Not to be outdone by Johns Hopkins, Harvard Medical Group also published a review in the New England Journal of Medicine about milk and health.
They start out by “stating the obvious” that the natural function of milk is to nourish and promote the growth of young mammals, not mature ones. They go on to question the current dietary recommendation of three 8-ounce servings of milk/milk product per day.
Because cows are bred for high milk production and because they are pregnant during most of the time they are milked, they produce high levels of insulin-like growth factor (IGF-1) and high levels of estrogen and other hormones.
Exposure to IGF-1 and other hormones has been linked to a greater risk for certain cancers: breast, ovarian, uterus and prostate.
Cow milk intake has been correlated with the development of diabetes, especially type 1 diabetes owing to cross reactivity between dairy proteins and pancreatic islet cells.
A long-standing rationale for promoting lifelong milk consumption is to meet calcium requirements for bone health. The concept is good but the practical outcome is the opposite. Hundreds of scientific studies show that countries with the greatest milk intake have the poorest bone density. Yes, milk is rich in calcium, but it also contains certain proteins that leach away the mineral content of our bones. Countries with the lowest milk intake paradoxically have the best bone health. Cow milk is also the most common cause for food allergy, at least in Western countries.
Finally, there is the “fart” issue. As hard as it seems to believe, the methane produced due to the large industrial scale of milk production is having a measurable effect on green house gases. The Harvard group calculated that obtaining our protein from alternative sources such as soy, legumes, and grains rather than from milk would reduce global greenhouse gases by 10 percent.