More than a bone story

Calcium is critical not just for the growth and maintenance of healthy bones and teeth, it’s also vital to proper functioning of the central nervous system

In fact, it is this role in the central nervous system that causes the body to strip calcium from the skeleton to maintain proper function when blood calcium levels are too low.

We know that calcium is critical to many physiological functions so it’s no surprise that things can go wrong when there are disturbances in calcium balance.Persistent excessive calcium in the blood has been linked to a number of negative health outcomes.On the other hand, low levels of blood calcium over time comes at significant cost to bone health.

Blood calcium is controlled within a very narrow range and complex mechanisms exist to deal with the day to day alterations in levels.

However, when the body needs to continually deal with excessive blood calcium, this can come at the expense of long term health.

 

 For many years, large rapidly absorbed doses of calcium have been associated with health issues such as kidney stones, milk alkalai syndrome (abnormally high blood calcium leading to deteriorating kidney function), and increased rates of cardiovascular disease in kidney dialysis patients.

Yet, despite the fact that the importance of the calcium balance is clear, and the negative health impacts of long term high blood calcium levels are well known, many of the supplemental calcium products available are still designed to be rapidly absorbed, or are marketed in “once daily” formats that deliver a large dose of calcium in a short space of time.

Now, a clear link has been demonstrated between calcium supplementation and increased risk of heart attacks, in otherwise healthy individuals. This is thought to be related to rapid spiking of blood calcium levels immediately following ingestion of the supplement 1 2 3 4

1.  Bolland, M.J., et al., Vascular events in healthy older women receiving calcium supplementation: randomised controlled trial. BMJ, 2008. 336(7638): p. 262-6.

2.  Bolland, M.J., et al., Effect of calcium supplements on risk of myocardial infarction and cardiovascular events: meta-analysis. BMJ, 2010. 341: p. c3691

3.  Bolland, M.J., 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. 342(d2040)

4.  Sambrook, P.N., et al., Does increased sunlight exposure work as a strategy to improve vitamin D status in the elderly: a cluster randomised controlled trial. Osteoporosis Int, 2012. 23(2): p. 615-24