet of the common sugars, with a sweetness level of just 16% to 40% compared to sucrose. This fact answers the question: which type of sugar is less sweet?

Quick Summary

Lactose, or milk sugar, is the least sweet of all common caloric sugars. Other sugars, including glucose and maltose, are also less sweet than standard table sugar (sucrose). Sweetness is measured on a relative scale based on sucrose.

Key Points

Lactose is the least sweet: Found in milk, lactose has the lowest relative sweetness of common caloric sugars, at just 16-40% of sucrose.
Sweetness is relative to sucrose: Sucrose, or table sugar, is the standard benchmark used to measure the sweetness of other sugars, set at 100%.
Glucose is less sweet than sucrose: The body's main energy source, glucose (also known as dextrose), is only about 70-80% as sweet as table sugar.
Maltose is also less sweet: Used in grains and syrups, maltose is another sugar with a lower sweetness level compared to sucrose and fructose.
Fructose is the sweetest: In contrast to lactose, fructose (fruit sugar) is the sweetest of the common natural sugars, though its sweetness is temperature-dependent.
Concentration and temperature matter: The perceived sweetness of a sugar is not fixed and can be affected by its concentration and the temperature at which it is consumed.

The Science of Sweetness: A Relative Scale

For most people, the term "sugar" brings to mind the sweet taste of table sugar, or sucrose. However, this is just one of many types of sugar, each with its own unique level of sweetness. The sweetness of different sugars is measured on a relative scale, using sucrose as the benchmark, which is set at 100%. This allows for a clear comparison of how sweet one sugar is compared to another. The varying sweetness levels are due to the different chemical structures of each sugar molecule, which determines how strongly they interact with the sweetness receptors on the tongue. Factors like concentration, temperature, and pH can also influence the perception of sweetness.

Monosaccharides vs. Disaccharides

Sugars are categorized based on their molecular structure. Monosaccharides, or simple sugars, consist of a single sugar molecule, while disaccharides are formed by two linked monosaccharides. Their structure plays a significant role in their sweetness profile.

Monosaccharides: These are the building blocks of other carbohydrates. Fructose is a monosaccharide, known for being the sweetest natural sugar, sometimes up to 1.7 times sweeter than sucrose. Glucose, another key monosaccharide, is less sweet than sucrose.
Disaccharides: These are composed of two monosaccharide units. Sucrose is a disaccharide of one glucose and one fructose molecule. Lactose is a disaccharide of one glucose and one galactose molecule. The combination of these building blocks results in a different overall sweetness.

The Least Sweet Sugars

While fructose is often cited as the sweetest natural sugar, several other common sugars are significantly less sweet than table sugar. For those seeking to reduce perceived sweetness, these options are important to understand.

Lactose: The Least Sweet of All

Lactose, commonly known as milk sugar, holds the title for the least sweet of the main caloric sugars. It is a disaccharide found in dairy products and has a sweetness relative to sucrose ranging from just 16% to 40%. This is why milk and many dairy products are not overwhelmingly sweet despite containing sugar. Many adults are lactose intolerant due to a deficiency in the lactase enzyme, which is needed to break down lactose into its constituent parts for digestion.

Other Less Sweet Sugars

Several other sugars also rank lower than sucrose on the relative sweetness scale:

Glucose (Dextrose): This is the body's primary energy source and is often added to processed foods. Glucose is about 70-80% as sweet as sucrose, making it a noticeably less sweet alternative to table sugar.
Maltose: Formed during the breakdown of starch, maltose is found in grains and some beer. It is less sweet than sucrose, glucose, and fructose, with a relative sweetness of 40-50%.
Galactose: This monosaccharide is less sweet than glucose and is a component of lactose.

Sweetness Comparison Table

To provide a clearer picture, here is a comparison of common sugars based on their average relative sweetness to sucrose (which is set at 100):


Type of Sugar	Classification	Relative Sweetness (approx.)
Fructose	Monosaccharide	110-170%
Sucrose	Disaccharide	100% (Benchmark)
Glucose (Dextrose)	Monosaccharide	70-80%
Maltose	Disaccharide	40-50%
Galactose	Monosaccharide	60%
Lactose	Disaccharide	16-40%

Factors Affecting Sweetness Perception

Sweetness is not just about the sugar type; other factors can change the taste experience.

Temperature: Fructose, the sweetest natural sugar, is sweetest when cold and its sweetness diminishes with increasing temperature. This is why cold beverages with high-fructose corn syrup can taste sweeter than a hot food with the same amount.
Concentration: The relative sweetness of sugars can vary depending on the concentration in a solution. As concentration increases, the perception of sweetness doesn't always scale linearly.
Acidity: In some cases, high acidity can mask or mitigate the perceived sweetness of a sugar.

Conclusion: Choosing the Right Sugar

For those who prefer a less pronounced sweetness, understanding the relative sweetness of different sugars is key. Lactose is the clear winner for the least sweet caloric sugar, making it ideal for certain dairy applications or for reducing overall sweetness. Glucose and maltose are other viable options for tempering sweetness compared to sucrose. Ultimately, the choice depends on your specific dietary needs and desired flavor profile. By considering these different types of sugar, you can make more informed decisions about how to sweeten your food and drinks.

For further reading on the science behind sweetness, the review 'Sweetness - an overview' by ScienceDirect provides extensive information.

Frequently Asked Questions

Among the common caloric sugars, lactose, or milk sugar, is the least sweet, with a relative sweetness of about 16% to 40% compared to sucrose.

No, glucose (dextrose) is less sweet than sucrose. Sucrose is used as the reference point for sweetness (100%), while glucose is rated at about 70% to 80% as sweet.

No, brown sugar is not significantly less sweet than white sugar. Brown sugar is simply white sugar with added molasses, which does not substantially alter the overall sweetness level on a weight-for-weight basis.

The specific chemical structure of the lactose molecule determines how it interacts with the taste receptors on the tongue, resulting in a less intense sweetness perception compared to other sugars.

Relative sweetness is measured by comparing a sugar's taste intensity to a standard reference, which is usually a sucrose solution. Trained human taste panels are used to determine the concentration of a new sweetener that is equally as sweet as a known concentration of sucrose.

Yes, temperature can affect the perception of sweetness. Fructose, for example, is perceived as sweeter at cooler temperatures and less sweet when warm.

Yes, maltose is less sweet than glucose. While glucose has a relative sweetness of 70-80% compared to sucrose, maltose is rated lower at 40-50%.