Is Lactose a Healthy Sugar? The Facts Revealed

December 7, 2025 •

3 min read

Lactose is the primary carbohydrate found in milk, accounting for up to 40% of whole cow's milk's calories. Many view it with suspicion, but emerging research indicates that lactose is not the same as added sugar and offers several unique health benefits, challenging conventional wisdom.

Quick Summary

This article explores the nutritional profile of lactose, differentiating it from processed sugars. It details how lactose supports calcium absorption, promotes beneficial gut bacteria, and possesses a lower glycemic index, while also addressing the digestive issues experienced by those with lactose intolerance.

Key Points

Not an Added Sugar: Lactose is a naturally occurring milk sugar with benefits, unlike refined sugars frequently added to foods.
Aids Mineral Absorption: It helps the body absorb calcium, magnesium, and zinc, which are crucial for bone health.
Acts as a Prebiotic: Undigested lactose ferments in the gut, promoting the growth of healthy bacteria.
Lowers Glycemic Impact: With a lower glycemic index than sucrose, lactose causes a slower rise in blood sugar.
Potential for Intolerance: Many adults lose the ability to digest lactose, leading to bloating, gas, and diarrhea from lactase deficiency.
Low Cariogenic Risk: It poses a lower risk for dental cavities compared to other sugars.
Manageable Intolerance: Fermented dairy and lactase supplements can help those with intolerance enjoy dairy's benefits with fewer symptoms.

What Exactly is Lactose?

Lactose is a disaccharide, meaning it is a sugar composed of two smaller sugar molecules: glucose and galactose. It is naturally present in milk and other dairy products, unlike sucrose (table sugar) which is often added to foods and beverages. Your body relies on an enzyme called lactase, produced in the small intestine, to break lactose down into its absorbable components. In many adults, the body's production of lactase declines, a condition known as lactase non-persistence, which can lead to digestive discomfort.

The Health Benefits of Lactose

Beyond simply providing energy, lactose offers several health advantages when properly digested.

1. Enhanced Mineral Absorption

*Lactose is proven to improve the absorption of essential minerals such as calcium, magnesium, and zinc. This is especially crucial for bone health and development, particularly in infants where lactose is a vital component of breast milk. Research suggests this benefit may extend into adulthood as well.

2. Prebiotic Effects and Gut Health

Undigested lactose that reaches the large intestine acts as a prebiotic, a type of fiber that stimulates the growth of beneficial gut bacteria like Bifidobacteria and Lactobacillus*. These bacteria ferment the lactose, producing short-chain fatty acids (SCFAs) that support gut barrier integrity and reduce inflammation. This prebiotic effect is most pronounced in lactase-deficient individuals, provided they consume moderate amounts of lactose.

3. Lower Glycemic Index

*Compared to simple sugars like glucose or sucrose, lactose has a lower glycemic index (GI), typically around 46. This means it leads to a slower, more gradual rise in blood sugar levels after consumption. This can help with satiety, potentially aiding in weight management by regulating the hunger hormone ghrelin.

4. Reduced Dental Caries Risk

*Lactose is significantly less cariogenic (cavity-causing) than other fermentable sugars. It produces less acid in the mouth, and at a slower rate, which reduces the risk of dental erosion and decay.

The Flip Side: Lactose Intolerance

The primary drawback of lactose is its indigestibility for a large portion of the adult population. In individuals with lactase deficiency, undigested lactose travels to the large intestine where it is fermented by bacteria. This process produces gases and attracts water, causing a range of uncomfortable gastrointestinal symptoms.

Common symptoms of lactose intolerance include:

Bloating and gas
Abdominal pain and cramps
Diarrhea or constipation
Nausea

Comparison: Lactose vs. Sucrose

To better understand why lactose is a different kind of sugar, it's helpful to compare it to sucrose, the most common type of added sugar.


Feature	Lactose (Milk Sugar)	Sucrose (Table Sugar)
Source	Naturally found in dairy products and breast milk.	Extracted from plants like sugarcane and beets; widely added to foods.
Composition	Disaccharide: one glucose + one galactose molecule.	Disaccharide: one glucose + one fructose molecule.
Digestion	Requires the enzyme lactase. Digestion can be incomplete in many adults.	Requires the enzyme sucrase. Usually digested completely.
Glycemic Index	Low GI (approx. 46), causing a slow blood sugar rise.	High GI (approx. 65), causing a rapid blood sugar spike.
Gut Health	Can act as a prebiotic, promoting beneficial bacteria growth.	Does not offer prebiotic benefits; high intake can harm gut health.
Cariogenic Potential	Low, making it less likely to cause dental decay.	High, contributing significantly to tooth decay.

Managing Lactose for Health

For those with lactose intolerance, it's possible to manage symptoms while still reaping some of dairy's nutritional benefits. Options include:

Consuming smaller quantities: Many can tolerate small amounts of lactose without symptoms.
Choosing low-lactose products: Aged cheeses (like cheddar and Parmesan) and yogurt with live cultures have significantly reduced lactose levels.
Taking lactase supplements: Over-the-counter lactase enzyme drops or tablets can be taken before consuming dairy to help with digestion.
Selecting lactose-free dairy alternatives: The market offers a wide range of lactose-free milks and products that contain added lactase to break down the sugar beforehand.

Conclusion: A Nuanced Perspective

So, is lactose a healthy sugar? The answer is nuanced. For those who produce sufficient lactase, it is a healthy, naturally occurring carbohydrate that aids mineral absorption and provides prebiotic benefits. For the large portion of the population that is lactase-deficient, it can cause uncomfortable symptoms, but fermented dairy and lactose-free options allow many to still enjoy dairy's nutritional offerings. Ultimately, lactose is a functional component of milk, not an empty calorie, and its effects depend on an individual's unique biology.

This article is for informational purposes only and is not medical advice. Always consult a healthcare professional for dietary recommendations.

Frequently Asked Questions

Lactose is a naturally occurring sugar found in milk, while 'regular' sugar (sucrose) is often added to foods. Lactose also has a lower glycemic index and promotes better mineral absorption, making it nutritionally distinct.

No, but lactase deficiency is very common, especially in people of Asian, African, and Hispanic descent. However, many people with low lactase can still tolerate small amounts of lactose without significant symptoms.

Yes, for both tolerant and intolerant individuals, some lactose can reach the large intestine and act as a prebiotic, feeding beneficial bacteria like Bifidobacteria and promoting a healthier gut microbiome.

Primary lactose intolerance occurs because the body's natural production of the lactase enzyme gradually decreases after infancy. This is a normal, genetically programmed process in many populations.

You can get calcium from many sources besides milk. These include low-lactose dairy products like aged cheese and yogurt, fortified plant-based milks, and non-dairy foods like leafy greens and tofu. Supplements may also be an option.

No, the lactose content varies. Aged cheeses contain very little lactose, and yogurt with live cultures often has less. Fluid milk and ice cream have higher concentrations.

Lactose-free milk is regular milk with the lactase enzyme added to break down the lactose. For lactose-tolerant people, there is no major nutritional difference. For lactose-intolerant people, it is a healthier choice as it prevents the uncomfortable digestive symptoms.