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Is Calcium Safe - New Guidelines

A ten-year follow-up from the Multi-Ethnic Study of Atherosclerosis (MESA) released in October 2016 showed no increase in CVD risk associated with dietary calcium. In fact, those with a high dietary calcium intake suggested a protective effect from incident coronary artery calcium. On the other hand, the study did suggest a 22% higher risk of coronary artery calcification with those using calcium supplements. Over the years, there have been numerous studies showing a higher risk of cardiovascular disease in the presence of those who use calcium supplements, as well as many studies that have shown no association or inconclusive evidence.1

Because of conflicting information concerning the effects of calcium on vascular health, the National Osteoporosis Foundation (NOF) and the American Society for Preventive Cardiology (ASPC) assembled a group of experts to evaluate the scientific literature concerning the effects of dietary and supplemental calcium (either alone or in combination with vitamin D) on cardiovascular disease. They released a joint clinical guideline in October 2016.

The guideline recommendations are as follows:
  • Calcium from food sources is preferred
  • Supplemental calcium can be used if there is a low intake of dietary calcium
  • Discontinuing supplemental calcium due to safety concerns is not necessary and may be detrimental to bone health
  • Currently no biological mechanism supports an association between calcium and cardiovascular disease
  • The NOF and ASPC adopt the position that there is moderate quality evidence (B level) that calcium with or without vitamin D intake from food or supplements has no relationship (either beneficial or harmful) with the risk for cardiovascular and cerebrovascular disease, mortality, or all-cause mortality in generally healthy adults.
  • In light of the evidence available to date, calcium intake from food and supplements that does not exceed the tolerable upper level of intake (defined by the National Academy of Medicine as 2000 to 2500 mg/d) should be considered safe from a cardiovascular standpoint.2
The reviewers noted that they synthesized trials and cohort studies separately but based conclusions on the total body of evidence. A few trials and cohort studies showed increased risks of higher calcium intake. The risk estimates were small (±10%) and were not considered clinically important. Also of note is the fact that some of the trials that were reviewed were thought to have a moderate risk for bias.

Most of the trials found no significant connection between calcium and cardiovascular outcomes. One of the studies actually found lower cardiovascular and mortality risk in women who took more than 1000 mg of calcium supplements per day compared to those who did not take supplements.

Critics of the new guidelines point out that the guidelines were based on a meta-analysis of primarily observational cohort studies and did not include those studies with a specific calcium dose. Many also feel that there is inconclusive evidence concerning supplement use, considering the body metabolizes supplements differently than it does dietary calcium. For these reasons, further studies are needed. In the meantime, some cardiologists have noted that they will not be recommending or prescribing calcium supplements and are not sure whether or not to tell their patients who may be taking supplements to stop them.  
 
References
  1. Anderson JJ, Kruszka B, Delaney JA, et al.  Calcium intake from diet and supplements and the risk of coronary artery calcification and its progression among older adults:  10 year follow up of the Multi-Ethnic Study of Atherosclerosis (MESA).  J Am Heart Assoc 20161:DOI:10.116/jaha.116.003815.
  2. Kopecky SL, Bauer DC, Gulati M, et al.  Lack of Evidence Linking Calcium With or Without Vitamin D Supplementation to Cardiovascular Disease in Generally Healthy Adults:  A Clinical Guideline From The National Osteoporosis Foundation and the American Society for Preventive Cardiology.