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1000 on Ca+ only-->6 more MI's or strokes and 3 less fractures

a previously reported 30% risk of MI w calcium supp extends to people who are also taking vit D
often taken in combination: Calcium and vitamin D, for bone health
causes a roughly 20% increased risk of both MI and stroke

new study is published online April 19, 2011 in BMJ
Dr Mark Bolland (University of Auckland, New Zealand)
WHI study showed no CV risk with calcium, vitamin D

previous meta-analysis highly controversial
looked only at patients taking calcium alone compared with placebo
or people taking calcium and vitamin D compared with people taking vitamin D alone
was at odds with a Women's Health Initiative (WHI) study that showed no adverse CV effects w these supps

confounder: in WHI women already taking ca&vitD were told not to stop even if randomized to placebo, 54% already taking calcium, 47% taking vitamin D at the time of randomization, patient group "contaminated"

Dr Ian Reid (University of Auckland), senior author on the new BMJ study
requested pt level data in order to correct for the confounder

17 000 women not taking supps but put on them-->statistically sig incr in risk of "clinical MI"
(hazard ratio 1.22; p=0.05)
and clinical MI and stroke (hazard ratio 1.16; p=0.05)

women already taking supplements at baseline, no such spike in events was seen

this data added in as well as two other studies not included in previous meta-analysis n=12,000
new n= almost 30,000

use of calcium or calcium plus vitamin D significantly increased both risk of MI and composite of MI/stroke
at both patient-level data and trial-level data
risk of stroke was significantly increased in the patient-level data

small levels of supplemental calcium create "abrupt" increases in blood calcium levels within hours
one criticism of group's earlier work: CV events occurring too swiftly to be related to calcified plaques
stroke events mbdt longer-term process of calcium accruing in the vessel walls
MI spikes may reflect more acute response to blood ca levels, plt fx change, coag change, EC activity change

CV effects of Ca are "modest"
25%-30% for MI and 15%-20% for stroke
1000 on Ca+ only-->6 more MI's or strokes and 3 less fractures
NNTH = 178 for cv consequence, 302 for prevention of fracture
*docs should look at other options for bone health
getting Ca+ from diet doesn't seem to have same risk

other studies showing that use of calcium and vitamin D on top of bisphosphonates for osteoporosis have in the past been "reassuring" on CV safety


Bolland MJ, Grey A, Avenell A, et al. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women's Health

Initiative limited access dataset and meta-analysis. BMJ 2011; DOI: doi:10.1136/bmj.d2040. Available at: http://www.bmj.com.

Bolland MJ, Avenell A, Baron JA, et al. Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: Meta-analysis. BMJ 2010; 341:c3691.

Abrahamsen B, Sahota O. Do calcium plus vitamin D supplements increase cardiovascular risk? BMJ 2011; doi10.1136/bmj.d2080. Available at: http://www.bmj.com.


( 5 comments — Leave a comment )
Apr. 22nd, 2011 06:42 pm (UTC)
I've seen various articles on this and it's confusing. I take calcium supplements for muscle cramping. Am I setting myself up for other, more serious, health risks?
Apr. 22nd, 2011 07:02 pm (UTC)
The data is not so strong as to suggest that nobody should take calcium supplements. It is true that if you have higher calcium levels you are more likely to develop hard atherosclerotic plaques. This study also suggests that when people start taking calcium they have an increase in MI's that must be due to increased calcium levels in the blood, not atherosclerosis. In general you need to manage your cardiovascular risk in about 100 ways. The best time to take calcium so that you integrate it into bone is at bedtime. I'm sure there will be more to know about this......and this info needs to be taken in the greater context.
Apr. 22nd, 2011 07:13 pm (UTC)
And... what is an MI?

I'm more concerned with muscle function than bone, so take my calcium/magnesium/Vit D with food (as suggested by you). I used to take it all at bedtime but changed that habit several months ago and I think my results are better.

Re: Edit: I dunno why I put YOU in all caps! :)

Edited at 2011-04-22 07:14 pm (UTC)
Apr. 22nd, 2011 07:19 pm (UTC)
MI = myocardial infarction = heart attack

It's complicated! Vit D isn't absorbed if you don't take it with something fatty. Calcium is best taken in many small doses throughout the day, because it is hard to absorb. Magnesium is relaxing and vasodilating and helps with sleep. And there is 100x more to know and I have to go! Sorry I can't give you a firm and permanent final answer. Everything is a balance of competing concerns and depends on the individual patient so don't get all freaky about science. OK?
Apr. 22nd, 2011 07:22 pm (UTC)
Eh, I'm not getting all freaky, I think I finally got over that. I take what comes and go with the flow, for the most part. I'm doing what works best for me, but new information is always welcome!

Have a good one.
( 5 comments — Leave a comment )



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