什么是A2牛奶？酪蛋白变体指南
摘要
并非所有牛奶蛋白质都相同——乳制品中存在两种截然不同的casein蛋白变体，分别称为A1和A2。A1变体是基因突变的产物，可能引发消化问题，而A2变体则不存在同样的风险。选择来源于A2的乳制品，尤其是奶酪，可能会显著改善消化耐受性。
核心要点
- 酪蛋白约占牛奶蛋白质的30%，分为A1和A2两种形式
- A1酪蛋白是一种基因突变，而A2才是该蛋白质的自然原始形态
- A1变体会使一种名为BCM-7的化合物进入消化道，可能导致腹胀和Inflammation 炎症
- A2酪蛋白不会使BCM-7渗透进消化道，因此更易于消化
- 娟姗牛天然产出A2牛奶，是优选来源
- 山羊和绵羊乳制品本质上属于A2，其奶酪是安全且值得推荐的选择
- 若要食用乳制品，选择来源于A2的奶酪优于普通牛奶奶酪
详细说明
酪蛋白的两种类型
Casein蛋白约占牛奶总蛋白质的30%。酪蛋白内部存在两种结构变体——A1和A2——它们在amino acids的序列和排列方式上有所不同。这一看似微小的差异对消化过程会产生显著的连锁影响。
A1酪蛋白与BCM-7
A1变体被归类为基因突变——意味着它是随时间推移在某些牛品种的遗传基因中发生突然改变的产物。A1酪蛋白在消化过程中会释放一种名为**BCM-7（β-酪啡肽-7）**的肽段碎片。这种化合物能够穿越肠道屏障进入消化道，并可能引发：
- 腹胀
- 消化道Inflammation 炎症
- 一般性胃肠道不适
A2酪蛋白与消化耐受性
A2变体不会以使BCM-7侵入消化道的方式产生该物质。因此，对于食用普通乳制品会感到不适的人群来说，A2乳制品通常耐受性要好得多。许多自认为患有lactose intolerant的人，实际上可能是对A1酪蛋白产生反应，而非乳糖本身。
A2乳制品的最佳来源
| 来源 | A2状态 |
|---|---|
| 娟姗牛 | 天然A2 |
| 山羊 | 本质上为A2 |
| 绵羊 | 本质上为A2 |
| 标准荷斯坦奶牛 | 以A1为主 |
在选购奶酪时，请特别寻找经A2认证的产品。其中一个值得关注的品牌是Cascadia Creamery，该品牌专门生产来源于A2的奶酪。以山羊奶或绵羊奶制成的奶酪同样是可靠的A2选择，且在市面上广泛供应。
关于牛奶的总体建议
尽管本文重点在于帮助确实要食用乳制品的人做出更好的选择，但文中呈现的总体立场是不建议饮用液态牛奶。若要摄入乳制品，来源于A2的奶酪是更为推荐的形式。
相关概念
- casein
- amino acids
- Inflammation 炎症
- lactose intolerance
- digestive health
- dairy protein
- BCM-7
- genetic mutation
English Original 英文原文
What Is A2 Milk? A Guide to Casein Protein Variants
Summary
Not all milk proteins are the same — there are two distinct variants of casein protein found in dairy, known as A1 and A2. The A1 variant is the result of a genetic mutation and can cause digestive issues, while the A2 variant does not carry the same risks. Choosing A2-sourced dairy products, particularly cheese, may significantly improve digestive tolerance.
Key Takeaways
- Casein makes up about 30% of the protein in milk and comes in two forms: A1 and A2
- A1 casein is a genetic mutation, while A2 is the natural, original form of the protein
- The A1 variant allows a compound called BCM-7 to enter the digestive tract, potentially causing bloating and Inflammation 炎症
- A2 casein does not allow BCM-7 to penetrate the digestive tract, making it easier to digest
- Jersey cows naturally produce A2 milk, making them a preferred source
- Goat and sheep dairy are inherently A2, making their cheeses a safe and recommended option
- If consuming dairy, choosing A2-sourced cheese is preferable to standard cow’s milk cheese
Details
The Two Types of Casein
Casein protein accounts for roughly 30% of the total protein in milk. Within casein, there are two structural variants — A1 and A2 — that differ in the sequence and orientation of their amino acids. This seemingly small difference has significant downstream effects on digestion.
A1 Casein and BCM-7
The A1 variant is classified as a genetic mutation — meaning it arose from a sudden alteration in the genetics of certain cattle breeds over time. When A1 casein is digested, it releases a peptide fragment called BCM-7 (beta-casomorphin-7). This compound is capable of crossing the intestinal barrier and entering the digestive tract, where it can trigger:
- Bloating
- Digestive Inflammation 炎症
- General gastrointestinal discomfort
A2 Casein and Digestive Tolerance
The A2 variant does not produce BCM-7 in a way that allows it to invade the digestive tract. As a result, A2 dairy is generally far better tolerated by people who experience discomfort from conventional dairy products. Many individuals who believe they are lactose intolerant may actually be reacting to A1 casein rather than lactose itself.
Best Sources of A2 Dairy
| Source | A2 Status |
|---|---|
| Jersey cows | Naturally A2 |
| Goats | Inherently A2 |
| Sheep | Inherently A2 |
| Standard Holstein cows | Predominantly A1 |
When shopping for cheese, look specifically for A2-certified products. One brand mentioned is Cascadia Creamery, which produces cheese exclusively from A2 sources. Cheese made from goat’s milk or sheep’s milk is also a reliable A2 option and widely available.
General Recommendation on Milk
While the focus here is on making better choices if you consume dairy, the overall position presented is that liquid milk is not recommended. If dairy is consumed, cheese from A2 sources is the preferred format.
Mentioned Concepts
- casein
- amino acids
- Inflammation 炎症
- lactose intolerance
- digestive health
- dairy protein
- BCM-7
- genetic mutation