Confessions of a Recipe Hoarder: Food Intolerance, Milk, and Genetic Variants in Proteins


Spring Hill Jersey Cheese

Are you tired, run-down, listless? Do you poop out at parties? The answer to all your problems may lie with the type of milk you are drinking.

Food intolerances in the United States are on the rise, and an increasing number of people are avoiding one of the biggest offenders: dairy. While many sufferers may assume the are lactose intolerant, new research suggests that the proteins found in milk produced by cattle, specifically Holstein cows, the most ubiquitous bovine in American commercial dairy production, may be culprit.

A1 and A2 beta-casein are genetic variants of the proteins found in cow’s milk and have different chemical structures, respectively. Each cow carries two copies of the gene in three different possible combinations: A1/A1, A1/A2, or A2/A2. These aren’t dominant or recessive genes like brown or blue eyes, meaning that if a cow produces both A1 and A2 beta-casein, the cow will produce them in equal amounts.

A2 beta-casein was present in cattle prior to domestication, but several thousand years ago a mutation occurred altering one amino acid in the protein chain, thus creating the A1 gene in some dairy herds. It is interesting to note that human breast milk contains exclusively A2 beta-casein, which may suggest that our bodies are not designed to digest A1 proteins. Goat and sheep’s milk also have exclusively A2 proteins and not all cows produce the A1 variant.

Sixty-five percent of Jersey cows and eighty percent of Guernsey cows produce A2/A2 milk. Many African and Asian breeds produce one hundred percent A2/A2 milk. The majority of Holsteins carry the A1 gene, and because A1 beta-casein cows produce larger quantities of milk, they are often preferred over other cows in commercial dairy production.

Ingredients + Dates for Dessert

So what are the health implications of eating dairy produced by A1 beta-casein cows? Normally, beta-casein is broken down during digestion, but because of the A1 mutation and the altered amino acid, the protein chain breaks and creates a peptide called BCM-7, which is an opioid, an oxidant, and causes inflammation. It is linked to serious diseases like type 1 diabetes, heart disease, and autoimmune disease and may cause allergies in some people if it travels through the bloodstream via a leaky gut.

Many farmers are phasing out A1 cattle in favor of A2, but the transition is lengthy and expensive.

More research is needed to form any conclusive answers, and consuming A1 milk may not present any harmful effects in healthy adults. Evidence suggests that infants may be most susceptible to the negative effects of consuming A1 dairy because of their immature gastrointestinal tracts, as are adults with leaky gut syndrome or who already have heart disease, diabetes, or autoimmune disease. There is no indication that eating A2 dairy is harmful, but it is more challenging to find in the U.S. Seek out small producers and farmers markets that have dairy vendors and opt for cow’s milk that is from Jersey, Guernsey, or Normandy cows or switch entirely to goat or sheep’s milk, which may be better tolerated.

The best advice is always: listen to your body and eat in moderation.

Swinburn B, 2004. Beta casein A1 and A2 in milk and human health. Report to New Zealand Food Safety Authority.

Cheese and Asparagus Frittata. Photo by Sharon Ona.

Cheese and Asparagus Frittata. Photo by Sharon Ona.

Cheese and Asparagus Frittata


  • 6 eggs
  • 1 bunch asparagus, washed and trimmed
  • 4 ounces shredded cheddar or chevre (I bought aged Jersey cheddar from my local farmers’ market)
  • Salt and pepper to taste
  • 1 medium shallot, minced
  • Scant ¼ cup chopped sun-dried tomatoes
  • 1 tablespoon butter (The butter I used was also Jersey organic and had the most amazingly fresh and creamy flavor)
  • 1 tablespoon olive oil


Preheat your oven to 375˚ Fahrenheit. Place the asparagus on a baking sheet and drizzle with olive oil and season with salt and pepper. Roast for 10 minutes, mixing once. Remove from the oven and let cool, then chop into ½-inch pieces.

In a large bowl, whisk your eggs, add salt and pepper, chopped tomatoes, asparagus, and grated or crumbled cheese.

In a large skillet, heat 1 tablespoon butter and sauté the shallot until translucent, about 5 minutes. Add the egg mixture and cook covered over medium heat for 5-8 minutes. Preheat your oven to the broil setting. Once the bottom of the frittata has set, place the pan into the oven and broil for 4 minutes, until lightly browned. If you do not have an oven-safe pan, flip the frittata onto a clean plate, then place back into the pan to continue cooking on the stovetop. Serve with mixed greens.


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