Ion Exchange vs. Cold Filtered Whey Protein: What's the Difference?
Eating the proper balance of macronutrients is key when it comes to gaining muscle, increasing strength, and dropping fat. Eat a diet rich in high quality protein sources, essential fatty acids (EFAs), fiber, vitamins, and minerals is essential for reaching every fitness goal.
Whey protein is considered the golden standard for those wanting a high concentration and high quality protein source at an affordable price. Whey is comprised of 8 key components: ß-lactoglobulin (ß-lg), -lactalbumin, bovine serum albumin (BSA), immunoglobulins (Ig), glycomacropeptide (GMP), lactoferrin (LF), lactoperoxidase (LP), and proteose Peptones (PP). 
However, not all whey protein is created equal - whey protein concentrate (WPC) typically has more fat, carbohydrates, and lactose compared to whey protein isolate (WPI). Furthermore, the manner in which the whey was extracted from milk is important.
This article will examine two popular methods for extracting the whey from dairy - ion exchange and cold filtration.
Ion Exchange Whey ProteinIon exchange is a method of isolating whey from milk using ion exchange resins, charge affinity, and mild pH adjustments. Ion exchange resins are polymers able to exchange specific ions within the polymer with ions in a solution that passes through the resin. 
Manufacturers alter the acidity or alkalinity (pH)of the solution to remove impurities and undesired materials. Synthetic resins are commonly used for ion exchange during the water purification process but it also occurs naturally in the Earth's soil and living cells. 
Manufacturers turn the surface charge attraction between the desired protein molecules and ion exchange resin on and off to isolate the desired elements. When an excess amount of undesired materials build up in the machine it's cleaned and the ion exchange process resumes.
Ion exchange offers the benefit of increased selectively in what is and is not filtered compared to cold-filtered whey protein. While ion exchange yields some of the highest concentrations protein per serving, there are a number concerns around using this filtration process. While it does increase protein concentration it decreases the subfraction glycomacropeptide (GMP) and increases the subfraction ß-lactoglobulin. 
While this may not sound like a concern GMP appears to offer numerous immune-protecting benefits while ß-lactoglobulin has been identified as the subfraction in milk causing the most allergic reactions in humans. 
Ion exchange filtration also uses strong acids and bases to adjust pH levels and resulting charge affinity.  While the pH doesn't significantly change it's worth noting that it temporarily alters the structure of the protein. Since ion exchange resins do not act as filters they do not remove bacteria or other microorganisms. 
If the resin is not cleaned or replaced regularly then serious contamination issues may occur.
Cold-Filtered Whey Protein
Cold filtration is a method of isolating whey from dairy based on molecular weight, size, and permeation properties in a cold processing environment.  Most cold filtrations undergo either microfiltration or ultrafiltration using a cross-flow or dead-end filtration stream.
Microfiltration uses a coarser filter compared to ultrafiltration and filters out particles larger than 0.1 microns (1x10-7m) and with a molecular weight larger than 100,000.  Microfiltration is a popular cost-effective filtration method for yielding high quality whey protein.
For those wanting the purest whey protein, look for products using ultrafiltration which filters out particles larger than 0.01 microns (1x10-8m) and with a molecular weight larger than 20,000.  This premium filtration techniques removes even more carbohydrates, fats, and lactose than microfiltration.
As expected, ultrafiltered whey protein typically carries a higher price tag. Both filtration methods involve the mechanical application of pressure to push the milk across the filtration membrane to yield whey protein.
Cross-flow filtration uses a permeate stream, which passes through the filtration membrane while the main stream is passing through the filtration membrane, to further isolate the undesired components.  Cross-flow filtration minimizes the undesired material build-up on the filtration membrane and removes more impurity than dead-end filtration.
Dead-end filtration is the process by which the main stream passes through the filtration membrane without a permeate stream.  Regardless of which filtration style you select ensure it's processed in a cold environment.
Exposure to temperature kills off immunoprotective components of whey as well as causes changes in the shape of the protein.  Cold-filtered whey protein contains a higher concentration of the aforementioned 8 key components and nutrients compared to whey proteins processed at high or even low temperatures.
Bottom LineBoth ion exchange and cold filtered whey protein can yield a high concentration of protein per serving. If you're looking for the absolute highest quality whey protein supplement, then the edge would go to cold-filtered whey protein. Filtration is slightly less selective than ion exchange because it isolates molecules based on a particular size rather than surface charge.
However, ion exchange significantly decreases the quantities of kappa-caseino glycomacropeptide (GMP) whereas cold filtration does not.  GMP demonstrates positive effects on the immune system as well protects against toxins (e.g. choler & E. coli), bacteria, and viruses. 
GMP's immunoprotective benefits suggest that eliminating this whey component from your diet would do much more harm than good. Luckily, cold filtered whey protein has much higher levels of naturally occurring GMP compared to ion exchange whey protein.
Now that you're armed with the difference between ion exchange and cold-filtered whey protein ensure you read the label on your protein tub before purchasing. The filtration process used to isolate the whey is just as important as the type of whey you purchase.
References1) Davisco Foods International, Inc. N.p., n.d. Web. 5 Nov. 2015.
2) Alchin, David, and Heather Wansbrough. "Ion Exchange Resins." New Zealand Institute of Chemistry. N.p., n.d.
3) Sélo, I., et al. "Allergy to Bovine Beta-lactoglobulin: Specificity of Human IgE to Tryptic Peptides." National Center for Biotechnology Information. Clin Exp Allergy, Aug. 1999.
4) "DOWEX Ion Exchange Resins - Fundamentals of Ion Exchange." Dow Liquid Separations. Dow Chemical Company, June 2000.
5) "Ultrafiltration, Nanofiltration, and Reverse Osmosis." Town of Hinesburg Vermont. Safe Drinking Water Foundation, 2013.
6) "How Crossflow Filtration Works." Pall Corporation. N.p., 2015.
7) Parag, H A, B Raboy, and R G Kulka. Effect of Heat Shock on Protein Degradation in Mammalian Cells: Involvement of the Ubiquitin System. The EMBO Journal 6.1 (1987): 5561.
8) Brody, E. P. "Biological Activities of Bovine Glycomacropeptide." National Center for Biotechnology Information. Br J Nutr, Nov. 2000.