cont…
Indeed there are several lines of evidence raising concerns with milk and dairy intake, such as:
1) Milk and fermented milk (yoghurt, for instance), despite having a low glycemic index and load, elicit a very high insulin response and this has been shown repeatedly in intervention studies. As you may be aware, constantly increasing insulinemia may downregulate the insulin receptor, and hence lead to insulin resistance, which in turn is the primary metabolic defect underlying The Metabolic Syndrome, and may be a driving force in obesity. It should also be mentioned that a chronic state of Hyperinsulinemia may set a hormonal cascade. That ultimately results in cancer, acne and juvenile myopia, among other diseases. Indeed, a high bovine milk diet has been shown to cause insulin resistance in boys. Moreover, dairy intake is strongly associated with a higher incidence of Acne and moderately associated with Prostate Cancer.
2) Cow’s milk appears to be involved in certain autoimmune diseases (AD): Various epidemiological studies have associated it with Type 1 Diabetes IgA nephropathy, Behçet’s disease.
3) Hormones in Milk: In addition to proteins, fats, lactose, vitamins and minerals, milk contains various growth-stimulating steroid and peptide hormone and also catalysts, transporters and stabilizers that ensure their maximum bioactivity. Here’s a short list of some hormones present in cow’s milk that could be problematic for humans:
Insulin
Cow’s Milk, as well as human milk (and presumably milk from all mammals) contains insulin, and 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 who have been exposed to infant formulas containing cow’s milk. This not only confirms that BI is present in commercial pasteurized milk, but also in infant formulas and perhaps other dairy products (although direct evidence is lacking). Moreover, these studies 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, various 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 relevant, since pasteurization (time and temperature are crucial factors) and fermentation appears to reduce its content. Yet cow’s milk consumption, compared to various foods, is associated with a higher plasma IGF-1 concentrations in humans (both children and adults),
which could be due to calcium in milk (which 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 milk could lead to a higher plasma IGF-1 or indeed residual IGF-1 in casein (protein in milk).
Betacellulin
Betacellulin (BTC) belongs to the Epidermal Growth Factor family of hormones, and is found not only in cow’s milk and whey, but also in cheese. Therefore, it survives pasteurization and processing. Although no direct evidence yet exists, bovine milk does contain peptidase inhibitors which prevent human gut enzymes from degrading EGF (and most likely BTC), and a low ph such as that found in the gut, it does not impair or prevent BTC from binding its receptor. 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 metabolites levels are greatly elevated. Confirming this, US researchers have measured estrogen metabolites in various milks and shown that buttermilk contains the highest total amount of estrogen metabolites, followed by skim milk, 2% milk and whole milk. Therefore, estrogen metabolites appear to survive pasteurization, and estrone sulphate, which comprises 45% of the conjugated estrogens in Premarin and Prempro (the most frequently prescribed hormone replacement therapy for menopausal women) has high oral bioactivity, and is the most prevalent form of estrogen in cow’s milk. There are also other steroid hormones in commercial pasteurized cow’s milk, such as progesterone, 5α-androstanedione and 5α-pregnanedione, which are dihydrotestosterone (DHT) precursorer. As expected from the evidence presented, dairy intake is strongly associated with a higher incidence of acne, moderately associated with prostate cancer, and mildly associated with ovarian cancer. Dairy consumption was also associated with an increased incidence of testicular, kidney, and head and neck cancer, but very few studies have been conducted to draw more significant conclusions. Although epidemiological evidence can’t show a clear cause and effect, and clearly much more studies need to be conducted, the current evidence strongly suggests that cow’s milk may be implicated in a variety of autoimmune diseases.-Pedro Bastos
