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Sunday, 5 November, 2000, 01:02 GMT
Calcium vital during pregnancy
Cheese is source of calcium
Scientists have uncovered evidence proving just how important it is for women to consume sufficient levels of calcium during pregnancy.

A team from the University of North Carolina at Chapel Hill found pregnant women who do not consume enough calcium in their diets or through supplements run a risk that their bones will start to break down and release potentially harmful substances into the blood.

The researchers found pregnant women with low calcium levels have a higher level of lead in their bloodstream than pregnant women with normal calcium levels.

The protective effect of calcium became stronger as pregnancy progressed

Professor Irva Hertz-Picciotto, University of North Carolina at Chapel Hill
Most of the body's lead - some 95% - is contained in bone tissue.

Therefore, high levels of lead in the bloodstream is an indication that bone is breaking down, or demineralising, and thus releasing locked-up lead supplies.

The researchers discovered lead is more likely to be released into the blood during the second half of pregnancy.

They are concerned it could damage both the mother and her developing foetus.

Lead researcher Professor Irva Hertz-Picciotto said: "Past research has linked lead to many adverse conditions, including nervous system and possible cardiovascular problems."

Prof Hertz-Picciotto stressed the levels of lead found were still relatively low.

"We are still trying to determine whether there are health effects from these low levels."

Blood samples

The study involved 195 women who entered prenatal care at Magee-Women's Hospital in Pittsburgh, Ohio between 1992 and 1995.

Pregnant woman
Good diet is important during pregnancy
Using a technique called atomic absorption spectrophotometry, researchers analysed up to five blood samples from each woman for lead during their pregnancies and took extensive patient histories.

Prof Hertz-Picciotto said: "We found not only that calcium intake at the recommended daily allowance level protected somewhat against lead, but also that higher calcium levels corresponded with even less lead.

"The protective effect of calcium became stronger as pregnancy progressed."

The blood lead levels of older mothers increased more during pregnancy compared with younger mothers.

The researchers suggested that was because older mothers had accumulated more lead in their bones, particularly in the 1960s and 1970s when leaded gasoline was still used in automobiles.

Age and calcium had combined effects. From week 20 to week 40, for example, blood lead levels in pregnant women with low calcium intakes increased 25% at age 18, 37% at 23, 65% at 33 and 99% at 43.

Pregnancy and the first four years after menopause are periods when women's bones are most likely to undergo demineralisation.

Sarah Schenker, a dietician at the British Nutrition Foundation, said it was important for all young women to consume sufficient levels of calcium.

She said: "Women lay down the majority of their bone mineral density in their late teens and early twenties.

"Once that period is over it is very difficult to redress the balance, and if you have not laid down calcium during that period then you are at greater risk of brittle bone disease."

The research is published in the Journal of Epidemiology.

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