Is homogenized milk really dangerous?

At Ljubljanske mlekarne the safety of the consumer is our main concern and we really want everyone to enjoy quality and delicious dairy products. Articles about the alleged danger of homogenized milk appear occasionally in different media or web pages.

We can assure you that homogenized milk is in no way hazardous. For this reason, we are publishing in its entirety an article by Prof. Dr. Irena Rogelj from the Chair of Dairy Science at the Biotechnical Faculty in Ljubljana, which she wrote in response to assumptions regarding the dangers of consuming homogenized milk.

I felt compelled to write this piece by an article entitled »Homogenized milk is a slow killer«. Actually, more than the article itself, I was encouraged to write this by the letters of readers who call to action the entire Slovenian public, including the president of the state, horrified by the dangers of this killer. It is true that we Slovenians (and not only Slovenians) like sensations; however, food is not a suitable field for such games.

People are well aware of the connection between food and health. Intimidating passages about the harmfulness of milk fat in homogenized milk under headlines that emanate »mortal danger« surely scare them and discourage them from drinking this type of milk. And this is how it should be, you would say! It’s true; this is how it should be, if these articles were based on scientifically proven facts, confirmed by research and scientific communities. Oversimplification of scientific discoveries about the link between food and health can lead to completely wrong conclusions. Therefore, we have to be careful about how »sensationally« we write about food, and should not confuse people with »half-truths«. Think about what was already written on the harmfulness and benefits of butter and margarine alone, and about sugar and artificial sweeteners, tomato and carrot juice.

If we asked real nutritionists, they would assure you, based on everything that was thus far scientifically established, that it is absolutely impossible that milk fat, consumed through milk, would directly pass through the digestive tract into the circulatory system.

But let’s proceed in order! The main body of milk fat (around 98 percent) is represented by triglycerides (triacylglycerols), which consist of one glycerol molecule and three fatty acid molecules (they may be identical or different). Fat is located in milk, in balls of fat (droplets), which are distributed in the water phase in the form of emulsion. It is produced in cells of the mammary gland. When fat exits the mammary gland cell, it covers itself with a membrane that contains many phospholipids and proteins. According to size, the balls of fat fall into three groups: small, with a diameter up to 1 micron, mid-size, with a diameter between 3 and 5 microns, and large, with a diameter between 8 and 10 microns. 70 to 90 percent of balls of fat in cow’s and also human’s milk belong to the first group. They are smaller than 1 micron and their size is the same as the balls that formed during homogenization. In fact, during homogenization larger balls break-up the smaller ones with a special procedure. Thus, the total surface of the balls (i.e. the surface through which enzymes, which break down fat cells, can affect fat during digestion) increases. The surface of the newly formed balls is covered by casein micelles and submicelles, and in a smaller extent by serum proteins. These substances would, as argued by the article published in your magazine, actually protect the balls of fat from the effect of the so called lipolytic enzymes, i.e. enzymes that break down fat, if it wasn’t for acid-sensitive caseins (low pH values) losing their electric charge (and also stability) in the stomach area. This is why they are easily accessible to digestive enzymes and thus easy to break down (and not the other way round!). Once caseins, which »protect« the droplets of fat, are broken down, the droplet of fat is not protected anymore from enzymes that break down fat. Based on these findings, scientific articles cite that homogenized fat is more easily digestible than non-homogenized.

After this simplified explanation, I will try to explain in the following text why balls of fat, even though very small, cannot »jump« through the intestinal wall and then stick to the walls of the circulatory system.

When we want to talk about how food influences health, we have to have at least basic knowledge of nutritional physiology, in our case the knowledge on digestion and absorption of fats. The process of digesting fat starts in the stomach, where with the aid of gastric acids and the movement of stomach muscles fat is distributed in the stomach’s content in the form of emulsion. Milk fat, as opposed to other types of fat, does not enter the stomach in this form. Fat begins to be truly broken down in the small intestine (jejunum), where the lipase enzyme separates fat from fatty acids and glycerol and a small quantity of monoglycerides, whereas the phospholipase enzyme breaks down the phospholipids of the membranes. Proteins (also caseins) are starting to be broken down by the gastric acid and pepsin already in the stomach, and their digestion by proteolytic enzymes continues in the small intestine. The fat in the water mixture of the small intestine is not soluble. Smaller balls could quickly join creating bigger balls. For a successful functioning of lipase enzymes, special emulsifiers – bile acids have to keep these balls as small as possible, in the form of fine emulsion! Once fats are broken down to their components, these components (glycerol and fatty acids) penetrate (diffundate) in the form of small complexes, named micelles, the intestinal cells (enterocytes). There, the synthesis of fats starts again. In terms of their composition, these fats are different from fats present in digested food. Triglycerides that link together with phospholipids and apolipoproteins form hylomicrons, which also contain other products that were formed during the digestion of fat, such as cholesterol and liposoluble vitamins. Hylomicrons then enter the lymphatic system, and thus their journey through the body begins. However, hylomicrons are just one form of lipoproteins carrying fat around the body. But this is another complex story, with which we would be able, taking into consideration the quantity and components of the consumed fat, to explain in a much more detailed way the connection between food (fat) and the diseases of the heart and cardiovascular system as opposed to a simplified story, in which homogenized milk is the guilty party this time.

Is it possible to recycle homogenized milk?

There are many industries and technologies in the world today that make possible the production of final products even from raw material of lower quality. Milk processing does not allow this – quality dairy products can be produced only from quality milk. At Ljubljanske mlekarne we give special attention to this. We organized our care for product safety and quality into a comprehensive system that begins with raw milk quality control at the producer and ends when each individual product reaches the end consumer.

Returning expired products to production facilities is prohibited by law and we fully comply with this. This is also strictly verified by veterinary inspectors. At Ljubljanske mlekarne we carefully check all incoming raw materials or raw milk, which must be truly fresh, and the time between the milking and the acceptance in the dairy must be the shortest possible. We also verify that milk complies with all quality regulations prescribed by the applicable law of the European Union.

What do the numbers on the bottom of the milk’s Tetra Pak packaging mean?

The packaging supplier of our milk is the company Tetra Pak, which explained to us what the numbers printed on the bottom mean. The packaging is printed on several belts simultaneously, which have to be numbered for tracking reasons. The number 12 45, for example, means that the packaging was printed at the third belt in the production process.