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Friday, March 8, 2013

High Calcium Intake may not be Good, Rather may Increase ALL Cause Mortality

Posted by Prahallad Panda on 9:17 PM Comments

In Sanskrit there is an proverbial advice, "Ati Sarbatra Gahirtam"; that means, 'Too much of anything is bad". Also there a similar, but more elaborate proverbial advice, "Jala gahale srusti nasa and jala bihune srusti Nasa"; that means, if there is excess of water there is destruction also same happens in absence of water, something like famine and flood.
As we know calcium is a vital mineral for functioning of our system, from muscle contraction to keeping bone stronger. People start taking it in the faith that it will improve health; or at least keep them fit for work.
Now, in a study of women in the Swedish mammography cohort, it was seen that a high calcium intake (>1400 mg/day) was associated with an increased rate of mortality, including death from cardiovascular disease. 
The increase was moderate with a high dietary calcium intake without supplement use, but the combination of a high dietary calcium intake and calcium tablet use resulted in a more pronounced increase in mortality. For most women with lower intakes we observed only modest differences in risk.
Possible cause can me:
Calcium levels in serum are under tight homeostatic control, and calcium intake is not normally correlated with calcium serum levels. Diets that are low or very high in calcium can, however, override normal homeostatic control causing changes in blood levels of calcium or calciotropic hormones. 
Calcium enriched meals can reduce calcitriol, the active vitamin D metabolite, by inhibition of 1α hydroxylase and also increase serum levels of fibroblast growth factor. Higher levels of circulating fibroblast growth factor 23 are associated with an increased risk of cardiovascular events and all cause mortality.
English: Overview of calcium regulation (See W...
English: Overview of calcium regulation (See Wikipedia:Calcium in biology). To discuss image, please see Talk:Human body diagrams References Page 1094 (The Parathyroid Glands and Vitamin D) in: Walter F., PhD. Boron (2003). Medical Physiology: A Cellular And Molecular Approaoch, 1300, Elsevier/Saunders. (Photo credit: Wikipedia)

In addition, fibroblast growth factor 23 downregulates calcitriol levels. Vitamin D suppression leads to an upregulation of the renin-angiotensin-aldosterone system and hypertension, higher levels of proinflammatory cytokines involved in the pathogenesis of atherosclerosis, increased carotid artery intima medial thickness, decreased endothelial function, hypertrophy of cardiac and vascular muscle cells, and a possible increase in serum triglycerides. Finally, high serum calcium levels can increase the risk of cardiovascular mortality by induction of a hypercoagulable state.
Emphasis should be placed on people with a low intake of calcium rather than increasing the intake of those already consuming satisfactory amounts.
When looking at the totality of our data, high calcium intakes were associated with higher rates of death from all causes and cardiovascular disease. Mortality was not increased between 600 and 1400 mg/day of total calcium intake, the most customary levels of intake in this setting. 

In summary,
  • A low calcium intake is associated with higher fracture rates in elderly people and a higher risk of stroke and fatal ischaemic heart disease
  • Meta-analyses of some randomised studies have, however, shown a higher risk of incident ischaemic heart disease and stroke with calcium supplement use
  • In observational studies, use of calcium supplements has been associated with both lower overall and cardiovascular mortality rate, as well as higher incidence of cardiovascular disease.
  • In this Swedish cohort study of women, high intakes of calcium (>1400 mg/day) were associated with higher mortality
  • The increase was moderate with a high dietary calcium intake without supplement use, but more pronounced with a high dietary calcium intake with calcium tablet use.
  • Mortality was not increased between 600 and 1400 mg/day of total calcium intake, the most customary levels of intake in this setting. 
  • For most women with lower calcium intakes only modest differences in risk were observed.

The original article published in the BMJ may be accessed here.
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