Monday, August 13, 2012

Mutant Milk!? New Research Fuels the Flames on Hushed Up Concerns About Ill Health Effects of Homogenized Milk

Image 1: Wolverine could be the only face of the "Got Milk" campaign who does not have to care about potential negative health effects of homogenized milk.
In view of the fact that even the Wikipedia article on milk mentions the long-touted hypothesis that the release of the  membrane bound (bovine) xanthine oxidase during the homogenization process and it's potential to generate reactive oxygen specimen could pose a serious health risk, it's quite funny that none of the multitude of papers on the pro- or anti-atheriogenic effects of milk ever mentions mentions the issue of homogenization.

Now even if we discard the potential negative effects of BXO, the results of a recently published paper from the Center of Specialized Nutrition in the Netherlands would still suggest that milk does at least lose some of it's beneficial health effects in the course of the homogenization process (Oosting. 2012).

Large and fluffy or small? That does ring a bell, doesn't it? 

In their experiments the Dutch scientists fed mice infant formulas with either small or large phospholipid coated lipid droplets. Probably to the utmost satisfaction of Danone, the producer of the large lipid droplet formula (Nuturis) and sponsor of the study, the mice who received the regular formula with small lipid droplets were fatter and had compromised lipid and blood glucose levels (see figure 1), as well as pathologically increased leptin levels (not shown in figure 1).

Figure 1: It may remind you of comparing apples and oranges, but let's be honest, if it were not for the disruption of the large fat globules during the homogenization process, similarly large phospholipids as those Danone plans to unleash onto our children would be present in milk, anyway.
Irrespective of the funding and product pimping, the results of this study could have major implications that reach way beyond infant formulas and parenteral nutrition. After all, homogenized milk is common used in all sorts of milk based or milk-containing products. It's shelf stable and above all highly standardized and easily processable by the dairy and food industry, who are still spending truckloads of money to find means to further reduce the unwanted clumping that's so characteristic for the naturally occurring large fat molecules most of the end-consumer don't want to float on top of their heated milk either.

So, if the bovine xanthine oxidase that's released during the homogenization process does not, as Ho & Clifford and other researchers argued in the late 1970s (Ho. 1977), pose a risk for heart disease, what about the structural changes in the lipid fraction of milk? Do we know anything about these at all and could they be the underlying cause of the increase in allergies, diabetes risk that have never been convincingly attributed to milk consumption in general or whole milk consumption in particular? Did we focus to much on the quantity and type of fat in the milk and overlooked its structural organization?

Though shalt not fix something that ain't broken!

In a 2007 review of the literature on the potential impact homogenized milk could have on our health, Mikalski discusses exactly this question: What's the physiological consequence of the physical "rupture of fat globules" which occurs during the heating and homogenization process and "creates a new interface" on the membrane of the fat globules so that "other surface active components" (Mikalski. 2007) will more or less randomly adsorb to the remnants and form a new structurally different membrane.
Figure 2: After the homogenization process took place none of the original functional large fat globules is left, smaller ruptured globules have taken their place and are used by other molecules as a "Trojan horse" (left), distribution of milk fat globule sizes in different types of whole milk - open circles - raw whole milk, full circles - whole milk homogenized at 5MPa, open squares - whole milk homogenized at 10 MPa, full squares - whole milk homogenized at 50MPa (partly adapted from Mikalski. 2007)
Unfortunately, the #1 compound that will bind to the now the disrupted surface structures of the molecules in the homogenized monster milk are casein micelles (Zahar. 1996). Yep, exactly those molecules, of which some scientists, though most of them discard the hypothesis that homogenized milk is not at least as good for you as regular milk, still speculate that they could be responsible for many if not all of the aforementioned negative health effects of milk (Kohno. 1994; Laugesen. 2003; Tailford. 2003).

Homogenized, fat reduced zombie milk?

Figure 3: Distribution of milk lipids in globule core, membrane and skim phase (top, based on Michalski. 2007) and electron micrographs at 15× and 100× augmentations of (A) raw, (B) pasteurised, (C) homogenised–pasteurised, and ultra-high-pressure homogenised milk samples at (D) 100 MPa (Zamora. 2012)
That the process of homogenization will also affect the normal distribution of tri- and diacylglycerols, which are necessarily released from the core of the ruptured fat molecules (figure 3, top - blue) and modify the intricate phospholipid structure of the membrane (figure 3, top - red) should be as obvious as the fact that those tri- and diacylglycerols, phospholipids, cerebrosides and gangliosides are suddenly part of the skim fraction are easily lost during further processing (such as the removal of fat) and will have different physical attributes, physiological effects, digestive properties and absorption kinetics (cf. Berton. 2012).

