Calcium supplements: helpful in moderation, harmful in excess

BMJ Group News

Calcium is important for strong bones, but taking too much with high-dose supplements can lead to serious health problems, such as high blood pressure and even kidney failure. Calcium overdose has become more common in recent years, according to a new report. However, the researchers stress that calcium supplements should be safe when taken at recommended doses.

What do we know already?

Calcium and vitamin D are the most important nutrients for building your bones and keeping them strong. If you don't get enough, you have an increased risk of developing osteoporosis, a condition where your bones are so weak that they break easily.

Milk and other dairy products, green leafy vegetables, and fish with edible bones are excellent sources of calcium, and our bodies produce vitamin D in response to sunlight. But many older people - particularly women past the menopause -don't get enough of these nutrients and need to take supplements. This is partly because their bodies don't absorb calcium as efficiently as they used to.

Studies show that taking supplements with calcium and vitamin D may help prevent osteoporosis and lower the risk of broken bones. So, not surprisingly, many people routinely take these supplements. However, some take much more than the recommended dose, not realising that ingesting too much calcium can lead to a potentially serious condition known as milk-alkali syndrome.

You get this syndrome if you consume substantially more calcium than your body needs, leading to high levels of calcium in your blood (called hypercalcaemia). This can cause serious problems, such as high blood pressure, kidney damage, and even kidney failure.

What does the new article tell us?

In the new report, researchers looked at the history of milk-alkali syndrome and also its recent resurgence.

The syndrome first appeared in the early 1900s after a US doctor named Bertram Welton Sippy introduced a special diet (known as the Sippy diet) for people with peptic ulcers. The diet involved consuming large amounts of milk, cream, eggs, and cereal, as well as antacid powders every half hour. This bland diet helped soothe ulcer flare-ups. But its exceptionally high milk content meant that many people ingested too much calcium - hence the name milk-alkali syndrome.
With the development of effective drugs for ulcers, use of the Sippy diet declined and so did rates of milk-alkali syndrome. But the syndrome became more common again in the 1990s, due in large part to widespread use of over-the-counter calcium and vitamin D supplements.

The syndrome is now the third most common cause of high blood calcium levels, say researchers, accounting for between 8 percent and 38 percent of all hospital admissions due to hypercalcaemia in the US. (High blood calcium levels are also frequently caused by thyroid problems and cancer.) And, today, older women rank among those most often affected by the syndrome, rather than men with ulcers as in the past.
Since the syndrome is now typically tied to calcium supplements rather than milk consumption, researchers say its name should be changed to 'calcium-alkali syndrome'.