The study was performed on milk from twenty-five separate farms, and found that milk from organic sources had sixty percent higher levels of a healthier fatty acid known to shrink tumors. Vaccenic acid, a substance linked to reduced risks of obesity, diabetes and heart disease, also appeared in the analysis. Organic milk contained about thirty percent fewer Omega-6 fatty acids than conventional milk, and almost forty percent more Omega-3 fatty acids, also connected with a lower heart disease risk. These beneficial substances appeared primarily in milk produced over the summer, when the cattle had access to fresh grazing foods.

In the UK, where this study was performed, more than eighty percent of organically raised cows’ diet comes from grass, versus conventional farms, which provide less than forty percent in grazing. In the US, forty percent of conventional dairies say that no cows are pasture fed at all, and grazing rates are also lower for organic dairies, due to differences in regulations. Sixty percent of organic milk producers say that their cows are on pasture at least half the time during the grazing months.

Hormone exposure is another factor. Human exposure to estrogens in cow’s milk, which accounts for sixty to eighty percent of the extrogens consumed by people who use dairy products, could have some serious side effects. Modern cows spend much of their time pregnant, which causes their milk to contain much higher amounts of estrogen and progesterone than the milk of cows raised in non-conventional settings, such as traditional herding societies. Two pilot studies at Harvard have been conducted to analyze these differences.

One study compared the levels of hormones and other growth chemicals in several types of US produced milk, including conventional products, organic milk, and ultra-pasteurized milk, with milk produced in a traditional fashion in Mongolia. US skim milk and Mongolian milk both contained much lower hormone levels than the other types. Hormones are mostly transmitted through fat, which is removed in skim milk. Whole Mongolian milk had lower levels than whole milk produced in the US.

The other study compared the connection between cancer rates and diet in forty-two different countries. High consumption of milk and cheese is closely correlated to high incidences of testicular cancer in younger men. In countries where milk consumption is low, rates were lowest. In countries where cheese and dairy are traditional foods, rates were high. And these statistics can chance fast – Japan’s rising dairy consumption rates are correlated with a much higher rate of cancer deaths. Breast cancer rates may also be affected by milk and cheese consumption.

Milk does contain some beneficial vitamins, though. Giving up milk entirely could cause a whole new set of health problems. The better choice is to stick to primarily low fat, organically produced milk. Ideally, we would get milk harvested only when the cows are not pregnant, but this is difficult, due to modern production practices. Slightly reducing milk intake and balancing our diets with other foods would alos be a great idea. Good quality milk can still be a great food, but you have to choose wisely.