Vitamin D and Calcium Conundrum


Vitamin D and calcium are unquestionably related.  The vitamin is required for the absorption of calcium from the digestive tract.  But they are related in another way as well.  There is great confusion about whether to take supplements of either,and if so, how much.  Calcium is the one of greater concern because of a possible link between supplements and heart attacks.  With vitamin D, risks are minimal, it is more a question of whether supplements are needed. 

A recent large study followed close to 24,000 people in Germany aged 35 to 64 for some 11 years and compared the health of subjects taking calcium supplements to those who were not taking any.  There was a statistically significant association between calcium supplements and heart attacks, with people taking supplements having roughly twice the risk.  Newspaper headlines about calcium supplements doubling the risk of heart attack caused panic.  While there is no need for panic, the data should not be swept under the carpet.

Out of the 24,000 subjects only 354 had heart attacks, so we are not talking about a large risk.  But what is noteworthy is that there were proportionately more in the supplement group.  No such relationship existed when only dietary calcium was taken into account.  The thinking is that calcium supplements cause a spike in the blood levels of calcium which may be a problem whereas calcium from the diet is absorbed at a more even rate.  In science one never makes major decisions based on one study, but this is not the first time that calcium supplements have been linked with heart attacks.  Of course risks have to be weighed agiants benefits.  And this is where we run into a problem because the benefits of calcium supplements may not be as great as has been assumed. 

A U.S. government panel has just concluded that there is no value in postmenopausal women taking supplements of calcium up to 1000 mg a day coupled with up to 400 IU of vitamin D.  The conclusion was mostly based on the Women’s Health Initiative, a study of more than 36,000 women who took either 1000 mg calcium with 400 IU of vitamin D or a placebo in a randomized fashion.  There was no difference in hip fractures or total fractures compared with placebo.  Critics have said that 400 IU of vitamin D is not enough and that the control group already had a sufficient dietary intake of calcium.  Indeed it is possible that if vitamin D were increased to 1000 IU a difference would be noted.  So the fact is that the jury is out on whether calcium supplements are beneficial or not.  If they are beneficial, they are in a minimal way otherwise there would be no argument. 

As far as vitamin D goes, the upside is brighter.  There are all sorts of studies associating the vitamin with improved immunity, reduction in cancer risk, reduction in heart disease risk, reduction in the risk of diabetes and reduction in the risk of neurological diseases such as MS.  At the doses commonly taken there appears to be no risk.  Much was made of a study from Denmark that found a greater risk of death both from low blood levels of vitamin D and high levels during a three year observation period.  But one would have to take huge doses of vitamin D, something like 5000 IU a day, to fall into the overdose level.  So the bottom line at this point is that anywhere from 400 to 1000 IU of vitamin D a day is likely to be beneficial and presents no risk, while the calcium supplement issue needs more work.  Basically, nobody has a clear picture of calcium supplementation.  The most we can say is that it is better to meet our calcium needs from the diet than from supplements.  And don’t forget the weight bearing exercise.

 

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Print | posted on Wednesday, June 27, 2012 2:16 AM

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