What Calcium Means for Your Heart
Why are we advised to take calcium supplements?
Men and women are advised to take calcium because it has been shown to reduce blood pressure a small amount (2-3 mmHg). Women, in particular, can stall the deterioration of bone strength (demineralization) by taking calcium supplements, 1200-1300 mg per day, and eating calcium-rich foods like dairy products.
Is that all true?
It is true insofar as we remain vitamin D deficient. In other words, decades of clinical studies that examined the benefits of calcium supplementation did not first correct vitamin D deficiency. For most of us without vitamin D supplementation, deficiency is the rule.
Think of vitamin D as the master controller over calcium metabolism: How and what happens to calcium is determined, to a large degree, by vitamin D. A funny thing happens when you fully replete vitamin D: Intestinal absorption of calcium as much as quadruples. That means your body will efficiently absorb the calcium in broccoli and spinach.
Is it still necessary to force-feed your body mega-doses of calcium once vitamin D has been repleted? I don't think so.
While the evidence is indirect, several observations point towards the lack of necessity, perhaps even the danger, of calcium supplementation at high doses once vitamin D is addressed. For instance:
- Women who take calcium, 1200 mg per day, with vitamin D, 800 units per day, double their five-year risk for heart attack, according to a New Zealand study. The highest risk were among the women who most reliably took calcium.
- Men who take calcium, 1200 mg per day, with vitamin D, 800 units per day, also may substantially increase heart attack risk.
- Most clinical studies have examined calcium supplementation with low doses of vitamin D (e.g., 200-800 units per day), and it is therefore difficult to separate the effects of the two. However, my experience and that of many vitamin D advocates suggest that bone density increases more with vitamin D alone when true restorative doses are used, and that little or no calcium is necessary to increase bone mineralization.
- Calcium suppresses parathyroid hormone, PTH. That is, in fact, how calcium stalls (usually does not reverse) bone mineral loss─not by adding calcium to bone, but by suppressing PTH release. (PTH causes bone demineralization.) Vitamin D suppresses PTH to a far greater degree than calcium.
What is needed is a broad reconsideration of the advice to take calcium. In an age when more and more people are appreciating the power of vitamin D supplementation to achieve normal blood levels, there may be danger ahead for those who fail to address their calcium "overdosing."
This means that the last 20 years of clinical studies on calcium supplementation may be rendered irrelevant in an age of full vitamin D restoration. While low-dose calcium supplementation may be helpful, our old advice to supplement 1200-1300 mg per day may no longer be valid.
I've been telling my patients that, until clarification is obtained with clinical studies, to take no more than 600 mg of calcium per day if vitamin D has been restored to 60-70 ng/ml of 25-hydroxy vitamin D.
Check out Dr. Davis's last article on calcium: