Why Your Lactose Intolerance Might Actually Be a Milk Protein Problem

milk pouring out of a pitcher into a clear glass sitting on a wood board in a nature setting

Lactose intolerance is the inability to digest lactose, a type of sugar found in milk and other dairy products. Individuals who suffer from lactose intolerance do not produce sufficient quantities of the digestive enzyme lactase causing them to experience gas, bloating, and other issues when they consume dairy. However, recent scientific studies are casting doubt on lactose intolerance statistics, suggesting that a percentage of people with perceived lactose intolerance may actually be sensitive to a milk protein called A1 casein.

In this article you will learn:


Lactose Intolerant? Maybe Not!

Do you suffer from “intestinal distress” after drinking a glass of milk or eating a bowl of ice cream?

If so, you’ve probably assumed that you’re one of the millions of Americans classified as lactose intolerant.

But what if you actually weren’t lactose intolerant after all?

The Statistics Need Revision

A cursory internet search reveals that lactose intolerance affects more than half of all adults worldwide, but according to the NIH, “Many individuals who think they are lactose intolerant are not lactose malabsorbers.”

In other words, there are potentially huge numbers of people who suffer from GI distress after eating dairy who actually have NO ISSUES with digesting lactose!

But if it isn’t lactose that is causing the very real symptoms people are experiencing, what is?

In recent decades, the source of this non-lactose related dairy intolerance has been discovered and it has to do with a milk protein called casein.

A1 and A2 Casein

In addition to sugar and fat, milk also contains several different types of protein.

The muscle-building protein whey is familiar to many people, but the predominant type of protein found in milk is actually the lesser-known casein protein.

Typically marketed to bodybuilders as a slow-digesting, “time released” protein source, casein actually comes in two forms, “A1” and “A2”.

These two forms differ by just a single amino acid, so if you were to look at both molecules under a high powered microscope, you would see that where A1 has a histidine, A2 has a proline.

This difference may be small on a molecular level, but it has big implications for your health.

To make matters worse, the problematic casein protein is everywhere.

A1’s Origin Story

A2 casein is commonly found in heritage breeds of cattle such as the Guernseys and Jerseys, as well as in human breastmilk, but most milk sold on supermarket shelves today has the A1 casein protein.

So how did this come to be?

Hundreds of years ago in Europe, a type of dairy cow known as the Holstein was developed, and while it’s milk was not the best in terms of quality, it’s production was prodigious.

With the advent of industrialized food production, the Holstein became the breed of choice for the new the dairy industry that was being dominated by large corporations.

By 1985, over 90% of all dairy cows were Holsteins, but unbeknownst to dairy farmers at the time, the Holstein has a genetic mutation that causes it to produce the A1 casein variant.

In other words, the Holstein was the darling of the milk industry, but its milk contained a dark secret that has only recently been discovered.

The Issues with A1

Given that A1 casein is found in nearly all commercial dairy products, including milk, yogurt, ice cream, and cheese, it’s important to know what this protein does when it gets into the body.

When the A1 casein molecule is digested, a bio-active opioid peptide called beta-casomorphin-7 (BCM-7) is formed.

Classified as a “casomorphin”, BCM-7 is an opiate-like molecule that has the ability to bind to opiate receptors throughout the body.

In the gut, BCM-7 decreases gut motility, which allows food to linger in the digestive tract, causing bloating, gas, and constipation.

High levels of gut BCM-7 have also been associated with changes to the gut microbiome and increases in digestive tract inflammation.

Opioid receptors are not exclusive to the gut however, so if BCM-7 is absorbed into the blood stream, it can impact far-reaching tissues like the brain.

Studies suggest that BCM-7 binding on neural tissue can lead to problems in information processing, detoxification (methylation), increased oxidative stress, and increased pro-inflammatory markers .

Adults with fully formed and developed digestive systems tend to experience the effects of BCM-7 “locally”, that is to say in the gut itself. Children however have a more porous digestive tract, which allows higher levels of BCM-7 to be absorbed into the blood, leading them to experience the neurological effects more strongly.

While a link hasn’t been conclusively proven, exposure to high levels of A1 casein, and therefore BCM-7, has even been associated with the development of autism.

Avoiding A1

Due to growing awareness and increased consumer demand, A2 milk options are finally returning to store shelves.

Small-scale milk producers have discovered that they can turn a profit by using A2 heritage breeds like the Jersey and Guernsey, who’s milk, although not as great in quantity as the Holstein, is of far greater quality and better for making artisan cheeses and other dairy products.

There is even a brand of milk sold specifically as “A2” by a New Zealand based company called The A2 Milk Company.

Unconventional non-cow alternatives also exist in the form of goat’s milk, sheep’s milk, and even camel’s milk.


Historical precedent and scientific evidence suggests that A2 form of casein is the healthier option for humans, while the relatively new, and often industrially produced, A1 variety is a potential risk factor in dairy related GI distress and even neurological issues.

If you have been avoiding milk products due to a fear of lactose, you may find relief, and rediscover the joys of dairy, by switching to A2.

Go Beyond with Natural Force

Here at Natural Force, we support A2 dairy farmers by sourcing the milk for our Organic Whey Protein exclusively from grassfed Jersey cows.

They live in sunny California, are treated humanely, are not given any growth hormones or antibiotics, and graze on grass all year long.

This is a difference that can be tasted when you mix it into your favorite smoothie or shake and is that can be felt immediately when it digests smoothly.

To learn more about the Natural Force Organic Whey difference.

Editor’s Note: This article was originally posted September 2016 and has been completely revamped and updated for accuracy and comprehensiveness.

Also published on Medium.