Does Lactose Have Any Benefit? Unpacking the Surprising Role of Milk Sugar

November 11, 2025 •

4 min read

A 2025 narrative review explored the broader biological functions of lactose, suggesting multiple physiological benefits beyond a simple energy source. So, does lactose have any benefit? For those who can digest it, this natural milk sugar supports gut health and enhances mineral absorption.

Quick Summary

Lactose offers benefits like enhanced mineral absorption, prebiotic effects for gut health, and a low glycemic index, depending on an individual's digestive capacity.

Key Points

Prebiotic Effect: Undigested lactose can serve as a prebiotic, fostering the growth of beneficial gut bacteria like Bifidobacterium and Lactobacillus.
Enhanced Mineral Absorption: Lactose boosts the intestinal absorption of minerals such as calcium and magnesium, an effect particularly pronounced and important in infants.
Low Glycemic Impact: With a low glycemic index, lactose provides a slower, more sustained release of energy compared to other common sugars.
Supports Infant Development: As the primary carbohydrate in breast milk, lactose is critical for providing energy and building blocks for the brain and nervous system in infants.
Less Harmful to Teeth: Lactose is less cariogenic than sugars like sucrose because oral bacteria ferment it more slowly, producing less acid.
Aids Athletic Performance: Moderate lactose intake during exercise can serve as an efficient fuel source, aiding glycogen resynthesis post-exercise.
Promotes Satiety: Its low glycemic index and potential influence on hunger hormones can contribute to a greater feeling of fullness.

The Multifaceted Role of Lactose

Beyond its fundamental role as an energy provider, lactose offers a range of additional health benefits, especially in infants and individuals with lactase non-persistence (LNP) who consume it in moderation. These benefits, however, are subject to an individual's digestive capacity, which varies due to genetic and epigenetic factors. Exploring these functions reveals why lactose is more complex than a simple carbohydrate.

Lactose as a Prebiotic

For individuals with LNP, or even in some lactose-tolerant people, some ingested lactose escapes digestion in the small intestine. It then travels to the large intestine where it is fermented by the colonic microbiota, effectively acting as a prebiotic. This fermentation process supports the growth of beneficial bacteria, such as Bifidobacterium and Lactobacillus. A balanced gut microbiome is vital for digestive, metabolic, and immune functions. The fermentation also produces short-chain fatty acids (SCFAs), which provide energy to intestinal cells and further promote gut health.

Enhanced Mineral Absorption

One of the most well-documented benefits of lactose, particularly in infants, is its ability to enhance the absorption of essential minerals like calcium, magnesium, and zinc. The hydrolysis of lactose creates a lower pH in the gastrointestinal tract, which increases the solubility of these minerals and aids their transport. While the evidence for this effect in healthy adults is conflicting, it is a key reason for lactose's inclusion in infant formula, where it mimics the composition of breast milk. For individuals with LNP, the prebiotic effect in the colon can also indirectly promote calcium absorption.

Sustained Energy Release and Satiety

Lactose has a low glycemic index (GI), approximately 46, which is significantly lower than sugars like glucose (GI 100) and sucrose (GI 68). The slow breakdown of lactose into glucose and galactose results in a more gradual release of energy and a less drastic rise in blood sugar levels. This effect contributes to prolonged satiety, making it advantageous for appetite and weight management. Some research also suggests that lactose may suppress the hunger hormone ghrelin more effectively than glucose.

Lower Cariogenic Potential

Unlike highly cariogenic sugars like sucrose, lactose exhibits a low potential for causing dental caries (tooth decay). This is because oral bacteria ferment it much more slowly, producing less acid in the mouth. The buffering capacity of milk itself also helps neutralize acidity, further reducing the risk of dental issues.

Supporting Athletic Performance

For athletes and active individuals, lactose can serve as an efficient fuel source. During prolonged exercise, it provides a mix of glucose and galactose that is readily metabolized. Post-exercise, this combination aids in the resynthesis of muscle and liver glycogen stores, supporting effective recovery. A 2025 review noted that moderate lactose intake during exercise is as efficiently metabolized as sucrose, while potentially sparing carbohydrate stores.

Lactose in Different Life Stages

Lactose plays different but important roles across the human lifespan, particularly due to the natural decline of the lactase enzyme after infancy in many people.

