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Ask the Experts: Pasteurization and the Devil in the Milk

From time to time, we here at the offices (Well…”office,” singular. Well… two cubicles and a lamp…) of will get a question from a reader that we just can’t wrap our heads around. Sure, if the question relates to Battlestar Galactica (original and re-imagined), World of Warcraft, or how delicious cookies are, we’re all over it.

Q: How delicious are cookies?
A: Cookies are very delicious.

But beyond knowing the names of all the Thundercats, our knowledge base gets a little murky. That’s why we’re so glad we’re lucky enough to have a stable of expert authors, champing at the bit and rarin’ to go—with areas of expertise ranging from the US Constitution to composting to photovoltaics to urban gardening to wonky policy issues…and on and on.

This reader question about raw milk, milk pasteurization, and the A1 beta-casein protein came in from one of our Twitter friends. We ricocheted it over to Keith Woodford, author of Devil in the Milk: Illness, Health, and the Politics of A1 and A2 Milk, for his take on it.

I’m curious about whether pasteurization and homogenization has any impact on a person’s ability to process A1 beta-casein. I know that heat can change the structure of proteins, but don’t know enough about the science behind it to have any clue about whether or not raw milk might be healthier or safer in this particular respect.

Thanks very much,


Here’s Keith:


There is no obvious reason why homogenization should affect the way that A1 beta-casein is broken down on digestion. Homogenization affects the fat molecules and how they are held together, but should not affect protein digestion. That is the theory, but sometimes theory can be proven wrong when more evidence comes in.   With pasteurization the story is more complex.  This is because pasteurization involves heat treatment and anything  over about 48 degrees Centigrade has the potential to cause denaturation of the proteins.  This may affect the way protein is digested. Corran McLachlan had a paper published in the Journal Medical Hypotheses in 2001 (Vol. 56, pp. 262-272) where he linked the increasing incidence of heart disease during the early and mid parts of the 20th century to early methods of pasteurization. I discuss this in my book (pp. 70-71). The early methods of pasteurization involved moderate heat for extended periods (the Holder method). McLachlan presented evidence across countries and regions that heart disease increased in the years following the introduction of pasteurization.  He also suggested that as pasteurization subsequently changed to methods using higher temperatures but for shorter periods, the denaturation may have been less. According to McLachlan, this may explain why heart disease rates declined somewhat in the second half of the 20th century despite no  decrease in the ‘classical ‘ risk factors.  McLachlan linked the impact to the increased release from A1 beta-casein of the peptide beta-casomorphin-7 (BCM7, or what I call the milk devil’).  Personally, I consider this pasteurization evidence very interesting but far from conclusive.  For example, pasteurization led to greatly increased milk consumption, particularly in urban areas, so that may explain some of the apparent effect. And the data itself has some reliability issues.  I would like to see properly conducted trials, with no dairy industry involvement, in further testing this hypothesis linking various pasteurization methods to release of A1 beta-casein.  Even if there is a relationship, it is important to remember that we already know enough to say with great confidence that some BCM7 will still be released from raw milk unless the milk is A2. Also, if pasteurization does have an affect, then so will any other form of  heat treatment used, for example, in making ice cream and custards, or in the manufacture of muesli bars that are held together by casein.

Thanks, Keith!

Be sure to check out Keith Woodford’s new book, The Devil in the Milk: Illness, Health, and the Politics of A1 and A2 Milk.

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