Breast not always best for babies, says study
Published 07/01/2010 | 05:00
Women should forget what they have been told about the health benefits of breastfeeding, it was claimed yesterday.
A controversial new study has concluded that, contrary to the view of many experts, breast is not necessarily best for children in the first months of life.
Professor Sven Carlsen, who led the Norwegian team, declared: "Baby formula is as good as breast milk."
What really affects the health of a growing infant is the hormone balance in the womb before birth, he said.
This in turn influences a woman's ability to breast feed, resulting in a misleading association between breastfeeding and child health, it is claimed.
The only benefit from breastfeeding supported by evidence is a "small IQ advantage", said the scientists. And even this is yet to be properly confirmed.
Prof Carlsen's team reviewed over 50 international studies of the relationship between breastfeeding and health.
Most concluded that the more children were breastfed, the healthier they were.
On the surface this was correct, said Prof Carlsen, from the Norwegian University of Science and Technology in Trondheim. But he added: "Even if this is statistically true, it is not because of breastfeeding itself. There are very few studies that have examined the underlying controls on breastfeeding ability."
The largest study on breastfeeding was conducted in Belarus and involved more than 17,000 women and children who were monitored for six years.
It "cut the legs out from underneath most of the assertions that breastfeeding has health benefits", said the scientists.
For example, the study found no evidence that breastfeeding reduced the risk of asthma and allergies in children.
Mental ability was the only area where a small benefit was seen by the experts.
"It appears that children who are breastfed have a small IQ advantage," said Prof Carlsen. "But this needs to be confirmed in new, carefully planned and conducted studies."
The Norwegian scientists' own work pointed to links between levels of androgen male hormones in the wombs of pregnant women, the health of children, and breastfeeding.
"Pregnant women who have higher levels of androgens breastfeed less," said Prof Carlsen. "Probably this is a direct effect of hormones that simply limit nursing ability by reducing milk production in the breast."
A pregnant woman's health affected hormones in her womb, which had knock-on effects on her unborn child, said the researchers.
Normally a certain amount of the androgen testosterone is converted to the female hormone oestrogen in the placenta, the vital organ that supplies oxygen and nutrients to the foetus and links mother and child.
This is an energy-intensive process, said Prof Carlsen. If the placenta is underpowered, some of the testosterone that should be converted remains unchanged and impacts the unborn baby and its mother.
For the mother, this leads to reduced development of glandular tissue in the breasts so her ability to make milk is impaired.
Adverse effects on the child can include an increased risk of obesity, type 2 diabetes, and polycystic ovary syndrome in girls.