Horomones in our dairy

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HOROMONES IN MILK
The existence of hormones in cow's milk that could be problematic for humans. Before we discuss the potential adverse effects of each of those hormones, it is important to know that in order for any of these milk hormones to potentially cause or promote a certain disease, it must:
1. Survive the pasteurization and processing methods
2. Survive the human digestive processes intact
3. Cross the gut barrier intact

It is normally believed that protein shearing enzymes in the human gut breakdown proteins and hormones before they can get to the small bowel where absorption occurs. This is what happens when you eat protein-containing foods, such as beef or fish, and this is the reason why some diabetics have to take insulin intravenously and not orally.

Nevertheless, we should remember that milk's main purpose is to accelerate growth in weaning mammals, who have a low endogenous production of hormones. Milk contains not only the necessary hormones to promote growth, but also catalysts, transporters and stabilizers that ensure their maximum bioactivity. Cow's milk also contains peptidase inhibitors that could prevent proteolytic breakdown of various peptide hormones and growth factors, such as IGF-16 and the EGF family of hormones (like betacellulin).

The evidence suggests that most of the hormones mentioned last week fulfill, at least, the first two of the above requirements: surviving the pasteurization and processing methods, and surviving the human digestive processes intact.

Insulin:
Cow's milk, as well as human milk (and presumably milk from all mammals) contains insulin.
We know that bovine insulin (BI) (which differs from human insulin by three amino acids) survives pasteurization because immunity to this hormone is common in children who consume cow's milk or infant formulas containing cow's milk. This not only confirms that BI is present in commercially pasteurized milk, but also in infant formulas, and perhaps other dairy products (although direct evidence is lacking). These studies also provide evidence that BI survives the human digestive processes and crosses the gut barrier intact, although this could be related to the fact that infants have higher intestinal permeability than older children and adults. Nevertheless, var ious factors may cause the so called "leaky gut" in virtually everyone, so we shouldn't dismiss bovine insulin altogether.

IGF-1:
Cow's milk contains active IGF-1, but this has been largely dismissed as irrelevant since pasteurization and fermentation appear to reduce its content. Yet, cow's milk consumption is associated with higher plasma IGF-1 concentrations in humans (both children and adults). This could be due to the calcium in milk (that has been shown to increase IGF-1 in boys and girls), the effect of milk upon insulinemia (the high elevation of plasma insulin caused by drinking milk could lead to higher plasma IGF-1 ) or residual IG F-1 in milk

Betacellulin:
Betacellulin (BTC) belongs to the epidermal growth factor family of hormones, and it is found not only in cow's milk and whey, but also in cheese. It survives both pasteurization and processing. Although no direct evidence exists yet, bovine milk contains peptidase inhibitors that prevent human gut enzymes from degrading EGF5 and most likely BTC. Additionally, a low ph, such as may be found in the gut, does not impair or prevent BTC from binding its receptor.5 Finally, there is a luminally expressed EGF receptor in the gut through which BTC may enter circulation.

Steroid Hormones:
The major sources of animal-derived estrogens in the human diet are believed to be milk and dairy products, which presumably account for 70-80% of the total estrogens consumed. Furthermore, it has been pointed out that most milk for human consumption is obtained from cows in the latter half of pregnancy when estrogen metabolite levels are greatly elevated. To confirm this, US researchers Daniel Falow and colleagues have measured estrogen metabolites in various milks and have shown that buttermilk contains the highest total amount of estrogen metabolites, followed by skim milk, 2% milk, and whole milk. So, estrogen metabolites appear to survive pasteurization, but do they survive the other necessary steps? It is highly possible because estrone sulphate, which comprises 45% of the conjugated estrogen in Premarin and Prempro (the most frequently prescribed hormone replacement therapy for menopausal women), has high oral bioactivity, and it is the most prevalent form of estrogen in cow's milk.

There are also other steroid hormones in commercially pasteurized cow's milk, such as progesterone, 5α-androstanedione, and 5α-pregnanedione, which are dihydrotestosterone (DHT) precursors. Unfortunately, we aren't aware of any study that has looked at the absorption of these hormones, so we don't know if they can survive steps 2 and 3: surviving the human digestive processes intact and crossing the gut barrier intact.