The highest amounts of calcium intake increase the risk of fracture
Patients are often surprised to learn that osteoporosis is not a calcium deficiency disorder but rather a failure to maintain the microarchitecture of the bone of which the protein matrix is a critical component. Moreover, earlier posts on magnesium and calcium have document the pro-inflammatory potential of calcium supplementation. Now fascinating research just published in the British Medical Journal offers evidence that calcium above the lowest quintile does not improve the risk of fracture of any type, while the highest levels actually increase the risk of fracture. The authors set out to...
"......investigate associations between long term dietary intake of calcium and risk of fracture of any type, hip fractures, and osteoporosis."
They note that confusion regarding the issue of calcium requirements has been...
"...reflected by the wide range of daily calcium recommendations for individuals older than 50 years: at present 700 mg in the UK, 800 mg in Scandinavia, 1200 mg in the United States, and 1300 mg in Australia and New Zealand."
The authors investigated 61,433 women born between 1914 and 1948 for 19 years for correlations between dietary intake of calcium and fractures of any type, hip fractures, and osteoporosis. They took into consideration vitamin D consumption, hormonal status, and other pertinent biological and lifestyle factors including physical activity. Perhaps not surprisingly in light of other evidence that has emerged recently about calcium, their data challenges the conventional wisdom:
"These findings show an association between a low habitual dietary calcium intake (lowest quintile) and an increased risk of fractures and of osteoporosis. Above this base level, we observed only minor differences in risk. The rate of hip fracture was even increased in those with high dietary calcium intakes."
In others, amounts higher than the lowest level of calcium intake adequate to avoid gross insufficiency and compromised bone micoarchitecture there were not only no significant benefits, the highest levels of intake increased fracture risk. The authors comment:
"The present results may reflect a situation when a moderate intake of calcium* combined with adequate intake of other micronutrients is sufficient to meet the structural and functional demands of the skeleton. High levels of intake did not further decrease the rate of fracture, and might even increase the rate of hip fractures...Moreover, use of supplemental calcium has been associated with higher rates of hip fracture both in a cohort study and in randomised controlled trials...Furthermore, high calcium doses slow bone turnover and also reduce the number of active bone remodelling sites. This situation can lead to a delay of bone repair caused by fatigue, and thus increase the risk of fractures independent of bone mineral density."
*Their data indicate that a total dietary intake of 700 mg of calcium per day is sufficient to prevent fracture and osteoporosis. The authors conclude:
"Incremental increases in calcium intake above the level corresponding to the first quintile of our female population were not associated with a further reduction of osteoporotic fracture rate."
Considering that chronic inflammation can be a primary factor in causing loss of the protein 'scaffolding' of bone responsible for strength, resilience, and the matrix to which minerals attach, these findings invoke recollection of the recent evidence that calcium supplementation can increase the inflammation of cardiovascular disease. In case you missed it, a recent research paper published in the British Medical Journal follows up on earlier reports of this association. The authors' intent was...
"To investigate the effects of personal calcium supplement use on cardiovascular risk in the Women’s Health Initiative Calcium/Vitamin D Supplementation Study (WHI CaD Study), using the WHI dataset, and to update the recent meta-analysis of calcium supplements and cardiovascular risk."
The examined the data from a randomised, placebo controlled trial of calcium alone or with vitamin D in 36,282 postmenopausal women over seven years for myocardial infarction, coronary revascularisation, death from coronary heart disease, and stroke. The data told an interesting story:
"In the WHI CaD Study there was an interaction between personal use of calcium supplements and allocated calcium and vitamin D for cardiovascular events...Calcium or calcium and vitamin D increased the risk of myocardial infarction (relative risk 1.24 (1.07 to 1.45), P=0.004) and the composite of myocardial infarction or stroke (1.15 (1.03 to 1.27), P=0.009)."
Clinicians and patients need to appreciate that inflammation, a fundamental causal factor in both osteoporosis and cardiovascular disease, can be made worse by calcium supplements. The authors conclude:
"Calcium supplements with or without vitamin D modestly increase the risk of cardiovascular events, especially myocardial infarction, a finding obscured in the WHI CaD Study by the widespread use of personal calcium supplements. A reassessment of the role of calcium supplements in osteoporosis management is warranted."