(P25-035-25) Dairy Intolerance in Transition From Old World to New World Milk - Is A1 β-casein Responsible?

Objectives: Old World cows produce milk with A2 β-casein (A2) with histidine at 67^th position, while a polymorphism in New World cows changed this to proline, creating A1 β-casein (A1). A1 digestion generates beta-casomorphin-7 (BCM-7), an inflammatory opioid peptide linked to digestive discomfort. We hypothesize that immigrants accustomed to A2 milk may develop dairy intolerance upon exposure to A1 milk, common in the United States (US). 

Our objective is to assess whether individuals raised on A2 milk adapt to A1 milk by examining changes in dairy intolerance symptoms after relocating to the US.

Methods: We developed a longitudinal study with five surveys to track dairy consumption and intolerance over a year. The Retrodemo Survey collected baseline data on dairy habits, including milk type (A1 or A2), consumption frequency, intolerance symptoms, demographics, family history, and US dairy experiences. Four Prospective Surveys, conducted every three months post-recruitment, tracked recent dairy consumption and symptom severity. Participants were categorized into three groups: US-raised (habitual A1 consumers), immigrants in the US >3 months, and recent immigrants ( < 3 months). Fisher’s Exact Test compared intolerance prevalence between A1 and A2 consumers in the >3 months group.

Results: Preliminary analysis of Retrodemo (n=255) and three Prospective surveys from this ongoing study is underway. Among recent immigrants (n=49), most consumed A2 milk before US immigration (fresh: 20%, commercial: 50%). US-raised individuals (n=94) and >3 months immigrants (n=112) reported higher A1 milk consumption (47%) than A2 milk (4%). Of 244 respondents, 24 reported dairy intolerance. A chi-square test showed a significant correlation between race and dairy intolerance (p=0.02*). Fisher’s Exact Test comparing dairy intolerance prevalence between A1 and A2 milk consumers with a small preliminary sample revealed no significant association (p=1).

Conclusions: This is the first study examining immigration and dairy intolerance. Further longitudinal analysis will explore adaptation to A1 milk, potentially suggesting microbiome and/or epigenetic changes influencing dairy intolerance.

Funding Sources: Gift funds from the A2 Milk Company.