Since Joe Mercola has gone on a whey isolate-bashing drive (part of his materials promoting his whey protein concentrate line of products) I have been inundated with emails from my readers.

This is understandable since I have always encouraged my readers to sign up for Mercola’s newsletter as he is an excellent source of information (about 95% of the time). In fact, the only real contentions I have with him are over his probiotic blend, where he continues to list Lactobacillus sporogenes on the label, even though no such species exists.

And now with this whole “whey protein isolate is nasty and will damage your health” push. Again, most of what Mercola is saying is correct. However, he is failing to make a VERY important distinction between whey protein isolate that has been heat and/or acid extracted and whey protein isolate that has been cold, cross-flow membrane extracted.

Unfortunately, this distinction is the crux of the whey isolate issue! And it applies to all processing and extraction of milk products. As we know from raw milk literature – and the advice given to every breastfeeding mum – heat denatures milk proteins. Clear and simple. If you heat breastmilk (whether from a human, cow, goat, yak, or camel) the proteins are denatured, the live enzymes are killed and the beneficial bacteria destroyed.

Now, of course, there is no commercial whey protein supplement that can be sold which is made from unpasteurized milk – it is not legal in the U.S. or Canada – Mercola’s products included (see Mercola’s FAQ’s: “The raw milk is heated to 70˚C for a brief 15 seconds and then cooled down to 5˚C for the remaining processing.” – this is HTST pasteurization). So when we say that the proteins in certain whey products are denatured by heat, we are referring to high, prolonged heat – such as occurs during a heat-based extraction method. Likewise, when certain acids are used in the extraction process, they too can damage the milk proteins.

What Is Cross-Flow Membrane Extraction?

Passing a liquid through a membrane (filter) to extract (or remove) ingredients typically involves the liquid being poured into the filter – like when you drain spaghetti in a colander. This is called dead-end filtration.

With cross-flow membrane extraction, the liquid is flowed horizontally across the surface of the membrane (parallel to the membrane), which reduces the pressure involved in the process and reduces the likelihood of the retained material  plugging up the surface of the membrane. Here’s a diagram that explains the process clearly:

(Source: Membrane separations technology: principles and applications By Richard D. Noble, pg 6 )

Heat-Extracted Whey Isolate vs. Cold-Extracted Whey Isolate

This crucial distinction between heat-extracted whey and cold-extracted whey isolate becomes very apparent in a series of clinical studies conducted by researchers at McGill University in the 1980’s and then again in the 1990’s. They wanted to see which type of protein was best for stimulating immune function in mice. So they tested casein (a milk protein usually contained in whey concentrates), whey, soy, wheat, corn, egg white, fish, beef, spirulina and another algae called scenedesmus.

The first study in the 80’s revealed that whey protein provided the best immune-boosting activity by increasing the amount of glutathione available t