By Maggie Fox
Washington - Breast-fed babies grow up to have lower blood pressure than bottle-fed children, British researchers reported on Monday.
This could mean they will have lower blood pressure as adults, and thus a lower risk of heart disease, the No 1 killer in the industrialised world, the researchers said.
For every three months a child was breast fed, his or her systolic blood pressure reading - the top number - went down 0.2 points, on average. Breast-feeding time did not significantly affect diastolic blood pressure - the lower number.
"Even this small reduction may have important population-health implications," said Richard Martin, a senior lecturer in epidemiology and public health at the University of Bristol in Britain, who led the study.
"A one percent reduction in population systolic blood pressure levels is associated with about a 1.5 percent reduction in all-cause mortality," Martin added, equivalent to a reduction in premature death of about 8 000 deaths per year in the United States and 2 000 deaths per year in the United Kingdom.
Lower blood pressure is directly linked to lower risk of heart attack, stroke, kidney disease and other related illnesses.
Breast-fed babies are also less likely to be overweight, have fewer behavioural problems and may show differences in intelligence, other studies have shown. Therefore, groups such as the American Academy of Pediatrics recommend that all mothers breast-feed their babies for the first year, and two years if possible.
Writing in the journal Circulation, the researchers said the nutritional content of breast milk may be responsible.
Breast-fed children tend to consume less sodium, which is one factor that can influence blood pressure. Breast milk also contains long-chain polyunsaturated fatty acids, which are compounds that can affect the development of blood vessels.
Infant formula supplemented with these fatty acids has been associated with lower blood pressure.
Formula feeding can also cause babies to eat more than they need and can, in some babies, cause too-rapid weight gain.
"Excess weight is also associated with higher blood pressures and promotes insulin resistance, which often precedes development of diabetes in adulthood," the American Heart Association, which publishes Circulation, said in a statement.
"There is some weak evidence that there is a small lowering of blood pressure in adulthood (among children who were breast fed), but the evidence is inconsistent," Martin said.
"No one has investigated in a prospective study whether the association changes with age."
Martin and his colleagues examined 4 763 seven-year-old children in a long-term health study.
The children who were breast fed for any length of time had lower blood pressure than did formula-fed children.
After adjusting for factors such as mother's education, socioeconomic status and birth weight, the researchers still found lower blood pressure in the breast-fed children.
It was 0.8mm Hg lower for systolic pressure and 0.6mm Hg lower on average on the diastolic pressure reading.
The findings held regardless of the child's sex, body mass, or pulse. Family social status, income, number of siblings, whether the mother drank alcohol, the child's health, and the child's ethnicity did not change the association between breast feeding and blood pressure.