Public health experts have long known that breastfeeding is the best way to give a baby important nutrition and health benefits. Now a new study shows that breastfeeding may also benefit the health of the mother. The study shows that nursing a baby reduces a woman's risk of developing diabetes.

Alison Cape is a new mother who has been nursing her baby Charlotte since she was born nine weeks ago.

"I'm planning on breastfeeding until I can't do it any longer, which, I'm hoping to go for a full year, but as I work, you know, I'll go for as long as I can," she said.

If Ms. Cape does breastfeed for a full year, she could dramatically reduce her risk of diabetes. That is the finding of a new study in the Journal of the American Medical Association by Dr. Alison Stuebe and her colleagues at Brigham and Women's hospital in Boston. The researchers came to their conclusion after tracking the health and breastfeeding practices of more than 150,000 women for 15 years after they had their last baby.

"We found that breastfeeding is really good for mothers," said Dr. Stuebe. "Each year a woman breastfed reduced her risk of diabetes by 15 percent. A woman has two children, she breastfeeds for two years. Our data suggest that she may reduce her risk of diabetes by nearly a third."

The Boston researchers say it matters how intensely a mother breastfeeds. Women who exclusively breast fed, giving their babies nothing but breast milk, saw a greater health benefit than those who fed their infants breastmilk and formula or food.

Conversely, Dr. Stuebe and her colleagues found that artificially suppressing a woman's lactation by drugs increases her risk of diabetes.

How is breastfeeding connected to diabetes? It could be because it can help prevent weight gain, a leading risk factor for the disease.

"A breastfeeding woman uses up about 500 calories a day making milk for her baby," said Dr. Stuebe. "That's the equivalent of running about four to five miles [six to eight kilometers] a day. That's a lot of energy."

Alison Cape says the study convinces her to stay the course.

"It's just another incentive for people to keep breastfeeding and it certainly reinforces my decision to do so," she said.