Dairy products are superfoods. They provide a variety of vitamins, minerals and other essential health-promoting compounds, including calcium, vitamin K2, B vitamins, protein, gut-supporting probiotics and healthy fats, such as pentadecanoic acid (C15:0), an odd-chain saturated fat that some researchers now consider an “essential” fatty acid with beneficial metabolic effects.
This nutrient-dense food supports overall health in a number of ways, and dairy consumption has been linked to:
- Reduction of the risks of cardiovascular diseases, strokes and hypertension.1,2
- Improves metabolic health and reduces the risk of type 2 diabetes3
- Reduced risk of tooth decay4 and better bone health5
- Improves gut health, as probiotics present in raw dairy products, raw cheese, and fermented dairy products like yogurt and kefir can help maintain a healthy gut microbiome.6
Understanding Dairy Sensitivity
Dairy intolerance and sensitivity are increasingly common problems affecting millions of people, leading many to avoid them altogether (leading to the loss of vital nutrients and health benefits).
But what if there was a way for those with dairy issues to still enjoy the superfood benefits of milk, cheese, and yogurt? It turns out the answer might lie in understanding the difference between the A1 and A2 variants of the beta-casein protein found in dairy products.
Dairy products contain two main types of protein: casein (which makes up about 80% of the total protein) and whey (about 20%).
Casein protein: benefits and variants
Of the two main protein fractions in milk, casein provides the most benefits. It has been shown to improve metabolism, protect against stress, and reduce tryptophan absorption.
According to Dr. Ray Peat, “the main protein in milk, casein, appears to have some direct anti-stress effects.” Specifically, research has found that casein may help prevent acute stress by protecting adrenal cortex activity and cortisol production.7
Casein may also influence tryptophan metabolic pathways, increasing its conversion to niacinamide (which is beneficial) and reducing the availability of free tryptophan in the body.8 Contrary to popular belief, serotonin is not the “happiness hormone” we so desire.
Within the casein fraction, there are several subtypes, including alpha casein, beta casein and kappa casein. Beta casein is the dominant form and accounts for about 40% of the total milk protein.
It is important to note that there are two main variants of beta-casein protein: A1 and A2. The difference between the two comes down to a single amino acid in the 209-amino acid sequence that makes up the beta-casein polypeptide chain. In the A1 variant, the amino acid at position 67 is histidine. In the A2 variant, it is proline.
Digestive impact of beta-casein A1 versus A2
It may seem like a minor change, but it can have important implications for how beta-casein is broken down during digestion. Proline, present in the A2 variant, creates a strong bond that makes it harder for the protein to be broken down at that location. Histidine, present in the A1 variant, forms a weaker bond, allowing beta-casein to be broken down more easily at that location.
When beta-casein A1 is broken down, it can release a peptide called beta-casomorphin-7 (BCM7). Some people may find it more difficult to digest and completely eliminate this BCM7 peptide, which can lead to gastrointestinal distress and other unwanted effects.
In contrast, A2 beta-casein is not broken down in a way that releases BCM7, which could make it easier for many people to digest. This is where the distinction between A1 and A2 becomes particularly relevant for those with dairy sensitivities.
A1 vs A2: Sources and research
So where do these different beta-casein variants come from? It depends largely on the breed of dairy animal.
The vast majority of commercially produced cow’s milk in many parts of the world contains more of the A1 beta-casein variant. This is because most modern dairy cow breeds, such as Holstein, Friesian and Jersey, naturally produce more A1 beta-casein.
On the other hand, dairy products from goats, sheep, buffalos and certain traditional cow breeds such as Guernsey and some Jersey breeds tend to contain only the A2 variant of beta-casein. Human breast milk also contains only the A2 form.
This means that people who have difficulty tolerating cow’s milk and traditional dairy products may do better with A2 dairy sources.
There is a growing body of research exploring the potential differences in terms of health and digestibility between A1 and A2 dairy products. Several studies have found that switching from regular cow’s milk (containing both A1 and A2 beta-casein) to milk containing only the A2 variant can lead to improvements in gastrointestinal symptoms and overall well-being.
