Calcium pills could more than double risk of heart disease and death.

Taking calcium pills could more than double your risk of heart attack, a study published today in the British Medical Journal suggests. The risk of death from cardiovascular disease is doubled in women with high calcium intake who are also taking calcium enriched supplements.

There isn't a month goes by without publication of new research that demonstrates a link between some dietary factor or supplement and increased risk of cardiovascular disease and mortality. The information in the end I suspect is so confusing it is little wonder that for the most part it is ignored. It is the problem of information overload.

Nonetheless there are good reason for taking this new study seriously, not least because experts recommend a high calcium intake for women in middle age and increasingly people are turning to calcium supplements.

As a result more than 60% of middle-aged and older women in the USA now take supplements and it is estimated that up to 5 million people in the UK take them. What this study demonstrates is that more care should be taken in assessing the need for dietary calcium supplements.

Normally the level of calcium in the blood is tightly regulated and does not fluctuate with changes in dietary intake. What the authors of the study in today's bmj suggest is that this essential regulation may breakdown due to calcium overload if calcium supplements are taken over long periods. The mechanisms regulating calcium in the body become disturbed.

Calcium is important for a variety of functions in the body. Indeed there is no function in the body for which calcium at some stage or other is not essential. It is involved in the beating and contraction of the heart, the function of skeletal muscle and of the brain, and also in the secretion of hormones from glands. It is essential at the very start of embryonic life and the fertilisation of the egg.

A healthy balanced diet should provide all the calcium we need. But there are times when this might have to be supplemented. To maintain constant concentrations of calcium in blood, muscle, and body fluids the body uses bone tissue as a reservoir. Some 99% of the body's calcium is stored in our bones. But this balance changes with age.

As we get older the balance of bone loss and reformation deteriorates. As a result the bone becomes less dense and more fragile. This is particularly so in post menopausal women with the risk of osteoporosis. Women with osteoporosis have lower total-body calcium levels

Blood calcium is regulated by two hormones: parathyroid hormone and calcitonin produced by the thyroid and parathyroid glands. If calcium falls, parathyroid hormone stimulates the release of calcium from bone into the blood. When calcium levels return to normal parathyroid hormone levels fall. If the levels of calcium in the blood get too high, the thyroid gland releases calcitonin which decreases the calcium released from bones. Some people have medical conditions that cause the glands to continuously release parathyroid hormone, which causes the bones to constantly release calcium.

Other recent trials have indicated a higher risk of ischemic heart disease and stroke with calcium supplements, but these findings have not been demonstrated consistently. In the newly published study, researchers from Uppsala University in Sweden studied 61,443 Swedish women (born between 1914 and 1948) for an average of 19 years to test this association.

Women who had a higher dietary intake of calcium exceeding 1400mg/day and who also used supplements had a higher death rate compared to those not taking supplements. Women with a high dietary calcium intake (>1400 mg/day) were more than twice as likely to die compared with women with a 600-999mg/day calcium intake.

The researchers explain their findings by suggesting that diets either very low or very high in calcium can override normal homeostatic control causing changes in blood levels of calcium. Adults require approximately 1,200 mg of calcium every day. With balanced healthy diet calcium supplements should be unnecessary, and where calcium balance is disturbed, then the underlying causes should be investigated and treated.

The researchers conclude that high calcium is associated with “higher all-cause and cardiovascular mortality rates”. The take home message is that to prevent fractures in the elderly emphasis should be placed on individuals with a low intake of calcium rather than increasing the intake of those already consuming satisfactory amounts in their diet.

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