What is A2 vitamin, and how does it differ from A2 milk?

First identified by a chemist in 1941, A2 vitamin, or dehydroretinol, is a less common subcategory of vitamin A found predominantly in the livers of freshwater fish. It is often mistakenly conflated with A2 milk, which refers to a specific type of dairy protein, not a vitamin.

Quick Summary

This article clarifies the distinction between A2 vitamin (dehydroretinol), a form of vitamin A, and A2 milk, which contains a specific beta-casein protein. It covers their origins, functions, and key differences.

Key Points

• A2 vs. A1: A2 vitamin is dehydroretinol, a form of Vitamin A, while A2 milk refers to a specific beta-casein protein, distinct from the A1 protein found in most conventional milk.

• Less Active Nutrient: As a nutrient, vitamin A2 (dehydroretinol) is less active in mammals than the more common vitamin A1 (retinol).

• Common Digestion Issues: The market for A2 milk is driven by reports that the A1 beta-casein protein can release a peptide (BCM-7) that may cause digestive discomfort for some individuals.

• Not for Allergies or Intolerance: A2 milk still contains lactose and milk proteins. It is not suitable for people with a milk protein allergy or lactose intolerance.

• Multiple Vitamin A Forms: The broader category of Vitamin A includes active retinoids (like retinol and dehydroretinol) and provitamin A carotenoids (like beta-carotene).

• Misleading Marketing: Claims surrounding A2 milk should be viewed critically, as marketing often emphasizes potential benefits that are based on limited research.

• Diverse Dietary Sources: For comprehensive vitamin A intake, a varied diet is key, including animal-based retinoids and plant-based carotenoids.

The Real A2 Vitamin: Dehydroretinol

Vitamin A is a crucial group of fat-soluble compounds that support vision, immune function, and skin health. The term “A2 vitamin” refers specifically to dehydroretinol, a naturally occurring, less active variant of vitamin A, also known as retinol. Discovered in the early 1940s, dehydroretinol was initially isolated from the liver of freshwater fish, where it is found in higher concentrations.

For humans and other mammals, the primary active form of vitamin A is retinol (or A1). The body can convert A1 to A2 through enzymatic processes, and human skin naturally contains the alcohol form of vitamin A2. However, the role and bioavailability of A2 vitamin in human nutrition are less significant compared to retinol and provitamin A carotenoids, like beta-carotene.

The Common Confusion: A2 Milk vs. A2 Vitamin

The most widespread confusion surrounding the term “A2” relates not to a vitamin, but to A2 milk. A2 milk is a dairy product that contains only the A2 variant of the beta-casein protein, as opposed to conventional milk, which is a mix of both A1 and A2 beta-casein. This distinction is driven by consumer interest in dairy alternatives for those with digestive sensitivities, and has no relationship to vitamin A.

The key difference lies in the protein structure. When digested, the A1 beta-casein protein can release a peptide called beta-casomorphin-7 (BCM-7). Some studies suggest this peptide may cause digestive discomfort in a subset of people, leading to symptoms often mistaken for lactose intolerance. In contrast, the A2 beta-casein protein does not release BCM-7 in the same way, which is why many who experience discomfort from regular milk report fewer issues with A2 milk. It is crucial to remember that A2 milk still contains lactose and is not a solution for individuals with a true lactose intolerance or dairy allergy.

Comparison: A1 Milk vs. A2 Milk

Feature	A1 Milk	A2 Milk
Protein Variant	Contains both A1 and A2 beta-casein.	Contains only A2 beta-casein.
Digestion	Can release the peptide BCM-7, potentially causing digestive discomfort.	Releases minimal or no BCM-7, leading to easier digestion for some sensitive individuals.
Inflammation	Some preliminary research links BCM-7 with inflammatory processes.	May cause a lower inflammatory response compared to A1 milk.
Health Concerns	Observational studies have raised questions about links to various health issues, though a direct cause-and-effect relationship is not established.	Often marketed as a gentler, more easily digestible option, though it is not a cure-all.
Market	Standard, conventional dairy product, widely available.	Niche market product, often at a higher price point.

Forms and Functions of Vitamin A

To fully understand the difference, it's helpful to review the various forms of vitamin A and their roles. As a fat-soluble nutrient, vitamin A is not a single compound but a group of related substances.

• Retinoids (Preformed Vitamin A): These are the active forms of vitamin A, found primarily in animal products.
  • Retinol (A1): The most common and active form of vitamin A in mammals, crucial for vision, immune health, and reproduction.
  • Retinal: An aldehyde form of vitamin A important for retinal pigments.
  • Retinoic Acid: Plays a vital role in cell differentiation and development.
  • Dehydroretinol (A2): Found in some species, particularly freshwater fish, and is less active in mammals.
• Provitamin A Carotenoids: These are plant-based pigments that the body can convert into vitamin A.
  • Beta-carotene: The most common provitamin A carotenoid, responsible for the orange color in carrots and sweet potatoes.
  • Alpha-carotene & Beta-cryptoxanthin: Other carotenoids with vitamin A activity.

Conclusion

In summary, A2 vitamin is a genuine but less common form of vitamin A, known scientifically as dehydroretinol and found mainly in freshwater fish. The common term “A2 milk,” however, refers to a specific dairy product containing only the A2 beta-casein protein, which some people find easier to digest than the A1 protein in regular milk. This distinction highlights the importance of understanding the specific biochemical differences behind nutritional terms and avoiding confusion between proteins and vitamins.

For more detailed information on vitamin A, consult resources from the National Institutes of Health. NIH Fact Sheet on Vitamin A

Frequently Asked Questions

Is A2 vitamin the same as A2 milk?

No, they are not the same. A2 vitamin is dehydroretinol, a specific form of vitamin A. A2 milk is a dairy product containing a specific type of beta-casein protein, not a vitamin.

What is A2 vitamin (dehydroretinol) used for?

A2 vitamin, like other forms of vitamin A, supports vision and overall health, but it is a less active form than retinol (A1) in mammals. Its primary sources are naturally occurring in freshwater fish.

Why do some people prefer A2 milk over regular milk?

Some people find A2 milk easier to digest because it contains only the A2 beta-casein protein. Regular milk contains A1 protein, which, during digestion, can produce a peptide called BCM-7 that may cause digestive issues in some individuals.

Can A2 milk help with lactose intolerance?

No, A2 milk is not a solution for lactose intolerance. It contains the same amount of lactose as regular milk. The digestive benefits some people report are related to the A2 protein structure, not the lactose content.

Is A2 milk better for you from a nutritional standpoint?

From a core nutrient perspective, A2 milk is generally comparable to regular milk. It contains the same vitamins and minerals. The primary difference is how the beta-casein protein is processed in the gut, which may offer digestive relief for some.

What are the main forms of vitamin A?

Vitamin A exists in two main forms: retinoids (preformed vitamin A) found in animal sources, and provitamin A carotenoids found in plant sources. The body can convert carotenoids into vitamin A.

Where can I find dietary sources of vitamin A?

Excellent sources of vitamin A include animal liver, eggs, and fortified dairy products (retinoids). Plant-based sources (carotenoids) include carrots, sweet potatoes, spinach, and other dark-colored vegetables and fruits.