Examining the Evidence: Does Heating Milk Reduce Its Nutritional Value?

November 14, 2025 •

4 min read

A 2016 study found that boiling non-processed milk can reduce its calcium content by 10-14%. This highlights a common question: Does heating milk reduce its nutritional value? The answer depends on the temperature and duration of the heating process.

Quick Summary

Heating milk can degrade water-soluble vitamins like B-complex and C, denature whey proteins, and alter mineral balance, though pasteurization causes minimal loss. Excessive boiling leads to more significant nutrient depletion, impacting vitamin content more than macronutrients.

Key Points

Water-Soluble Vitamin Loss: Heating milk, especially boiling, can significantly deplete water-soluble vitamins such as B-complex and vitamin C.
Minimal Pasteurization Impact: Commercially pasteurized milk experiences only minimal nutrient loss due to its controlled, low-temperature, short-time heating process.
Whey Protein Denaturation: Heat causes whey protein to denature, or unfold, which can affect its structure and potentially alter digestibility for some individuals.
Minerals Retained: Essential minerals like calcium and phosphorus are not destroyed by heat, though their distribution in milk can change, which may slightly affect bioavailability.
Food Safety First: Heating raw, unpasteurized milk is a necessary process to kill harmful bacteria, and the safety benefits outweigh the moderate nutritional losses.
Use Mild Heating: To minimize nutrient loss when heating milk at home, use a lower temperature and avoid prolonged boiling.
Fat-Soluble Vitamins Stable: Vitamins A, D, E, and K are fat-soluble and largely resistant to heat degradation during typical milk processing.

Understanding Heat's Impact on Milk's Composition

Milk is a complex and nutritious liquid, rich in proteins, fats, carbohydrates, vitamins, and minerals. However, applying heat initiates chemical and physical changes that can alter its nutritional profile. While industrial processes like pasteurization are designed to minimize these effects, home boiling can have a more significant impact due to higher temperatures and longer durations. The key is understanding which components are heat-sensitive and by how much they are affected.

How Heating Affects Milk's Core Nutrients

Water-Soluble Vitamins (B-complex and C)

These vitamins are the most vulnerable to thermal degradation. Prolonged, high-heat exposure can cause substantial losses. For example, some studies show that boiling milk can reduce levels of B-vitamins by 25% or more, with folic acid potentially decreasing by as much as 36%. Vitamin C is also highly sensitive to both heat and light, though milk is not a primary source of this nutrient for most people. While these losses can be significant, pasteurized milk is often fortified with vitamins to compensate.

Proteins (Casein and Whey)

Milk contains two primary proteins: casein (approx. 80%) and whey (approx. 20%). Casein is relatively heat-stable, but whey protein is heat-sensitive and begins to denature (unfold) at temperatures above 60°C. While this alters its structure, it doesn't necessarily reduce the total protein content. In some cases, the denaturing process can make the protein easier to digest for certain individuals. However, excessive heating, as seen in ultra-high temperature (UHT) processing, can cause structural changes that result in a decrease in the body's ability to retain the protein.

Minerals (Calcium and Phosphorus)

Contrary to a common myth, boiling milk does not destroy its mineral content, but it can affect its bioavailability. Heating milk can shift the balance of minerals like calcium and phosphorus between the soluble and colloidal phases. This can result in the precipitation of calcium phosphate, especially at higher temperatures. While the total amount of calcium remains largely unchanged, its availability for absorption can be altered, though studies suggest this impact may be minimal.

Fats and Fat-Soluble Vitamins (A, D, E, K)

Fat-soluble vitamins (A, D, E, K) are considerably more stable than their water-soluble counterparts and are largely retained during typical heating processes like pasteurization. However, exposure to light during storage can degrade these vitamins. The overall fat content is generally stable, but some of the longer-chain fatty acids may be converted into shorter- and medium-chain fats during boiling, which some studies suggest could offer certain health benefits.

Lactose and Taste

Lactose, the natural sugar in milk, is heat-sensitive. Boiling can convert some lactose into lactulose, a sugar that is not digestible by humans. This change might be beneficial for individuals with lactose intolerance, making the milk easier to consume, though it doesn't solve the problem for everyone. Heating milk also triggers the Maillard reaction, a chemical reaction between proteins and sugars that can cause a slight darkening in color and a change in taste. Rapid or prolonged boiling can also cause scorching and curdling.

