With the acceptance of dairy products slowly growing within the community - as well as my own newfound interested in some of Peat's ideas - some questions have been nagging at me.
For quite a while it's been clear that there is at least some link between dairy and bone disease. There's the correlative data showing the countries that consume the most dairy products have the highest instances of bone fractures and osteoporosis. And that cultures that have no history of dairy consumption have very low rates of these diseases.
Is it merely correlative? Is it the higher protein intake in general that is causing this? What about the more direct data showing that dairy causes the body to excrete calcium?
As I mentioned, I've been interested in aspects of a Ray Peat-style diet, but the heavy dairy focus has me hesitating.
Interested in all your thoughts!
And the populations that consume the most leafy greens (and minimal calcium) are shown to have the least incidences of bone fractures and osteoporosis. Yeah sure Vitamin D helps but Vitamin K (found primarily in leafy greens, other green vegetables, and avocados - see the green pattern here?) and saturated fats are extremely overlooked.
And here's how excess consumption of milk (calcium and vitamin D) actually promotes osteoporosis...
To save you the reading, from what I understood and using the best of my ability to explain to you how too much calcium is bad for your bones is;
disclaimer this is not exactly how it happens but just so you understand what's going on in a nutshell
Imagine your bones are cylinders. There is a tiny hole on the bottom and a tiny hole on the top. In one of the holes calcium goes in; the other, calcium goes out. When your bone needs calcium, it draws it in from the input hole. When that calcium gets used up, it moves it out to make room for new, fresh calcium to do its work. Now if you're consuming too much calcium, then you're clogging up the input hole. When the old calcium is no longer needed, it still gets dumped out but new calcium can't come in because you clogged the input hole.
again that's not the exact process but just so you can understand why too much calcium is bad for your bone health
Want stronger bones? Eat more Vitamin K. Saturated fats help as well. So I guess if you're worried about it, just make sure you're eating enough greenery to compensate for the excess amounts of calcium that your body doesn't need. Vitamin K helps metabolize the calcium in your blood.
I think correlative, and that protein intake is not the culprit either. I think Dragonfly makes a good point about the D, as D is necessary for proper Calcium utilization. The data showing that dairy causes the body to excrete Calcium makes sense if you can't use all the Calcium you are consuming. It would be interesting to see if cultures with history of vitamin D deficiency also share similar rates of those diseases.
I think people often look for reasons to vilify dairy and it's gotten a bad reputation because it is not well tolerated by some people. I agree with Peat/Roddy here; if you don't tolerate dairy, you're the problem, not the dairy. I think this can be for a number of reasons including vitamin D. Then you can get into reasons about why you're deficient in D, including deficiency in A, K, and Magnesium. Also to Tony's point they would both agree that there can be some problems with processed dairy, and I know Danny Roddy does raw dairy (which would help someone with lactose intolerance as raw milk has not had its lactase destroyed by processing). Danny has also written specifically about bone density, so his articles there may be of interest to you.
EDIT: Here is a great article about K by Masterjohn: http://www.westonaprice.org/fat-soluble-activators/x-factor-is-vitamin-k2 that discusses, among much else, bones and vit D.
I think it is simpler than all of that. Sedentary populations do not give the body the correct stimulus to maintain lean mass. This includes bone density. People sit on couches all day and watch TV. It does not matter how much nutrition is consumed, if the correct stimulus is not provided, the body will not increase lean mass. Populations from developing countries do not live sedentary lifestyles. Studies have shown that people who engage in strength training or activities that regularly require them to lift 'heavy' weights do not experience a decline in bone density.
To tie together what Tony and Dragonfly hinted at:
I propose that the issue is the synthesized versions of the fat soluble vitamins that are added back to processed, pasteurized, homogenized, and reduced fat milks.
(insert usual disclaimers about isolated high-dose studies, extrapolation from mice-studies, and so on)
Retinyl palmitate (synthetic vitamin A) specifically has been shown to increase risk of fracture, and generalized hypervitaminosis A (which is more likely if you're consuming fortified food sources) has been shown to break down bone and inhibit re-mineralization.
Also - milk is fortified with synthetic forms of D2, which have been shown to have no affect on fracture rates as well as a reduced capacity for raising plasma D levels. There are pretty much endless studies suggesting that the touted benefits of vitamin D aren't fully gleaned from supplementation of synthetic D2.
Couple that with the fact that calcium absorption is inhibited in vitamin D deficiency and the fact that if one is only eating processed, reduced fat versions of dairy products - they aren't going to be getting any vitamin K2, which is also vital to bone health.
It begins to look inevitable that, at the least, bone mineralization is going to be inhibited (if not bone resorption induced) by one (or all) of these deficiencies and imbalances in the complex nutrient interplay that is required to support our bones as the living organ that they are.
I see this as yet another example of our isolationist attitude towards nutrients; trying to pick and choose what we think causes the incredible synergistic benefit of a whole food product and reduce it down to a single supplement (calcium = bone health, what else could you possibly need to know?)