Milk, Does It Do A Body Good? Part 1: Calcium and Osteoporosis
Posted May 08 2008 11:34am
We’ve all seen the advertisements, from the It Does A Body Good commercials to the Got Milk? campaign. It’s been drilled into our heads, over and over again, that milk is absolutely essential to the body. If you’re young, you need the protein, vitamins, and minerals for growth. If you’re not young, you need the calcium to protect your bones against osteoporosis. In this series, I want to examine the good and the bad of dairy consumption. I’m going to break the dairy debate down into five posts:
Calcium, Bone Health, and Osteoporosis
Other Possibly Detrimental Components
Raw vs. Pasteurized/Homogenized
My Take On The Whole Ordeal
Calcium, Bone Health, and Osteoporosis
Tell someone that you don’t consume dairy products and the immediate question is “Where do you get your calcium,” the implication being that your bones are going to crumble under their own weight without the calcium that the dairy industry tells you is so important. So what’s the big deal about this “calcium” anyway?
Calcium (chemical symbol CA) is the fifth most abundant element by mass in the crust of the Earth. It’s also the most abundant metal by mass in animal bodies, accounting for 1-2% of body weight, most of this in the teeth and bones.(1) Along with potassium, calcium plays a role in proper metabolic function, cellular permeability, and electrical conductance in your nerves. Muscle contractions, nerve impulses, and properly functioning glands and blood vessels, along with blood clotting, are all functions of calcium-potassium channels. Needless to say, calcium is an important element in the body.
Calcium is also one of the three main building blocks of your bones, a point that the marketing firms behind the dairy campaigns are sure to drive home. The other two dietary building blocks are vitamin D and magnesium. And of course, given the “Use It or Lose It” attitude your body brings to the party, weight-bearing activity is necessary to maintaining bone strength. Your bones aren’t just sticks on which to hang skin and hair. They are living pieces of the body, constantly being torn down and rebuilt, luckily in very small sections rather than wholesale.
So there’s no question that calcium is essential to the body. But how much calcium do we need? World’s Healthiest Foods suggests:(3)
Most men should aim for 1000-1200 mg daily, young women for 1000-1300 mg daily, and postmenopausal women for 1200-1500 mg of calcium daily.
Another answer to that question, and one I am more inclined to believe, comes from the work of Dr. Loren Cordain. While I can’t find an exact range, I recall that daily intake for hunter-gatherer tribes was in the 300-600mg/day range. Perhaps someone with The Paleo Diet book can give me an answer from the book. Obviously, our ancestors must have had weak bones since they had such a low calcium intake.
But wait…something doesn’t add up. The United States has a very high consumption of dairy products and calcium, yet it also has one of the highest rates of osteoporosis, while hunter-gatherers were known to have quite robust bones. What gives? The problem is that, contrary to what the dairy industry tells us, there is far more to the equation of bone health than just calcium. Those other pieces of the equation, vitamin D and magnesium, are as important, if not more important to bone health. For instance, hunter-gatherers typically had a 1:1 ratio of calcium to magnesium. Today, it’s more like 4-to-1.(5)
Could too high an intake of calcium actually exacerbate the issue? Would I have asked the question if the answer wasn’t “Yes”? Calcium and magnesium compete for the same absorption channels, so too much of one will preclude the other from being properly absorbed.(5)
High dietary calcium can cause magnesium deficiencies, even when normal levels of magnesium are ingested
And of course, most people are also not eating enough of the right foods for sufficient magnesium intake: nuts, seeds, green leaves, certain fishes. So we take in too much calcium and not enough magnesium.
Now we know that too much calcium is a problem. What about the vitamin D variable in this equation? Well, when it comes down to it, vitamin D is necessary for proper absorption and retention of calcium. And where do we get vitamin D? The most prevalent source is our skin, but that requires UVB rays to help the body synthesize the vitamin from cholesterol. We all know that we shouldn’t get any sun though because that’ll cause skin cancer (please note the biting sarcasm here). Other sources of vitamin D are foods that few people eat enough of: eggs, liver, fish, oysters. Eggs are too high in cholesterol, liver is scary, fish tastes “too fishy,” and oysters are like snot. Of course, I only agree with the last one there, but that seems to be the general consensus. Dairy products are fortified with synthetic vitamin D, but you all know how I feel about foods that have to be fortified to have enough of something. If it requires fortification, it’s not a good source for that vitamin.
Vitamin D may actually be more important than calcium. Studies have shown that vitamin D protected women against hip fractures even when milk and high intakes of calcium didn’t.(6) Vitamin K also plays a role in bone health, helping to produce bone-building proteins and inhibiting production of substances that break down bone. But both vitamin D and vitamin K are fat-soluble vitamins and we know that fat should be avoided. Of course, this is a cursory overview of the vitamins and minerals involved in bone health, but it’s illustrative. Others such as potassium also play a role, but are unimportant to our discussion of dairy. Contrary to popular opinion, higher protein intake also appears to be beneficial to saving your bones.
So when you couple too much calcium and not enough magnesium with deficient levels of vitamins D and K and a mostly sedentary lifestyle, what do you get? “Weak bones” is the proper reply. But for some reason the dairy industry isn’t telling us that part. There are two other interrelated components to this debate as well: acid-base balance and calcium balance. Acid-base balance is a measure of the net renal load of the foods you eat.(8) Some foods break down as acid-forming compounds, namely animal products and grains. Other foods break down as base-forming compounds, such as fruits and vegetables. Fats are mostly neutral. Since few of us question the benefits of meat, fruits, or vegetables, that leaves grains and dairy as the dietary components in question.
Moving along, the body works to maintain a very tight balance on the pH of the body. If there are too many acid-forming foods in the diet, the body must use a base to neutralize the acid. Your bones are the largest deposits of alkaline material in the body. I’m talking specifically about the calcium in your bones. So if you eat a diet high in meat, grains, and dairy and low in fruit and vegetables (anyone seeing a Western dietary pattern here?), you have a net acid-forming diet, which will cause the body to scavenge calcium from the bones. This leads directly into the discussion of the calcium balance.
Which is better, a calcium intake of 300mg/day or 1500mg/day? The correct answer is “C) There is not enough information to answer this question.” To answer the question, we need to know what the calcium outflow is. If the body in question for the first choice only has a daily requirement of 250mg of calcium while the second body is in need of 1700mg due to the dietary factors we’ve discussed, who is better off? It’s all about balancing the see-saw, not just getting as much calcium as possible. Other factors increasing the need for calcium are smoking, too much alcohol, and too much salt.
Looking at the big picture, it appears that a moderate calcium intake is a necessary, but not sufficient, condition in building strong bones. However, dairy is not a necessary component in the equation because calcium is available from so many other sources: kale, almonds, sardines and canned salmon with bones, oranges, broccoli, sweet potatoes. In fact, one study showed that the calcium in kale is better absorbed than that in milk.(9) Note that the mean absorption for dairy was only 32% (that for kale was 40%). Of course, the total calcium content of the milk is far higher, but the point is that the acidic nature of milk may not lend itself to proper calcium assimilation.
When all of this is put together, does anyone think that more milk is the answer to keeping your bones strong? It sounds to me like the proper answer is to eat a more alkalizing diet, meaning that at the very least grains have to go, in favor of fruits and vegetables, along with getting plenty of vitamins D and K and magnesium. Moving about here and there wouldn’t hurt anything either.