We know lactose, the sugar in milk, can cause gastrointestinal (GI) symptoms in those with lactose intolerance. A decline in the production of the digestive enzyme, lactase, that cleaves the 2 chain sugar, lactose, into its digestible sugar components of glucose and galactose, can lead to troubling GI symptoms such as gas, bloating, and diarrhea. Lactose intolerance is the most common food intolerance, globally.
But… can intolerance to dairy products exist beyond the sugar content (lactose) in cow’s milk? To be clear, I am not talking about a milk allergy (an immune mediated, potentially life threatening reaction) but rather an intolerance to other components in milk.
In my practice, working with many patients with digestive symptoms, I find that small subset of my clients exhibit food intolerance symptoms with the ingestion of any cow’s milk and cow’s milk products, even if they are lactose free. Most often these clients suffer with constipation or IBS-C and note symptom exacerbation with the consumption of any type of products made with cow’s milk.
So, I have started to delve a bit into the research. Years ago, I read that the protein, casein in cow’s milk may play a role in dairy intolerance. An 8 ounce glass of milk contains about 6-8 grams of casein, of which, 2-3 grams is beta-casein. Beta-casein can be present in two forms: A1 and A2. As cow’s became domesticated globally, the type of beta-casein they produced changed via a genetic mutation. Back in the day, cows only produced A2 beta-casein, but this has changed over time. In the US, most cow’s milk contains an even mix of A1 and A2 beta-casein. The protein component (amino acids) are arranged differently in A1 vs. A2 milk. Interestingly, human, sheep and goat milk have similar beta-casein protein chains to that of the A2 NOT A1. I wonder if this explains why some of my clients can tolerate goat’s milk better than dairy milk? (FYI: goat and sheep milk still have lactose!)
What’s the difference between A1 and A2 casein? A1 casein, when digested, produces a fragment called beta-casomorphin-7 (BCM-7). BCM-7 is associated with inflammation in the intestine and slowing down gastrointestinal transit time. It actually acts like an opioid, slugging gut movements. A2 casein, on the other hand, releases very little BCM-7.
For more scientific reading on this topic, click here. In animal studies, A1 beta casein was shown to increase the inflammatory marker myeloperoxidase (MPO) compared to milk containing A2 beta casein; Link here
So, I reached out to Bonnie Johnson, MS, RDN, Vice President Scientific Affairs & Activation The a2 Milk Company to learn more about the beta-casein in milk. The a2 Milk Company produces a milk product called a2 milk, that contains only the A2 beta casein. Here are a few of the questions I posed along with Bonnie’s answers:
Kate: Do you think everyone should be consider switching to A2 milk or is the benefit more for those with dairy intolerance or GI symptoms?
Bonnie: People who are already drinking milk, with no digestive symptoms, can keep drinking the same milk—there’s no reason to switch. However, because a2 Milk is ‘just milk’ it can be enjoyed by everyone in the household. There’s no reason to keep multiple “milks” on hand!
Kate: Can you discuss the potential effects of A1 milk —particularly on small bowel inflammation? Any impact on colonic inflammation?
Bonnie: When A1 protein is digested it releases a 7 amino acid fragment called BCM-7 that starts the inflammatory process high in the small intestine. Unrelated research suggests that when inflammation starts high up in the gut, the cascade of inflammatory particles may impact gastrointestinal tissue through the lower gastrointestinal tract too.
Kate: Any changes in the gut microbiome related to A1 vs. A2 milk?
Bonnie: Nothing specific as of now. However, it is a priority issue for The a2 Milk research platform.
Kate: When do you think A2 milk will be widely available nationwide?
Bonnie: It’s hard for me to speculate. As sales continue to grow in CA and demand for product grows across the country, we will move into more and more markets.
Kate: Is there any human studies looking at A1 milk in IBS or IBD specifically?
Bonnie: There is currently a study being conducted in Australia at Monash University that is looking specifically at the effects of A2 beta-casein protein on IBD.
No surprise… those smart scientists at Monash University, who developed the low FODMAP approach are right on top of this science and currently studying A2 beta-casein on inflammatory bowel disease!
A2 milk is available widely in California and spotty in other areas in the US. To see if A2 milk is near your home, click here.
Just last week, David Katz, MD wrote an article on A2 milk in Forbes. Check out this informative article here.
There is always something to learn, right?