Homogenisation of milk is the process by which the fat on the milk is treated to allow mixing of the fat and water soluble components of the milk. This creates a product that retains the milk fat, but the fat does not settle on the top of the milk but is evenly distributed within it. Homogenisation occurs by forcing the milk through a filter of a very fine pore size that breaks up the milk fat to tiny globules. The hypothesis that homogenised milk might be a cause of cardiovascular disease was first postulated by Kurt Ostler in the 1960s. Ostler suggested that homogenised milk was a cause of cardiovascular disease because of the xanthine oxidase enzyme that it contains. Xanthine oxidase is an enzyme that can deplete cells of plasminogen. Plasminogen is a protein that is required to degrade fibrin in a process called fibrinolysis, and thus decrease clot formation. By depleting the cells of plasminogen, ostler hypothesised that atherslerotic plaque formation would be more likely to form leading to cardiovascular disease.
Milk is a good source of xanthine oxidase, and pasteurisation of milk destroys only around half of its activity. So whole pasteurised milk is high in xanthine oxidase. Ostler suggested that by homogenising the milk, the amount of xanthine oxidase adsorbed to the body would increase from that compared to non-homogenised milk and that this would in turn degrade plasminogen and increase clot and atherosclerotic plaque formation. He suggested that in non-homogenised milk the xanthine oxidase enzyme is located on the outside of the fat globules where it is digested in the intestine before absorption. However, in homogenised milk, the smaller fat globules were hypothesised by Ostler to allow the xanthine oxidase to be sequestered inside the globules and thus their digestion inhibited significantly. Evidence for Ostler’s theory came from a close approximation between the time homogenized milk was introduced to the Western diet and the rise in the cases of cardiovascular disease.
The evidence that homogenised milk may be a cause of cardiovascular diseases has been extensively studied. A review article published in the American Journal of Clinical Nutrition back in 1983 investigated the evidence to date for the homogenised milk hypothesis of cardiovascular disease1. The review concluded that the absorption of xanthine oxidase had not been conclusively demonstrated in the nutritional literature. Yes, the authors conceded that xanthine oxidase from homogenised milk could survive passage through the stomach, but there was no evidence that this xanthine oxidase was able to raise plasma levels anymore than from non-homogenised milk. Further, a conclusive association between homogenised milk and cardiovascular disease had not been established. Further the review suggested that the ability of xanthine oxidase to deplete plasminogen was not evidenced convincingly. In addition, there were doubts as to whether the intact fat globules in homogenised milk could be absorbed in humans.
Dr Robert Barrington’s Nutritional Recommendation: Eating whole foods in their natural state nearly always provides the best health outcomes. When whole foods are eaten, many of the potential and controversial pitfalls are avoided. Drinking non-homogenised pasteurised milk therefore avoids any potential problems with xanthine oxidase absorption. However, having said this the theory that homogenised milk is a cause of cardiovascular disease is controversial and there is no real strong evidence either way. My personal recommendation is to drink non-homogenised milk to remove any doubt from the issue.
RdB
