Does Milk Alkaline or Acidic? A Scientific Look at Dairy pH

January 6, 2026 •

3 min read

Most people are surprised to learn that fresh cow's milk has a pH range of 6.5 to 6.8, which is slightly on the acidic side of the neutral pH 7. This fact often conflicts with the common perception that milk is a basic substance, a misconception fueled by its ability to temporarily soothe acid reflux.

Quick Summary

Milk is slightly acidic, not alkaline, with a fresh pH between 6.5 and 6.8. Its acidity increases over time as bacteria convert lactose into lactic acid, leading to spoilage and curdling. The pH level can also be influenced by the animal's health and milk processing.

Key Points

Fresh Milk is Slightly Acidic: Fresh cow's milk has a pH range of 6.5 to 6.8, which is slightly on the acidic side of the neutral pH of 7.
Acidity Increases with Spoilage: As milk spoils, naturally occurring bacteria ferment lactose into lactic acid, causing the pH to drop and the milk to become more acidic.
Lactic Acid Causes Curdling: The increased acidity from lactic acid eventually causes the milk's proteins to curdle, which occurs when the pH drops to approximately 4.5.
Factors Influence Milk pH: The pH of milk can be influenced by several factors, including the animal's health (e.g., mastitis increases pH) and processing methods (e.g., heat treatments).
Temporary Heartburn Relief: While milk is sometimes used for acid reflux, its soothing effect is temporary, as its high calcium content can stimulate more stomach acid production later.

Understanding the pH Scale

To determine if milk is alkaline or acidic, we must first understand the pH scale. The pH scale measures the concentration of hydrogen ions ($H^+$) in a solution, which determines its acidity or alkalinity. The scale runs from 0 to 14, where:

A pH below 7 is acidic.
A pH of 7 is neutral.
A pH above 7 is alkaline (or basic). Each full pH unit represents a tenfold increase or decrease in acidity, making even small shifts significant. For instance, a pH of 6 is ten times more acidic than a pH of 7.

The True pH of Fresh Milk

Contrary to popular belief, fresh cow's milk is not alkaline; it is slightly acidic. The typical pH of fresh milk falls within the 6.5 to 6.8 range. This value is very close to neutral, which explains why some might mistakenly consider it a neutral food. The slight acidity is a result of milk's natural composition, which includes proteins like casein, as well as phosphates and citrates.

Factors Affecting Milk's Initial pH

Several factors can cause slight variations in the pH of milk right after it's produced:

Cow's Diet and Breed: The diet of the cow and its specific breed can influence milk composition and, consequently, its pH.
Mastitis Infection: Milk from cows with mastitis, an infection of the mammary glands, often has a higher, more alkaline pH (sometimes reaching up to 7.5) due to the presence of blood components.
Colostrum Content: The first milk produced by a cow after giving birth, known as colostrum, is more acidic than regular milk.

How Milk Becomes More Acidic Over Time

Perhaps the most significant factor affecting milk's pH is time. As milk ages, it naturally sours and becomes more acidic. This process is driven by harmless Lactobacillus bacteria, which feed on lactose, the natural sugar in milk. Through a process of fermentation, these bacteria convert lactose into lactic acid. The buildup of lactic acid causes the pH to drop. As the pH decreases toward 4.5, the milk's proteins (casein) become unstable and coagulate, causing the milk to curdle. This is the tell-tale sign that milk has gone sour.

Milk Products and pH

Many dairy products are intentionally created by exploiting this acidification process. Here's how different products stack up:


Product	Typical pH Range	Process	Acidity Level
Fresh Cow's Milk	6.5–6.8	None (natural)	Slightly Acidic
Yogurt	4.0–4.6	Fermentation by bacteria	Moderately to Highly Acidic
Buttermilk	~4.5	Fermentation of milk	Moderately Acidic
Hard Cheese	4.4–5.3	Fermentation and aging	Moderately Acidic
Evaporated Milk	Slightly more acidic than fresh milk	Heat treatment	Slightly Acidic

Milk's Complex Role in Stomach Acidity

Despite being slightly acidic, milk is often used as a temporary remedy for heartburn and acid reflux. The soothing effect is primarily due to the physical properties of milk, not its pH. The fat in milk coats the esophagus, providing temporary relief from the burning sensation. However, this effect is short-lived. Milk also contains calcium, which is known to be alkaline. In the stomach, this calcium can trigger the production of more gastric acid, potentially worsening symptoms in the long run for individuals with conditions like ulcers. Cold milk may act as a short-term buffer, but it can interfere with proper digestion by diluting stomach acid, which is needed to break down food efficiently.

Conclusion

To definitively answer the question "Does milk alkaline or acidic?", the clear, science-backed answer is that fresh milk is slightly acidic, not alkaline. While its pH is very close to neutral, a proper reading will place it on the acidic side. The key to understanding its full chemical profile, however, lies in recognizing that milk's pH is dynamic. It begins slightly acidic and becomes progressively more so as it spoils, a process facilitated by lactic acid bacteria. The common misconception of milk as an alkaline remedy for heartburn overlooks the temporary nature of its soothing effect and the potential for increased stomach acid production later on. For reliable, long-term relief from acidity issues, consulting with a healthcare professional is always the best approach, rather than relying on milk.

Authoritative Source: For a deeper dive into the health implications and myths surrounding milk's acidity, you can refer to the detailed analysis provided by Healthline on the pH of milk and its effects on the body. https://www.healthline.com/health/ph-of-milk

Frequently Asked Questions

While cold milk can provide temporary relief from acid reflux by coating the esophagus, it is not a long-term solution. The calcium in milk can stimulate the stomach to produce more acid, potentially worsening symptoms later.

The pH of fresh cow's milk typically ranges between 6.5 and 6.8, making it slightly acidic but very close to neutral.

Milk turns sour because naturally present bacteria convert the milk sugar, lactose, into lactic acid. This process, known as fermentation, lowers the pH and increases the acidity of the milk.

Sour milk is more acidic than fresh milk. As bacteria produce lactic acid, the pH of the milk drops, indicating an increase in acidity.

Yes, processing methods can affect milk's pH. For example, some heat treatments can slightly increase acidity, while fermented products like yogurt have a much lower, more acidic pH.

Raw milk is generally slightly acidic, similar to pasteurized milk. Some sources suggest raw milk may be more alkaline-forming in the body after digestion, but this is a complex nutritional concept distinct from its actual pH.

The slight acidity of milk is due to its natural chemical composition, including proteins like casein, as well as mineral salts such as phosphates and citrates.