Milk is touted the world over as a healthy beverage for children and adults. Some claim that dairy calcium promotes weight loss, while others believe milk fat and whey protein may cause weight gain.
Most commercially produced milk today is homogenized, and its fat is often skimmed, thus the term “skim milk.” Processors homogenize milk to prevent the cream from separating out, and to increase its shelf life. They do this by pumping milk at high pressure through very narrow tubes, which breaks up the fat globules into smaller particles that cannot be completely covered by the original fat-globule membrane. The newly exposed fat surfaces attract casein micelles (submicroscopic aggregations of molecules), which create a new membrane structure around the smaller fat globules.
In addition to weighing down the globules, the casein interferes with the clustering of fat globules that result in cream separation. So homogenized milk tastes creamier in the mouth than non-homogenized milk, has improved digestibility, and generally has a longer shelf life than its non-homogenized counterpart.
Homogenization may not, however, be the best thing for milk destined for human consumption. Here’s why:
Nature created milk as an intrinsically intricate system of nutrients. Homogenization profoundly alters that system, making milk a very powerful and efficient delivery system of nutrients and compounds that humans didn’t consume until recently.
When you drink non-homogenized milk, your system absorbs native milk-fat globule membrane (MFGM) proteins. These are normally digested in the stomach or gut. However, homogenization decreases the size of milk-fat globules, making caseins the main protein fraction that the body absorbs. Homogenization allows for a greater amount of casein micelles to bypass normal digestion processes and be absorbed directly into the bloodstream.
So what, you ask? Well, homogenization transforms fat into small ‘capsules’ that can carry right into your bloodstream both the cow’s natural hormones and the ones they were injected with to enhance milk production. And that’s not all. Milk contains bioactive proteins, polypeptides, peptides, lipids (cholesterol and phospholipids), oligosaccharides, hormones and growth factors, additives such as vitamin D, bacteria, and possible traces of endotoxins, antibiotics, detergents/disinfectants and pesticides/insecticides.
As yet, we don’t know how common dairy processes such as homogenization activate, inactivate, or alter these components and what their putative impact might be on the health properties of milk. There are some clues, though.
Xanthine oxidase (XO) is an enzyme of large molecular size. Normally it is attached to milk’s fat globules, which, because of their large size are not easily absorbed by the gut wall. Fat miniaturized by homogenization, however, can enter the bloodstream directly and usher along the attached XO. Researchers have proposed that XO causes hardening of the arteries, which causes angina, heart attacks, congestive heart failure and strokes.
While research supporting the causal relationship between XO and hardening of the arteries is not clear-cut, one matter stands true: homogenization facilitates the entry of milk fat directly into the bloodstream that would otherwise be subjected to the digestive process in the GI tract.
– Michalski, Marie-Caroline, and Januel, Caroline. Does Homogenization Affect the Human Health Properties of Cow’s Milk? Trends in Food Science and Technology: Volume 17, Issue 8, August 2006, Pages 423-437.
– Michalski, Marie-Caroline. On the supposed influence of milk homogenization on the risk of CVD,
diabetes and allergy. British Journal of Nutrition, Volume 97, March 2007, Pages 598–610.
– Berkey CS, Rockett HR, Willett WC, Colditz GA. Milk, dairy fat, dietary calcium, and weight gain: a longitudinal study of adolescents. Archives of Pediatrics and Adolescent Medicine: Volume 159, Issue 6, June 2005, Pages 543-550.