Nutrients
Exosomes: The X-Factor in Milk
Exosomes are tiny fat droplets in milk that transport RNA and growth factors—and may be the long-sought X-factor that gives milk its special effects on muscle growth.
Nutrients
Exosomes are tiny fat droplets in milk that transport RNA and growth factors—and may be the long-sought X-factor that gives milk its special effects on muscle growth.
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"X-Factor: The Inexplicable.
We live in a world where dream and reality stand close together. Where facts often seem like figments of imagination we cannot explain. Yours, Jonathan Frakes."
Who doesn't know this intro from the classic American TV series? It's about the mysterious. About the x-factor, the unknown variable that mysteriously influences our lives.
Milk has always held something mysterious—something we couldn't (yet) explain.
For example, in 2004 researchers [source no longer available] conducted a study with 24 eight-year-old boys who consumed either 1.5 liters of low-fat milk or the equivalent amount of protein from meat daily for one week. Result: Only in the milk group did the growth hormone IGF rise in the serum.
Strange, isn't it? Sure, milk might contain a few more calories than lean steak. But that doesn't explain the sharp increase in growth hormone in the children's blood, because the protein content was identical.
Apparently surprised by the results, researchers conducted [source no longer available] of the data, whose findings were published the following year. Result: Insulin levels in the milk group doubled! And simultaneously, so did insulin resistance.
Mind you, here again: In the meat group... nothing happened.
Years before, the scientific literature had already noted a discrepancy between the glycemic index and the insulinemia index for milk. That is, the insulin spike is significantly more pronounced in relation to the carbohydrate quantity consumed in milk. In this context, researchers spoke of an "insulinotropic effect" and a "yet-unidentified component in milk." An X-factor.
Since then, whenever an epidemiological study finds a link between milk and any health event (e.g., cancer), that's exactly what's cited as the explanation: Milk simply stimulates too much insulin and growth hormone, which in turn fuels tumor growth.
Only about a decade ago did the scientific community take notice. A German researcher named Bodo Melnik from the University of Osnabrück suddenly introduced a completely different player into the picture: exosomes.
Exosomes are tiny fat droplets surrounded by a membrane that transport mRNA, miRNA, and growth factors in a way that's resistant to digestion and highly bioavailable. They're abundant in milk and are thought to regulate genes in offspring—this is how nature accomplishes information transfer and maternal protection through breast milk. Incidentally, this applies to humans too.
In his [source no longer available], Melnik called milk "a genetic transfection system that activates mTORC1 signal transduction for postnatal growth." Transfection has become familiar to us since mRNA vaccines: the term describes introducing RNA or DNA into target cells or organisms, where they work.
Milk exosomes do exactly that: milk sends RNA via exosomes into the body of the milk drinker—ideally a calf or a human child. And there, according to Melnik, it activates mTOR—the ultimate growth switch in our cells. Purpose: prevent catabolism (breakdown), drive anabolism (buildup). Logical.
The transported substances use sophisticated mechanisms in various tissues to ensure that, by day's end, the body becomes more anabolic or more anti-catabolic. And this goes hand-in-hand with increased insulin secretion or reduced insulin degradation, so more insulin remains in the blood and the body stays more anabolic.
In this sense, milk might be the oldest and most modern "genetic technology" that exists. PubMed statistics show that both research into exosomes generally and research into milk exosomes specifically have grown exponentially over the past decade—an extremely rapid development of the field.
There's something to the X-factor.
Researchers discovered the X-factor in milk [source no longer available] when trying to determine why whey protein—the whey component of milk—has such a proven favorable effect on muscle growth. They showed that neither the high leucine content of whey nor the high proportion of essential amino acids needed for muscle building could explain why whey works so well.
And then it occurred to them... exactly... the work by Melnik and colleagues on milk exosomes. As a result, they simply isolated the exosomes from the whey and "dripped" them onto muscles in a test tube. Result: "Exosomes derived from whey protein increase protein synthesis and hypertrophy in mouse muscle cells."
Milk exosomes along with their contents appear to have a growth-stimulating effect on muscle cells. So exosomes are the magic in milk. However, discussions will now follow about whether this "genetic transfection system" that milk and milk products apparently are is really so beneficial for every adult or in every health context.
In 2021, a study was published in which researchers examined the effect of milk exosomes on a tumor. With fascinating findings. We discuss that [source no longer available].
