 People growing up in the United States have been taught since childhood that bones are primarily made of calcium, that the best dietary sources of calcium are milk and other dairy products, and that consuming these in substantial amounts on a daily basis is necessary to build strong bones. This message, presented to us for decades by doctors, teachers, government agencies and countless advertisements, now resides deep into our national health psyche.
Are these claims and recommendations accurate and health-affirming? Does the peer-reviewed scientific literature offer strong support, mild support, or no support at all? If you aren’t sure, you are not alone.
Let’s look at the evidence.
First, we should stipulate the basics. It is undeniably true that dairy products contain substantial amounts of calcium (300 milligrams in a cup of milk or yogurt, 200 mg in an average portion of cheese). Second, it is true that the mineral content of bone is mainly comprised of calcium (along with phosphorus and other nutrients). Third, there is substantial documentation that building up sufficient bone mass in one’s early years provides crucial insurance against bone loss in later years. Just as saving up money in good times is a hedge against times of economic difficulty, building strong bones in youth means that some bone loss in later years can be handled without the risk of disabling fractures of the hip or other weight-bearing bones.
Does High Calcium Intake Lead to Strong Bones?
Putting these facts together, it would seem logical to assume that people who consume large amounts of calcium (from dairy products, supplements, or other sources) from childhood onward will have the best bone strength and in later years enjoy the greatest protection against osteoporosis-related fractures.
Scientific research has shown this to be untrue. Even more strangely, there is evidence that the opposite is true.
People in nations that have the highest dairy intake and the highest calcium intake have the highest osteoporosis-related fracture rates, not the lowest. This information has been available in scholarly nutrition research journals since at least the mid-1980s,1 and recent studies2 confirm the fundamental point. Moreover, the World Health Organization recommends a calcium intake that is around half of what the U.S. government recommends, for people not living in Western nations. Even for people in the West (whose diets are presumed to be high in meat and whose lifestyles are presumed to be low in exercise), the WHO recommends calcium intake (800 mg) at a level well below current U.S. recommendations (1000-1300 mg).
What are we to make of this? If you’re being exposed to this information for the first time, I understand that it may seem like I’ve just told you that the sky isn’t really blue or that ocean water is actually just fine to drink.
Extraordinary Evidence
There’s an oft-quoted adage in scientific circles, “Extraordinary claims require extraordinary evidence.” Therefore, in support of these assertions that may seem extraordinary, let me quote from a recent (mid-2008) issue of HEALTHBeat, an e-newsletter from a widely-respected source, the Harvard Medical School (free email subscription at HEALTHbeat@hms.harvard.edu):
“For years, high calcium intake has been portrayed as one of the best things you can do to prevent osteoporosis and related fractures. But when researchers started to crunch the data from large, prospective studies that followed people for many years, the benefits weren’t so clear-cut. These findings led to randomized trials of calcium to test what effect it might have on fracture rates. |
