Milk, Science, and Learning to Talk Like a Dietitian
Milk, Science, and Learning to Talk Like a Dietitian
If you had asked me a year ago what I knew about milk, I probably would have said it has calcium, it has protein, and some people are lactose intolerant. That was pretty much it. I grew up drinking it, I drank plenty of it as an athlete, and I never really thought twice about it.
That changed more recently when I started working with Orgain in September. They had just launched an A2 protein shake, and I kept hearing the term “A2” without really knowing what it meant. Now I’m working with the a2 Milk Company (full transparency!), and I’ve learned more about milk than I ever expected to.
The science behind it is really interesting. Stick with me.
Cow’s milk protein is made up of about 80% casein and 20% whey. Beta-casein makes up roughly a third of that casein, and it comes in different variants, the two most common being A1 and A2. What surprised me most is that they differ by just one amino acid (out of 200+!). At position 67 of the protein chain specifically, A2 beta-casein has a proline, while A1 has a histidine.
That one swap changes how the protein breaks down during digestion. In A2 beta-casein, the proline helps protect the nearby bond from being cut by digestive enzymes. In A1, the histidine makes that bond easier to break, which can release a peptide called beta-casomorphin-7, or BCM-7. BCM-7 is an opioid peptide, meaning it can bind to opioid receptors in the gut. Some research suggests this may slow GI transit and contribute to bloating, discomfort, and inflammation in certain people.
This is where it gets even more interesting: glutathione. Glutathione is often called the body’s “master antioxidant.” It’s a small molecule made from three amino acids (glutamate, cysteine, and glycine), and it helps protect our cells from oxidative stress and inflammation. The catch is that our bodies need enough cysteine to make it, since cysteine is the rate-limiting building block for glutathione synthesis. In lab studies, BCM-7 was shown to down regulate glutathione in human gut and neuronal cell lines by limiting how much cysteine the cells could take up. In other words, the peptide from A1 milk may get in the way of cells pulling in the cysteine they need to build glutathione.
Researchers then tested this in people. In a double-blind, randomized, controlled cross-over study, healthy participants drank two 250 mL servings of milk a day, either conventional milk with both A1 and A2 beta-casein or milk with only A2. Glutathione levels were significantly higher while participants drank A2-only milk, at about 4.01 nmol/mL compared with 1.99 nmol/mL with conventional milk. That’s a pretty exciting finding!
The history behind it is pretty cool too. Originally, cows produced only A2 beta-casein. The A1 variant is thought to have come from a natural genetic mutation in some European dairy herds thousands of years ago, and it spread as those breeds became popular. Today, breeds like Holsteins tend to carry more A1, while breeds like Guernseys and Jerseys tend to carry more A2. Through a genetic test, cows can be identified as A1/A1, A1/A2, or A2/A2 producers, and the A2-only cows can be kept separate so their milk is collected and processed on its own. Human, goat, and sheep milk also have an A2-type beta-casein.
As cool as all of this is, it’s just as important to be clear about what A2 milk isn’t. It still contains lactose, so it won’t fix true lactose intolerance. It still contains casein, so it isn’t safe for someone with a milk allergy. And while the research is promising, it’s still developing.
What I didn’t expect was how much this experience would teach me about communication. Working in the nutrition industry, I’ve seen how companies share information with healthcare professionals (HCPs) like dietitians, doctors, and nurses…and those professionals ask great questions! They want to see the research, understand the limitations, and know the information is backed by science, not just marketing. It’s shown me how important it is to lead with the evidence, be upfront about any unknowns, and adjust how we explain things depending on who we’re talking to. Explaining A2 milk to a patient might be “it’s a different type of milk protein that some people find easier on their stomach,” while explaining it to a physician means talking about amino acid sequences, BCM-7, glutathione, and study design. Both are necessary.
Overall, ao matter where we end up as dietitians, whether that’s clinical, outpatient, community, or industry, we’ll always be translating science for someone. Learning how to do that clearly and honestly is one of the biggest lessons I’m taking away from this year. I came into this year thinking I’d learn a lot about nutrition, and I did. I just didn’t expect a glass of milk to be what taught me how to talk like a dietitian.
-LI
Reference:
Deth R, Clarke A, Ni J, Trivedi M. Clinical evaluation of glutathione concentrations after consumption of milk containing different subtypes of β-casein: results from a randomized, cross-over clinical trial. Nutr J. 2016 Sep 29;15(1):82. doi: 10.1186/s12937-016-0201-x. PMID: 27680716; PMCID: PMC5041571.
Comments
Post a Comment