Infant Nutrition

For newborns, lactose is the main carbohydrate in breast milk, providing up to 50% of their energy needs. The galactose component of lactose is crucial for the synthesis of glycoproteins and glycolipids, which are essential for brain and central nervous system development. It also plays a key role in the colonization of a healthy gut microbiota in early life.

Adult and Elderly Nutrition

As lactase activity decreases with age in a large part of the global population, lactose digestion capacity varies. However, many individuals with LNP can still tolerate moderate amounts of lactose, and research suggests that long-term, low-dose consumption can improve tolerance. For those without intolerance, lactose contributes to nutrient-rich dairy products that are important for bone health and overall nutrition. In the elderly, where calcium absorption may be compromised, lactose's ability to enhance mineral absorption could be particularly beneficial.

Lactose vs. Other Sugars: A Comparison

To highlight lactose's unique properties, here is a comparison with other common sugars.


Feature	Lactose	Sucrose	Glucose
Source	Mammalian milk	Sugar cane, sugar beets	Many plant foods, also derived from starch
Sweetness	Low (approx. 20-40% of sucrose)	High (standard reference, 100%)	High (approx. 70-80% of sucrose)
Glycemic Index	Low (approx. 46)	Medium-High (approx. 68-92)	High (approx. 100-138)
Cariogenic Potential	Low	High	Medium-High
Metabolism	Slowly broken down into glucose and galactose	Rapidly broken down into glucose and fructose	Absorbed directly; rapid energy source
Special Benefit	Prebiotic effect and enhanced mineral absorption	None specific beyond energy	None specific beyond energy

Navigating Lactose Intolerance

Understanding the benefits of lactose is most relevant for those with some degree of lactase activity. However, even individuals with lactose intolerance can manage their symptoms while enjoying the nutritional advantages of dairy. Strategies include consuming smaller portions of dairy throughout the day, choosing fermented dairy products like yogurt and aged cheese that contain less lactose, or using lactose-free dairy products. The goal is to maximize the nutritional intake from dairy without experiencing discomfort. For those seeking guidance on managing symptoms, the NHS offers comprehensive information on lactose intolerance.

Conclusion

Far from being a simple, non-essential sugar, lactose provides several significant health benefits. From supporting infant brain development and calcium absorption to acting as a prebiotic for a healthy adult gut and providing a sustained energy source, its physiological functions are diverse and valuable. While lactose intolerance is a common consideration, it doesn't negate the benefits of lactose for those who can tolerate it, or the nutritional value of dairy products in general. As research continues to uncover its multifaceted roles, it becomes clear that for many, lactose is a valuable component of a healthy diet.

Frequently Asked Questions

Yes, for many individuals. When some lactose is not fully digested in the small intestine, it travels to the colon where it is fermented by beneficial bacteria. This process helps stimulate the growth of a healthy gut microbiome, acting as a prebiotic.

Yes, particularly in infants and potentially the elderly. In infants, it's known to enhance calcium absorption. However, its effect on calcium absorption in healthy, lactose-tolerant adults is still debated in scientific literature.

Yes, lactose has a lower glycemic index (GI) than sucrose (table sugar). This results in a slower, more gradual increase in blood sugar levels after consumption.

No, it's generally considered less harmful than other sugars like sucrose. Lactose is less cariogenic because oral bacteria ferment it more slowly, leading to lower acid production that can harm tooth enamel.

Lactose is the main carbohydrate in human milk and is a critical energy source, providing nearly 40% of a baby’s energy needs. It also aids in the absorption of calcium and is a building block for important molecules needed for brain development.

Yes, it is possible. Many people with lactose intolerance can still consume small to moderate amounts without major symptoms. Consuming fermented products like yogurt or hard cheeses, which have lower lactose content, is also a way to gain dairy nutrients. Additionally, moderate intake may have a prebiotic effect in the colon.

Yes. Due to its lower glycemic index and the slower release of energy, lactose can contribute to a prolonged feeling of fullness, which can be beneficial for managing appetite.

Not necessarily. While severe intolerance prevents most direct benefits, moderate intake may still provide prebiotic effects. The key is to manage symptoms while leveraging the nutritional value of dairy, possibly through fermented or lactose-free products.

Recent evidence suggests that moderate lactose intake can be an effective fuel source during exercise and can aid in glycogen resynthesis for post-exercise recovery.