For example, a 2017 randomized, double-blind, crossover study published in the European Journal of Clinical Nutrition looked at the effects of A1 versus A2 beta-casein on digestive symptoms. Researchers had 41 healthy adults consume milk containing either A1 or A2 beta-casein for two weeks, with a two-week rest period in between.9
The results showed that participants experienced significantly less abdominal pain, bloating, and constipation when consuming A2 milk compared to A1 milk. Interestingly, those who reported lactose intolerance also reported improved lactose tolerance when drinking A2 milk.
Another study published in 2019 in the Nutrition Journal examined the impact of A1 versus A2 beta-casein on gut inflammation. Researchers had 600 healthy adults consume either A1 or A2 milk for two weeks. They found that A2 milk produced a reduction in gut inflammation markers compared to A1 milk.10
Exploring dairy alternatives
A 2020 review article published in the journal Nutrients summarized the evidence on A1 vs A2 dairy and concluded that “consuming cow’s milk containing A2, rather than A1, results in improved overall gastrointestinal status and reduced milk-related intestinal discomfort.”11
The authors noted that the mechanism likely involves the formation of BCM7 from beta-casein A1, which “may be a significant contributor to the reported gastrointestinal symptoms associated with the consumption of conventional bovine milk.”
Importantly, research suggests that these benefits may extend beyond those with diagnosed lactose intolerance or other overt sensitivities to dairy products. Even people who do not experience obvious digestive discomfort from dairy products may find that A2 dairy products are better tolerated.
Of course, individual responses may vary. Not everyone with dairy issues may experience the same degree of relief by switching to A2 dairy products. Other factors, besides the distinction between A1 and A2 beta-casein, may also influence the digestibility of dairy products. For example, lactose intolerance, which originates from a deficiency of the enzyme lactase needed to break down lactose, is a well-known problem for many people.
However, addressing any underlying metabolic or gut health issues can also play a key role in improving dairy tolerance over time.
For example, lactose intolerance may improve over time as gut health and metabolic function are optimized. Research suggests that lactose intolerance may be related to conditions such as small intestinal bacterial overgrowth (SIBO), which can affect the body’s ability to properly digest lactose.12 By addressing these underlying imbalances, many people find they can gradually reintroduce dairy products into their diets.
Additionally, some people may have trouble digesting dairy products that contain microbial rennet, an alternative coagulant to traditional animal rennet used in cheesemaking. More than 90 percent of American cheese is made with this genetically modified version called FPC (fermentation-produced chymosin), manufactured by Pfizer.
There are two main concerns with FPC used in cheese making: 1) toxicity (since traces of genetically modified bacteria have been found in the enzymes).13 and 2) digestive problems (since cheese can now act as an allergen and cause an allergic reaction, digestive or respiratory problems).14). More information about this FPC can be found here.
So if you’ve previously had digestive problems or allergic reactions to cheese, it’s possible that the problem was the type of rennet and not the dairy product itself.
How to Find Your Ideal Source of Dairy Products
Dairy products are undoubtedly nutritional powerhouses that provide a wide variety of vitamins, minerals, proteins and other essential compounds that promote health. For many people, dairy products can and should be an important part of a balanced, nutrient-rich diet.
By understanding the difference between A1 and A2 casein and experimenting with different dairy sources, people with sensitivities can once again enjoy the benefits of superfoods from this food group.
Buying raw goat or sheep cheese can be a good start, as they are naturally A2. You can also visit www.realmilk.com to find a dairy farm near you – this handy website will connect you with local dairy farms. Be sure to ask how they raise their animals, what the animals eat, and whether they have been tested and verified to be A2A2.
And the excitement doesn’t end there: the team at Nourish Cooperative has been hard at work slowly expanding the signature Mercola Cheese Box—the highest quality cheese you can find, delivered right to your door. The delicious cheese varieties are made with 100% grass-fed, vaccine-free A2 milk and traditional animal rennet for maximum purity.
Join the waitlist here to get your hands on these irresistible artisanal A2s as we expand our selection as more small-scale cheesemakers join the project.
About the author
Ashley Armstrong is co-founder of Angel Acres Egg Co., which specializes in low-PUFA (polyunsaturated fat) eggs that ship to all 50 states (join the waitlist here), and Nourish Cooperative, which ships low-PUFA pork, beef, cheese, A2 dairy, and traditional sourdough to all 50 states. Waitlists will reopen soon.
