Dairy - Yay or Nay?

milk_bottles_headerRemember the days when we were all encouraged to drink 3 glasses of milk a day? What happened?! Nowadays the words "dairy-free" appear on menus all over North America, and the health-conscious set seem to avoid it like the plague.

So what gives? What could possibly motivate people to give up milk and cheese in favour some pretty strange substitutions? (non-dairy cheese, anyone?)


A Brief History of Dairy

Milk has been consumed in various forms for thousands of years, and became a daily household commodity in North America and Europe in the mid-1800s. This was thanks in large part to Louis Pasteur, who in 1863 invented pasteurization - a method of flash-boiling liquids to kill harmful microbes.

For quite some time milk was considered a relative super food - high in calcium and protein, it was perceived as a cost-effective way to fatten up your children and keep your family healthy.

Then, in the 1990s, the tables started to turn. More and more health-conscious folks began avoiding dairy, opting instead for things like soy milk.


What Does Dairy Do?

Research has shown that the link between cancer and dietary hormones is quite strong. While some estrogen is obviously necessary to a healthy body (it is the female sex hormone, after all), high amounts have been positively correlated to incidences of prostate cancer in men, and breast and ovarian cancer in women.

I've written before here about xenoestrogens - harmful environmental toxins that mimic estrogen in the human body. Well, natural estrogen is almost 100,000 more potent than those xenoestrogens.

And dairy milk is laden with it.

A study in Japan revealed that regular consumption of milk only began after the Second World War, and positively correlated to significantly elevated levels of prostate cancer (in 1954 a law mandated that all school children drink 200 ml of milk a day; at that point, milk had only been part of the Japanese diet for a couple of years).

Other studies have shown similar results: the high amount of estrogen in milk may be strongly linked to high cancer rates in countries where dairy is consumed.


The Culprit: Industrialization

"The milk we drink today is quite unlike the milk our ancestors were drinking," Harvard researcher Ganmaa Davaasambuu, an expert on milk-related illnesses, said during a 2006 talk at the Radcliffe Institute for Advanced Study.

According to Davaasambuu, milk's fall from grace is largely the fault of the industrialized food system.

In today's conventional dairy farming, cows are milked over 300 days of the year, and are hence almost constantly pregnant. In pregnancy the cows produce higher levels of hormones - including estrogen - and these hormones are passed on in their milk.


Hormones Found in Milk

Estrogen may be the main culprit, but other hormones are lurking in today's dairy milk:

  • Prolactin – released during the cow’s lactation period, with the highest concentration during the first days after parturition.
  • Insulin-like Growth Factor-1 (IGF-1) – often elevated due to use of growth hormone injections to increase milk yield, but also naturally exists at higher concentrations in milk colostrum. Milk IGF-1 is not destroyed by pasteurization and will be present in shelf milk. It plays an important role in cellular growth and metabolism, and can promote tumour development by stimulating cell proliferation. High levels of IGF-1 are associated with an increased risk of developing tumours of the prostate, breast, endometrium, pancreas, and colon.
  • Glucocorticoids – steroid hormones that may be present due to the widespread use of dexamethasone, a prescription drug (corticosteroid) used for the treatment of various inflammatory diseases in veterinary medicine. Stressful conditions, such as transport, diet changes, changes in environment, and other stressful factors may also contribute to the levels of these hormones in milk.
  • Androgens – steroid hormones, like testosterone, whose concentrations are increased during pregnancy.
  • Progesterone – mainly concentrated in the fat fraction of milk, progesterone helps regulate and maintain pregnancy, and plays a role in the development of mammary glands in breast tissue.

Dairy, Yay or Nay?

Like so many things in this world, your choice to consume dairy is highly personal, and should probably include a bit of flexibility.

For instance, I never drink dairy milk... unless I occasionally feel like a tiny bit of organic cream in my morning coffee. I also avoid cheese... unless I'm at a party and they have delicious local brie on offer. As in all things, moderation is key.

What's pretty clear, though, is that regular consumption of dairy, particularly dairy milk, may increase your likelihood of cancer. Seems like pretty good reason to say (conditionally) nay to dairy products.