Pasteurization vs. Boiling: A Key Distinction


Feature	Raw Milk	Pasteurized Milk	Boiled Milk (Home)
Processing Temp	Untreated	63-72°C (briefly)	~100°C (longer duration)
Nutrient Retention	All nutrients intact	Retains most nutrients, especially if fortified	Loss of water-soluble vitamins (B, C)
Protein Integrity	Native structure maintained	Preserves most of the protein structure	Whey protein is denatured; digestibility may be altered
Mineral Availability	All minerals readily available	Minerals remain bioavailable	Mineral bioavailability can be altered slightly
Pathogen Risk	High risk of harmful bacteria	Significantly reduced risk	Pathogens are killed
Taste/Texture	Raw, creamy	Typically unchanged	Altered taste, texture (skin, scorching possible)

The Benefits and Drawbacks of Heating Milk

Benefits:

Food Safety: The most crucial benefit is the elimination of harmful bacteria in raw milk, preventing serious illnesses.
Improved Digestion: For some, the denaturing of whey protein and conversion of lactose can make milk easier to digest.
Extended Shelf-life: Heating kills spoilage organisms, extending the milk's freshness.

Drawbacks:

Nutrient Depletion: The loss of water-soluble vitamins is a clear negative consequence of prolonged high heat.
Altered Taste and Texture: Uncontrolled heating can result in a change in flavor and the formation of an unappealing skin.
Energy Consumption: Repeated or unnecessary boiling uses energy for a process that offers no additional safety benefit for commercially pasteurized milk.

Minimizing Nutrient Loss When Heating Milk

If you need to heat milk, you can take steps to minimize the loss of nutrients:

Use Low to Medium Heat: Heat the milk slowly rather than bringing it to a rapid boil.
Heat for a Shorter Time: Avoid prolonged boiling. Turn off the heat as soon as you see small bubbles forming around the edge of the pan.
Cover the Pot: This can help prevent some vitamin loss by limiting oxygen exposure.
Use an Opaque Container: If storing heated milk, an opaque container protects light-sensitive vitamins.
Microwave Cautiously: While fast, microwaving can create hot spots and may still affect nutrients. Gently warm and stir frequently.

Conclusion: The Final Verdict on Heated Milk's Nutrition

Does heating milk reduce its nutritional value? The answer is yes, especially with prolonged high-heat boiling. Water-soluble vitamins like B-complex and C are the most susceptible to this degradation. However, the impact is highly dependent on the heating method. Commercially pasteurized milk, which is designed for minimal nutrient impact and maximal safety, retains the vast majority of its nutritional value. For raw milk, the decision to heat is a tradeoff between nutrient loss and the paramount importance of killing potentially dangerous pathogens. If you are heating already-pasteurized milk for comfort or cooking, keeping the temperature low and the time short is the best way to preserve its nutrient content. For those seeking to maximize nutritional intake, consuming chilled, pasteurized milk is the optimal choice.

An extensive breakdown of the changes in milk components due to heat can be found at Healthline.

Frequently Asked Questions

No, boiling milk does not destroy calcium, which is a mineral and not sensitive to heat in the same way vitamins are. However, heating can cause some calcium phosphate to shift from a soluble to a colloidal form, potentially affecting its overall bioavailability, though the total amount of calcium remains the same.

Pasteurization causes only a slight, and from a health perspective, insignificant reduction in a few heat-sensitive vitamins, while preserving the overall nutritional value. In contrast, raw milk carries a high risk of containing dangerous bacteria that can cause severe illness. The safety benefits of pasteurization far outweigh the minimal nutrient changes.

The skin on boiling milk is a film of fat and denatured whey protein that rises to the surface. As water evaporates, the protein and fat concentration at the surface increases, forming a membrane. Stirring the milk while heating and allowing it to cool while stirring can prevent this.

For some individuals, especially those with mild sensitivities, heating milk might improve digestion. Heat denatures whey protein and converts some lactose into lactulose, potentially making it easier to digest. However, this is not guaranteed for everyone, particularly those with a significant milk protein allergy or lactose intolerance.

To minimize nutrient loss, heat milk slowly over low to medium heat. Avoid bringing it to a full, rolling boil for a prolonged period. Turn off the heat as soon as you see small bubbles forming at the edges of the pan. Gentle heating for a short duration is key.

The significance of vitamin losses depends on your diet and reliance on milk as a source. For heat-sensitive B vitamins like riboflavin and folic acid, the losses from boiling can be considerable. However, if your diet is varied and milk is not your only source of these nutrients, the impact may be less significant overall.

No, boiling commercially packaged and pasteurized milk does not make it safer, as it has already undergone a heat-treatment process to eliminate harmful bacteria. Re-boiling this milk is unnecessary and primarily leads to further depletion of its nutritional value.

UHT processing involves heating milk to very high temperatures for a few seconds to achieve sterilization. While this process effectively kills all bacteria and extends shelf life significantly, it causes more extensive degradation of heat-sensitive vitamins compared to standard pasteurization.