London: Intake of too little dietary calcium increases women`s risk of a thyroid condition that can cause bone fractures and kidney stones, scientists claim.
Researchers found women with the highest intake of dietary calcium had a 44 per cent reduced risk of developing primary hyperparathyroidism (PHPT), compared with the group with the lowest.
They suggest increasing calcium intake cuts the risk of the disease, the `BBC News` reported.
Milk and other dairy foods, nuts and fish such as sardines and pilchards (where the bones are eaten) are some dietary sources of calcium.
However, taking too much could cause stomach pains and diarrhoea.PHPT is caused by overactive parathyroid glands secreting too much parathyroid hormone.
The US team from Brigham and Women`s Hospital looked at 58,300 women who were taking part in a much broader ongoing piece of research called the Nurses` Health Study.
All were aged between 39 and 66 in 1986, when the study began, and had no history of PHPT.The women were given food questionnaires to record how frequently they ate particular foods or supplements, including calcium, every four years, with the latest being completed in 2008.
Over that 22 year period, 277 cases of PHPT were confirmed.
PHPT affects around one in 800 people during their lifetime and is most common in post-menopausal women.
"Increased calcium intake, including both dietary and supplemental calcium, is independently associated with a reduced risk of developing primary hyperparathyroidism in women," researcher Dr Julie Paik, said.
The study was published in the British Medical Journal.