How to Kill a Craving, Part II

To preface today’s post, I want to reiterate what I mentioned at the close of my previous to last post. When I turn to the internet to educate myself on a topic, I do what I can to vet out claims that are backed by a particular industry lobby (of particular relevance to this topic is the soy lobby, who are not the granola-eating, Birkenstock-wearing ensemble of yogis one might suppose them to be) or worse, plain bad science. I usually look for a) what research was conducted to back the claim being made and b) who sponsored that research. If a particular claim references research that was published in a peer-reviewed journal, all the better, however this is rarely the case and it’s otherwise frustrating when evidence is given that may have good merit, but the writer has failed to cite his or her sources. So what follows are my conclusions from a review conducted under these criteria, and my references point to the original source of the data wherever possible. As a reminder, this whole review was sparked by a particularly sudden and unexpected cheese craving in a train station (see previous post)

Having led with that footnote, let’s go back to the beginning. When, exactly, did we decide it was a good idea to drink the milk of another mammal? None of the other animals are doing it. It's actually a relatively recent occurrence in the history of man: somewhere around 10,000 and 6,000 years ago there was a switch from hunting goats and cattle for their meat to domesticating them for their meat and milk (1). It’s important to note that only the Western world started and continues this practice. The majority of the world’s population has a dairy-free diet, and this becomes important later on when we look at why non-milk consuming countries have the best bone strength (which I’m interested in as an athlete).

The agricultural revolution brought dairy farming along in leaps and bounds. By the 1940's, we’d developed various ways to make a cow produce an average of 3,000 litres of milk per year, which is about 5 times the amount that a calf would normally drink (2). These days, we achieve over 6,300 litres per cow per year (3). These impressive gains in milk yields have been achieved through a number of methods, which are only relevant to my topic here in as much as they are relevant to what ends up in our milk as a result.

So bear with me as I run through the life cycle of a modern dairy cow; it really is worth it in terms of getting to the bottom of things. And the punch line at the end is highly rewarding, I promise.

Within hours after giving birth, the dairy cow's calf is taken from her. Male calves are sold for pet food or become veal (since dairy cows are bred for intensive milk production, the little-boy calves are a sort of unwanted by-product). The female calves are sequestered until they are old enough to be artificially inseminated to begin milk production (a cow must obviously first become pregnant and have a calf in order to produce milk). From that point on, she will be milked for 10 months out of the year, including seven months of each of her consecutive nine-month pregnancies (4). This practice of milking pregnant cows will become important later on – stay with me.

Once she begins her milk production, the dairy cow is treated with a number of hormones to further increase her yield. She is also fed a high-protein diet that contains nothing that she would naturally eat (grass is so passé for dairy cows). When it recently became apparent that turning natural herbivores into carnivores and, later, cannibals, was not very well thought-out (think BSE), most countries have switched to feeding genetically-modified soy and fish meal to dairy cows to keep the high-protein diet up.

Back to the hormones though. We’ve all heard that there are artificial hormones in our milk, so I’m not going to get into the details of which ones and in what amounts. Suffice it to say, there’s a lot. The most controversial, Bovine Somatotrophin (BST), has endless studies linking it to girls starting puberty at younger and younger ages (the average age is now 11 in North America – and there are plenty of cases of girls developing breasts at 9 and 10 years old (5). This makes some intuitive sense to me, since these are hormones designed to stimulate the mammary glands. (Sidenote to those of us in Europe and Canada: while BST milk has been banned in our countries, the ban does not apply to imports of dairy products, e.g. ice cream, from BST-legal countries such as the US).

All of this high-intensity milk production is bound to cause some stresses on the cow’s health, so a medley of antibiotics, the most common being penicillin, are used to treat the various illnesses related to this, pardon the pun, labour-intensive life. One of the most common afflictions for a dairy cow relates to the actual milking process. Being milked two to three times a day, seven days a week, by an electric milking machine tends to result in mastitis, an inflammation of the udders that causes them to become hot and hard and produce an abnormal discharge. Some 35-40 incidences of mastitis are found per 100 cows (6). Antibiotics are injected directly into the udder to reduce the swelling of mastitis, but that doesn’t stop the abnormal discharge. So certain amounts of these antibiotics are not the only thing to end up in our milk – avert your eyes from the rest of this sentence if you have a sensitive stomach – the presence of puss in our milk is completely normal and legal (7). This point becomes important later on, when we look at why it’s become necessary to heat our milk to very high temperatures (pasteurization) to kill, amongst other things, the bacteria in the puss.

(Another side note: this for those who chose organic milk in an effort to avoid the artificial hormones and antibiotics, as I used to. The organic dairy cow is still subject to the cycle of artificial insemination and continual intensive milk production, and because they are not given medication to treat the various associated stresses...yes, you guessed it, sick cows are being milked. The extent of this varies widely from organic dairy farm to organic dairy farm, but you can bet there is some serious puss in organic milk, not to mention the absence of pain relief for the cow suffering from mastitis, lameness and various systemic infections (8)).

Back to the life cycle: a dairy cow lives for an average of four years; under natural conditions, she might live up to 25 years (9) (so that hyperbole about dairy cows literally being ‘milked to death’? It’s perhaps not as far from the mark as I’d assumed). At the end of four years, her milk production begins to decline and she is transported to her final destination - the slaughterhouse. Interestingly, about 40% of America's hamburger is made from "spent" dairy cows.