The degree of homogenization increases according to the pressure that's used to force the the hot milk between valve needle and seat of the homogenization machine, so that  the aforementioned effects are particularly pronounced in the high-pressure homogenized milk (also "ultra-homogenized" milk). Accordingly even the last few "unwanted" (by the food industry) larger, intact fat globules that are left in the regular homogenized milk (figure 3, C) break apart.

What used to be a huge container-like fat molecule in the raw milk (figure 3, A), survived the pasteurization process relatively unharmed (figure 3, B) is now, after it has been pressed with 100MPa through the valve of the homogenization machine, nothing but a heap of very shelf-stable and non-clumping, highly convenient debris (figure 3, D) - awesome, right?
Bottom line: Aside from the disgusting taste of what we here in Germany call "H-Milch" ("h" as in "haltbar", which denotes the longer shelf-life) the structural changes and the potentially problematic downstream effects of the homogenization process, such as
Image 2: Assuming that the plastic canister the girl on the right holds in her hands contains homogenized milk, it may in fact be better for the girl on the left, if it was fat free :-o After all, when the homogenized whole milk is further processed into 0.2% = no fat milk ~95% of the previously created mutant fat molecules will be removed ;-)
  • a rise in potentially artherosclerotic free bovine xanthine oxidase, which would otherwise be "locked" in the the intact milk fat globule membrane (MFGM),
  • the formation of new lipid layers from casein and other milk components and milk fat globule membrane fragments with potentially allergenic, and inflammatory properties,
  • a decrease in curd formation / stability, an increase proteolysis and lipolysis (=digestion of the proteins and fats) and the subsequent increase in nutrient absorption and speed in the gastrointestinal tract with its potentially detrimental downstream effects on blood lipids, and
  • the increased absorption of casein molecules and the loss of the beneficial health affects such as the anti-viral, antimicrobial, anabolic and gut protective effects that have been ascribed to the natural MFGM structure of milk
should be reason enough not to make the most convenient, but the most natural choice - and that irrespective of whether the milk is for a toddler, a child, a teen or an adult... and by the way, the changes the fat molecules in the milk are undergoing and the subsequent "mutant" protein + fat fragment structures they are forming make the otherwise nonsensical advice to use "low" or better "no-fat dairy" actually appear quite sensible.
Apropos "high fat dairy", did I mention that the "bad high fat cheese" is not just almost always made from regular, non-homogenized milk (which is hard to get, these days, as even the cooled milk is routinely homogenized, so make sure to check the label), but that its consumption is also associated with a decreased risk of developing metabolic syndrome (Høstmark. 2011)? No... well, than that's even more food for thought ;-)
References
  • Berton A,Rouvellaca S, Robertd B, Rousseaud F, Lopez C. Effect of the size and interface composition of milkfatglobules on their in vitro digestion by the human pancreatic lipase: Native versus homogenized milk fat globules. Food Hydrocolloids. 2012; 29:1, 123–134. 
  • Ho C, Clifford A Bovine milk xanthine oxidase, blood lipids and coronary plaques in rabbits.J Nutr. 1977; 107, 758–766
  • Høstmark AT, Tomten SE. The Oslo health study: cheese intake was negatively associated with the metabolic syndrome. J Am Coll Nutr. 2011 Jun;30(3):182-90.
  • Kohno Y, Honma K, Saito K, Shimojo N, Tsunoo H, Kaminogawa S, Niimi H. Preferential recognition of primary protein structures of alpha-casein by IgG and IgE antibodies of patients with milk allergy. Ann Allergy. 1994 Nov;73(5):419-22.
  • Laugesen M, Elliott R. Ischaemic heart disease, Type 1 diabetes, and cow milk A1 beta-casein. N Z Med J. 2003 Jan 24;116(1168):U295.
  • Michalski MC. On the supposed influence of milk homogenization on the risk of CVD, diabetes and allergy. Br J Nutr. 2007 Apr;97(4):598-610.
  • Oosting A, Kegler D, Wopereis HJ, Teller IC, van de Heijning BJ, Verkade HJ, van der Beek EM. Size and Phospholipid Coating of Lipid Droplets in the Diet of Young Mice Modify Body Fat Accumulation in Adulthood. Pediatr Res. 2012 Jul 31.
  • Tailford KA, Berry CL, Thomas AC, Campbell JH. A casein variant in cow's milk is atherogenic. Atherosclerosis. 2003 Sep;170(1):13-9.
  • Zahar M, Smith D- Adsorption of proteins at the lipid-serum interface in milk systems with various lipids. Int Dairy J. 1996: 6, 697–708.
  • Zamora A, Ferragut V, Guamis B, Trujillo AJ. Corresponding author contact informationChanges in the surface protein of the fat globules during ultra-high pressure homogenisation and conventional treatments of milk. Food Hydrocolloids. 2012; 21:1, 135–143.