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NEW YORK - Women who breast-feed may need to be careful about getting enough calcium to keep their teeth and gums healthy, new animal research suggests.

In experiments with rats, researchers found that lactating rodents were particularly susceptible to the effects of low calcium intake on the bones that support the teeth. Such bone-density loss can speed the progression of any existing gum disease.

Though the findings come from animals, they do suggest it's important for breast-feeding mothers to include enough calcium in their diets, lead researcher Dr. Kanako Shoji told Reuters Health.

Shoji and colleagues at Tohoku University Graduate School of Dentistry in Japan report the findings in the Journal of Periodontology.

During breast-feeding, a woman's calcium demands go up to meet her growing baby's needs, the researchers point out. In addition, certain hormonal changes during breast-feeding may contribute to bone-density loss.

So adequate calcium intake -- from foods like milk, cheese and fortified cereals and juice -- may become particularly important. The recommended calcium intake for women ages 19 to 50, breast-feeding or not, is 1,000 milligrams a day.

If a woman doesn't get adequate calcium from food, Shoji noted, supplements are an alternative.

For their study, the researchers fed lactating and non-lactating rats a diet with either adequate or low calcium levels. Periodontitis (a gum disease) was induced on one side of the animals' mouth.

The researchers found that all of the animals on the low-calcium diet lost bone density on the periodontitis-affected side of the mouth. However, the extent of the loss was greater in the lactating group.

In contrast, lactating rats that were fed enough calcium showed no such effects.

This, according to the researchers, suggests that if a woman gets enough calcium, breast-feeding may not be a risk factor for dental bone loss.

SOURCE: Journal of Periodontology, January 2007.