MONDAY, March 1, 2004 (HealthDayNews) -- Evidence that breast-feeding has long-term health benefits keeps mounting, and now a new study shows it may also permanently lower children's blood pressure.
"Breast-feeding is very important, because how babies are nourished in the womb and in the first years after birth can permanently affect how their organs grow and function," says Dr. Nancy E. Wight, a neonatologist at Children's Hospital and Health Center and Sharp Mary Birch Hospital for Women in San Diego.
For example, it is known children who were breast-fed have fewer strokes, less heart disease and are also less likely to be obese as adults than are children who were not nursed, she adds.
In addition, nutrition in early life may determine metabolism, insulin output and liver function, Wight says. "Not breast-feeding carries with it significant adult health risks," she adds.
In the new British study, researchers collected data on 4,763 children who participated in the Avon Longitudinal Study of Parents and Children. The team, led by Dr. Richard M. Martin, a senior lecturer in epidemiology and public health at the University of Bristol, compared the blood pressures of bottle-fed children and breast-fed children.
At the time of the study, the children were about 7 years old. Martin's group asked mothers to provide data on how they fed their children when the kids were 6 months and 15 months old, according to the report in the March 1 online issue of Circulation.
"We found that there was a small reduction in blood pressure among the children who were breast-fed as infants," Martin says. These children had about 0.8 millimeters of mercury lower systolic blood pressure (the upper figure in a reading) and a 0.6 millimeters lower diastolic pressure (the bottom) compared to children who were bottle-fed, he says.
The researchers also found the longer babies were exclusively breast-fed, the greater the reduction in blood pressure. They note that for every three months of breast-feeding, there was a 0.2-millimeter drop in systolic blood pressure.
The child's sex, weight or pulse did not affect the difference in blood pressure. In addition, family social status, income, number of brothers and sisters, the mother's alcohol consumption, the child's health and the child's ethnicity were not factors.
"There appears to be something about breast milk that actually causes a reduction in blood pressure," Martin says.
Martin believes differences in the nutrients in breast milk and formula may explain why breast-feeding lowers blood pressure.
Breast-fed children consume less salt, which can influence blood pressure. And breast milk also contains long-chain polyunsaturated fatty acids, which affect tissue development in the body, including blood vessels, he says.
Moreover, formula feeding can lead to overfeeding and overweight babies. Excess weight is associated with higher blood pressure and insulin resistance, which often leads to diabetes in adulthood, Martin says.
While the researcher found only a small difference in blood pressure between breast-fed and bottle-fed babies, this difference may increase over time, something other studies have suggested, he says.
If this difference does increase over time, this finding becomes significant, because blood pressure is associated with heart disease in later life, Martin says.
Martin says that the team will continue to follow these children and measure their blood pressure as they grow into adulthood.
Mothers who breast-feed know some of its benefits, such as fewer infections and greater bonding with their child, but these findings extend the benefits into adulthood, Martin says.
"Even if this benefit is small, it is added to all the other benefits of breast-feeding, so breast-feeding is probably the best way to start your child off in life," he adds.
Wight says that most British women don't breast-feed for very long, so they may not see the full effect of breast-feeding on blood pressure.
"If women breast-fed the way they should, which is exclusive breast-feeding for six months followed by breast-feeding with the addition of normal food for at least one to two years, we might see bigger reductions in blood pressure," she says.
Wight recommends that "we stay with what nature intended and developed for us over the last couple of hundred thousand years."
"We are seeing more and more research that suggests that breast-feeding is not only the best thing for your baby, but can have long-term health advantages," she says.