Besides the presence of hormones and antibiotics in our milk, there is a little bit of an issue that arises from us drinking the milk of cows that are perpetually pregnant. I think this is where my doctor’s acne link might come into play. Various natural hormones are produced during pregnancy (mostly dihydrotestosterone, DHT, precursors) that stimulate the growth of skin cells and signal the skin cells to produce more sebum. These, in addition to the cow’s other growth-stimulating hormones that are there because a baby cow requires them for growth and development, and you might just have an acne-causing cocktail (10). Incidentally, these same growth-stimulating hormones, which are entirely natural and appropriate for turning a baby calf into a 1000-pound steer, are a little less appropriate for adult humans and are known to cause excessive cell growth by another name: cancer (11). (There is so much research on this that I don’t even know what to reference – just google dairy and any kind of human cancer, in particular breast cancer, for rather obvious reasons)

So now we are done with the cow, and we are close to the punchline, I promise. If you’ve stayed with me this far, then you deserve to know what good nutrients are in a glass of cold milk. The ones I had always had in mind, especially as an athlete, were protein and calcium. But before we look at that, we have to talk about pasteurization - try and stay with me.

Pasteurization, the heating of milk to very high temperatures, kills harmful microorganisms that may be living in the milk (remember the puss). Cooking the milk at high temperatures, unfortunately, also destroys all of the enzymes (this is actually the test for successful pasteurization) including lactase, contributing to lactose-intolerance. It also either destroys or alters the chemical structure of the naturally-occurring vitamins so that many are no longer bioavailable. So all that calcium that is packed in a glass of cold milk? We can’t ingest much of it (12).

This again makes some intuitive sense: North America has one of the highest consumptions of dairy products, and also the highest rate of osteoporosis. There is actually evidence (way too complicated to go into here) that consuming diary products causes the loss of calcium from our bodies. Worldwide, the lowest rates of osteoporosis are found in the populations that consume little or no dairy at all. For example, the women of the Bantus tribe in South Africa exist on a laregly plant-based diet and consume about 200 to 350 mg of calcium a day, about half of western women's intake. The women have virtually no osteoporosis despite bearing six or more children and nursing them for prolonged periods (13). When African women immigrate to the United States, do they develop osteoporosis? The answer is yes. Similarly, osteoporosis incidence in female Asians is much lower than in Asian females living in the USA (14), so it's not something in the genes of Westerners that makes us more susceptible to brittle bones, it's something else that we're doing.

But here's where it gets even more interesting for athletes: it seems that pasteurization might just kill something else that we think we are getting in milk. Things get muddy here, because there are many different pasteurization techniques and temperatures used, and the laws vary from country to country. Milk protein consists of two major proteins: casein and whey. As far as I can tell, there is decent evidence that both whey and casein start to denture when exposed to temperatures over 72C (15, 16). Most pasteurization techniques now cook milk at temperatures over 75C, not least of all over growing fears about the paratuberculosis virus, which is linked to Crohn's Disease (17). The dairy industry firmly states otherwise, but non-dairy-sponsored research suggests that the proteins in modern pasteurized milk are in varying denatured states.

If you're tired of reading this ridiculously long post, you might have just missed the punchline, so I'll spell it out. If the vitamins and minerals in milk are no longer in bioavailable form, and the proteins have been denatured, then what we are left with is a rather bizarre cocktail of artificial and natural cow hormones, antibiotics, saturated fat and some carbohydrate.

I think that did it, my cheese craving seems to have passed.

1. http://answers.google.com/answers/threadview/id/741074.html
2. Epstein, S. S. Potential public health hazards of biosynthetic milk hormones. International Journal of Health Services, 20:73-84, 1990.
3. FAWC, 1997. Report on the Welfare of Dairy Cattle. Farm Animal Welfare Council. Surbiton: Surrey
4. MAFF, 2001. Welfare of Calves. Ministry of Agriculture, Fisheries & Food.
5. Stoll BA. Western diet, early puberty and breast cancer risk. Breast Cancer Res Treat (England) Jun 1998;49(3):187-93.
6. FAWC, 1997. Report on the Welfare of Dairy Cattle. Farm Animal Welfare Council. Surbiton: Surrey
7. http://www.ag.ndsu.edu/pubs/ansci/dairy/as1131w.htm
8. www.organicconsumers.org
9. Winter, M., Fry, C. and Carruthers, P., 1997. Farm animal Welfare and the Common Agricultural Policy in Europe. Compassion in World Farming Trust. Petersfield: Hampshire
10. Holmes et al. Dietary Correlates of Plasma Insulin-like Growth Factor I and Insulin-like Growth Factor Binding Protein 3 Concentrations, Cancer Epidemiology Biomarkers & Prevention Vol. 11, 852-861, September 2002
11. Outwater JL, et al. Dairy products and breast cancer: the IGF-I, estrogen and bGH hypothesis. Med Hypotheses Jun 1997;48(6):453-61
12. Lanou, A. Pediatrics, March 2005; vol 115: pp 736-743.
13. Walker, A., Osteoporosis and Calcium Deficiency, Am. J. Clin. Nutr. 1965 / 16 / 327.
14. Memon, A. et al, Incidence of hip fracture in Kuwait. Int.J.Epidemiol.1998 / 5 / 860-865.
15. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T7C-4CHRJ1H-4&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=5b9ccebebefce3d241edf7a1df846e7e
16. http://www3.interscience.wiley.com/journal/119136566/abstract?CRETRY=1&SRETRY=0
17. Collins MT. "M paratuberculosis in Foods and the Public Health Implications." Proceedings of the Fufth International Colloquium on Paratuberculosis, Chiodini RK, Hines ME, and MT Collins (Eds.) Madison, WI: International Association for Paratuberculosis, 1996:352