But it is possible all babies could benefit in a similar way, say experts.

A team from the Institute of Child Health at Great Ormond Street Hospital, London, carried out a study to test the hypothesis that early diet influences blood pressure in later life.

Blood pressure among the breast-fed babies was on average lower than those fed on formula.

Writing in The Lancet medical journal, the investigators conclude that breast milk consumption in children born prematurely was associated with lower blood pressure in later life.

However, they say that more work needs to be done before it can be established that breast milk has a similar effect on full term babies.

Previous studies have shown that a decrease of three points on the blood pressure scale among the population could result in a 17% reduction in high blood pressure rates, a 15% drop in the risk of stroke and a 6% fall in the risk of coronary heart disease.

Reasons

Report author Professor Alan Lucas said: "Our findings are consistent with the hypothesis that high blood pressure in later life, at last partly, has early nutritional origins, and provide supportive evidence for a potential long-term beneficial effect of breast feeding.

"It is looking quite possible that all babies fed on breast milk may end up with lower blood pressure in later life, and if this is so then that has a major implication for public health and the drive to reduce strokes and coronary heart disease."

The reasons why consumption of formula milk is more likely to increase blood pressure are not known.

Some experts have suggested that it is linked to levels of sodium and fat in the milk.

However, the researchers have discounted this theory as they found no difference in the blood pressure of the babies fed preterm and standard formula, despite the fact that there were substantial differences in the fat and sodium contents of the two milks.

A second theory is that only human milk can stimulate structural or metabolic changes in the body that affect blood pressure.

Professor Lucas told BBC News Online that breast milk contained a wide range of nutrients not found in formula milk. These include: immune factors, human cells, hormones, growth factors and enzymes.

Another theory is that children's subsequent dietary preferences are determined by the type of milk they are first given as babies, and that those who are fed formula opt for less healthy foods later on.

In an accompanying editorial, Susan Roberts, from the US Department of Agriculture Human Nutrition Research Center, said further studies were needed to assess whether giving babies formula milk increased their risk of heart disease.

She said many studies had shown people with high blood pressure were more likely to die prematurely.

But she added: "Blood pressure is only one of the factors influencing cardiovascular disease (CVD), and information is needed on the long-term effect of formula on other known risk factors, such as blood lipids and body fatness."

"Nevertheless, the weight of current evidence indicates adverse effects of formula milk on CVD risk factors, which is consistent with the observations of increased mortality among older adults who were fed formula as infants."