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Opioids in Milk and Beef

Tuesday, February 28, 2017


Many are familiar with organic milk as a healthier alternative to industrial, nonorganic milk that has been accused of being laden with antibiotics and stress hormones. Organic milk is essentially antibiotic and hormone free and healthier, because the cows are fed grass or organically cultivated fodder. Still, it appears that the breed of cow may matter more than its feed.

All milk is a great source of calcium and protein, but today I’m going to talk about A1 beta-casein and A2 beta-casein cow milk and what difference each makes. Cows producing A1 milk include breeds such as Holstein, Friesian, British Shorthorn and Ayrshire that originated in northern Europe. Cows producing A2 milk include such dairy breeds as Guernsey, Jersey and beef cattle breeds, Charolais and Limousin that originated in the Channel Islands and Southern France.

The percentage of A1 and A2 beta-casein protein varies between herds of cattle and also between countries. Between 46 percent and 70 percent of Holsteins and Ayrshires, most commonly found in Europe (excluding France), the US, Australia and New Zealand, produce the A1 type beta-casein protein in their milk.

African and Asian cattle continue to produce only A2 beta-casein milk, and, on average, more than 70 percent of Guernsey and Jersey cows produce milk with predominantly A2 protein.

A2 cow milk comes from the older cattle breeds such as desi Indian cows or African cows that produce protein in their milk along with an amino acid called proline. In hybrid breeds, the proline amino acid mutated to histidine due to gene alteration, which scientists believe occurred thousands of years ago as cattle were being taken north into Europe. The proline at position 67 was replaced by histidine, with the mutation subsequently spreading widely throughout herds in the Western world through interbreeding.

A1 and A2 milk: What is the difference?

Nonorganic milk contains both A1 and A2 beta-casein, but A2 milk contains only A2 beta-casein. Our concern is an opioid present in A1 cow milk. When A1 beta-casein is digested, it releases a peptide (protein fragment of a short chain of amino acids) called beta-casomorphin-7 (BCM-7), which has seven amino acids in its peptide sequence and is also an opioid (narcotic) found in a high percentage of milk produced by A1 type cows.

BCM-7 is not active in A2 beta-casein. Proline (an α-amino acid) is strongly bonded to the small protein fragment BCM-7, preventing it from getting into the milk produced by A2 cows. On the other hand, histidine in A1 cows holds a weak bond with BCM-7, so it is easily released in the GI tract of animals and can enter the human body upon consumption of A1 milk and interact with the digestive system and internal organs.

While differences in A1 milk consumption can explain differences in heart disease and diabetes type 1 between countries, they do not explain why diabetes type 1 is increasing in almost all countries.

There appears to be a high degree of correlation between A1 beta-casein and heart disease and diabetes, which has raised the possibility that the type of casein in the fresh milk supply could possibly be a risk factor.

Interest in the distinction between A1 and A2 beta-casein proteins began in the early 1990s via epidemiological research and animal studies. Initially conducted by scientists in New Zealand, they found correlations between the prevalence of milk with A1 beta-casein proteins in some countries and the prevalence of various chronic diseases in those countries. The research generated interest in the media, among some in the scientific community and entrepreneurs. If it is indeed true that BCM-7 is harming humans, it would be an important public health issue as well as a commercial opportunity.

What does all this mean?

An emerging body of research suggests that many of the one in four Americans who exhibit symptoms of lactose intolerance could instead be unable to digest A1 beta-casein, most often found in milk from high-producing Holstein cows favored by American and some European industrial dairies. A vast number of observations indicate that many people who cannot digest A1 milk are able to digest A2 milk.

Surveys of A1 beta-casein consumption confirm the possibility that intensive dairy cattle breeding may have favored a genetic variant in milk with adverse effects in humans. Further animal research and clinical trials will be needed to compare disease risks of A1-free versus ordinary milk. More than 100 studies suggest links between the A1 protein and a range of health conditions—from heart disease to diabetes to autism—though evidence to date is far from conclusive.

Two observational studies have linked the consumption of A1 milk with an increased risk of heart disease. One experiment in rabbits showed that consuming A1 beta-casein promoted fat buildup in injured blood vessels. This buildup was much lower when the rabbits consumed A2 beta-casein.

Some theorize that peptides such as BCM-7 might play a role in the development of autism. One study of infants found higher levels of BCM-7 in those who were fed cow’s milk, compared to those who were breastfed. However, studies do not support all of the proposed mechanisms. BCM-7 was strongly associated with an impaired ability to plan and perform actions, and another study indicated that drinking cow’s milk may worsen behavioral symptoms in autistic children. Despite the suggested possibility, there is no conclusive evidence about the effects of A1 milk on autism, and the issue needs to be studied further.

Bottom line: Stay tuned. You’ll be reading more soon.

Spencer Thornton, MD