There have been several articles recently published in medical journals (JAMA, New England Journal of Medicine, British Medical Journal) about the possible risks associated with taking calcium supplements. The study groups are respected researchers, and include our own National Institute of Health. The studies addressed only the question of calcium supplements, and not the impact on health of a diet that was high in calcium.
I must state in advance that one problem with the results of the studies, besides their contradictory results, is that we have no good explanation for their results. While this does not mean the results are not valid and true, this lack of reasoning as to cause and effect makes it more difficult to believe in the result. It is also puzzling why the two main studies found different effects in men and women, and the results of one contradicted the results of the other.
The amount of calcium in your blood is very closely controlled by the body, and it is the ionized calcium, Ca++, a divalent cation that is the active form. Calcium exists in your blood both free as a cation and bound to serum proteins, and the aforementioned studies did not measure calcium levels. Because magnesium also exists as a divalent cation it often precipitates out in laboratory processes along with calcium, which led to the belief that the use of a supplement that contained magnesium as well as calcium was beneficial; no such result has ever been shown to be valid. However, since calcium is mildly constipating and magnesium is a mild laxative, combining the two elements into one pill makes theoretical clinical sense. Strontium is also a divalent cation, and unfortunately can be taken up by your bones along with calcium, which explains some of the bone marrow cancers induced by the radioactive strontium fallout from an atomic explosion.
The calcium levels are controlled by parathyroid hormone, which also activates Vitamin D into its useful form and thereby promotes the uptake of calcium by your bones both directly and indirectly. As a rule, the amount of calcium in your diet does not affect the level of calcium in your bloodstream. It is generally agreed that the calcium in your diet should contain between 600mg to 1200mg of calcium daily, along with 400 Units of Vitamin D, in order to maintain bone strength and prevent osteoporosis because activated Vitamin D promotes the absorption of calcium from your gut. We also know that ingesting too much calcium if you have chronic kidney disease can promote calcification of the arteries in your body, probably because kidney failure induces a state of secondary hyperparathyroidism, but a further discussion of this condition is beyond the scope of this article. Parathyroid hormone also increases the absorption of phosphate from your intestine which makes clinical sense since the largest mineral constituent of your bones is hydroxylapatite, which contains both calcium and phosphorous.
Now as to the studies. The question asked was whether or not taking calcium supplements (1000 mg or more in men and 1400 mg or more in women) had a benefit on the patient's health. One study showed an increase in overall mortality, and cardiovascular mortality as well as in heart attacks, but not in stroke. This increase in mortality was shown to exist in men, but not in women. Another study, published at about the same time, showed a similar increase in overall and cardiovascular mortality in women, but not in men(!).In each study the control group was same-sex patients who did not take calcium supplements.
So what are we to believe? There even are no clear-cut studies showing that calcium supplements prevent osteoporotic fracture; in fact some studies show an opposite result. (But taking extra Vitamin D at a dose of 800 mg/day does seem to prevent such fractures.) It is difficult to recommend calcium supplements in view of the above quoted data. It would be useful to have a study that measured calcium levels in people having heart attacks were it not for the fact that no one knows whether or not a MI acutely affects calcium levels. And it would seem heartless to tell the patients to read all three studies and to make up their own minds. I think that because no study showed by clear-cut evidence that taking calcium supplements was beneficial for one's health, then the recommendation of the doctor should come down on not recommending calcium supplements, thereby combining two tenets of medicine: "first, do no harm" and "less is more".
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If you Google USPSTF and calcium, you will find the latest recommendations for calcium supplements and Vitamin D issued on February 27 by the United States Public Service Task Force. The recommendations are confusing, so say the least. And they do not take into account the positive study showing the benefits of taking 800 Units of vitamin D.
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ReplyDeleteI seem to recall reading somewhere that measures of bone health in different countries are not directly correlated to the dietary calcium intake. If the supplemental calcium ends up in the wrong places, such as the arterial walls, it can do more harm than good. And dairy products, recommended as a source of calcium, can have their own problems.
It is simplistic and unscientific to expect the body's levels of calcium to respond to inadequate and unbalanced supplementation.
For one thing, 400 IU of Vitamin D per day is grossly inadequate. That recommendation is based on politics, not science. I take 5,000 per day. Sometimes more.
Half an hour of full body exposure in the midday mid summer sun will typically produce over 10,000. I think the body's UV exposure-vs-Vitamin D production curve is a more reliable guideline than those of a hospital-pharmaceutical-industrial complex that has a financial vested interest in perpetuating the chronic conditions and lifelong dependence on drug use caused by the pandemic of Vitamin D deficiency.
Vitamin K2 and magnesium are other critical factors which you did not mention. Calcium supplementation without proportional amounts of these two and Vitamin D is just plain nuts. Let's also not forget that bone remodeling and density improvement are highly dependent on the impact signals received by those mysterious little strain gauges that are built into the bones for some odd reason...
Speaking of the medical industrial complex, I think Karl Denninger, in his Market-Ticker blog, has some good entries about how the whole thing has evolved into a corporate crony capitalist protection racket that threatens to undermine the solvency of the US Government within the next few years. This is nothing new. And practicing physicians are among those being victimized. Eventual collapse of any racket is a mathematical certainty.
I meant to indicate that the above comment #2 was sent in by one of my readers, and does not necessarily correlate with all of my thinking.
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