The Big Question: Where do the latest findings leave the debate on breast-feeding?

Why are we asking this now?

Just when you thought scientists had made their minds up on a topic – from life on Mars to the health dangers of bacon butties – another study comes along to upset the consensus. This week researchers reported that breastfeeding babies boosted their IQs by seven points. However, this only occurs in those babies who have inherited a particular gene called FADS2, they found. Fortunately nine out of 10 children have the necessary gene. For the one in 10 who don't, breast feeding makes no difference to intelligence. Bottle feeding, in this regard, is equally good.

Is this the last word on the subject?

Unlikely. The link between breast feeding and intelligence has been debated since 1929 when the first paper on the subject was published. We thought we had heard the last word a year ago when the largest scientific study of the supposed link concluded that breast-fed babies were indeed smarter – but not because of the milk they were fed.

Instead the researchers, from the University of Edinburgh, said they were smarter because their mothers were. Women who breast-fed tended to be more intelligent and more highly educated, and provided more stimulation for their babies at home. The higher IQ of their babies was mostly inherited, accounting for 75 per cent of the difference. The rest of the difference was due to their environment – breast-fed babies had mothers who were older, better educated and lived in nicer homes where they received more attention.

Terrie and Abshalom Moffit, the husband and wife team who published this week's study based on 3,000 children in the UK and New Zealand, said they had corrected for these factors – and they still found a seven-point IQ difference.

Is a higher IQ the main benefit?

No. There are many others, from improving bonding between mother and baby immediately after birth to boosting the baby's immune system through delivery of colustrum, the first antibody. This is the rich, thick yellowish milk produced in small quantities before the mature milk comes in. Breast-feeding is thought to protect against infections and allergies, reducing the risk of asthma and eczema in childhood. It also reduces the risk of diabetes, high blood pressure and obesity in adulthood. Other advantages: It is convenient. It delivers the right balance of nutrients, at the right temperature and best of all it is convenient, quick and costs nothing, unlike formula milk. It even protects the mother – mothers who breast-feed have a lower risk of breast cancer.

Do all women breast-feed?

No. The number has been growing over the last decade but it is not regarded as high enough. In England and Wales 77 per cent of babies are breast-fed (2005 figures) but this falls to 55 per cent within a week, and more than a third of mothers stop within the first six weeks.

British rates of breast-feeding are the lowest in Europe. It is class-related – nine out of 10 mothers in the professional and managerial class start breast feeding, compared with just over six out of 10 among manual workers. By six months, just one in five babies are receiving any breast milk, although the World Health Organisation says babies need nothing other than breast milk for the first six months.

Are the pressures to breast-feed growing?

There is a certain amount of political correctness among the proponents of breast-feeding that brooks no opposition. The result is women who can't or won't breast-feed end up feeling guilty. Parenting websites are full of tales of women upset by unsympathetic friends, nurses or doctors when they failed to meet this test of motherhood.

One is quoted as saying: "I was never able to breast-feed Charlie as my milk was making him sick and we were told by the doctors to stop breast-feeding. He was in intensive care and was tube-fed for the first eight weeks. Then I was told yesterday by a doctor that the reason why Charlie gets sick now is that he wasn't breast-fed and it is my fault."

What puts women off breast-feeding?

All sorts of reasons, from discomfort to difficulty producing sufficient milk to fears about physical appearance. A common reason cited is that the baby rejected the breast. Breast-feeding is a skill that needs to be learned. and often these difficulties can be overcome with a little help and support at the start. The principal reasons why women stop breast-feeding early (within six weeks) are that they have insufficient milk, the process is too long or too tiring, or they have returned to work. The support of friends and relatives is crucial to whether women continue. Nine out of 10 women who stopped breast-feeding within six weeks say they would have liked to continue for longer.

How many women bottle-feed their babies?

Less than a third start bottle feeding but the numbers rise rapidly. By the tenth week nearly six out of 10 babies are fed on formula milk. In addition, some breast-feeding mothers top up their feeds with a bottle – 45 per cent are doing so by the time the baby is five months old. In total, three quarters of babies receive formula milk as part of their diet.

Formula milk is bad for babies, isn't it?

It depends where you live. For most of us in the West, formula milk is a perfectly adequate substitute for breast milk where the real thing is not available. In the developing world it is different.

Where access to clean water with which to mix the powdered formula is a problem, bottle feeding can be a killer because it exposes the baby to bacteria causing diarrhoea and other diseases. That is why breast has been promoted in the developing world as best and the formula milk manufacturers have been accused of overselling their products with heavy marketing campaigns which have undermined this vital message.

Hasn't Aids complicated the issue?

Yes. HIV can be passed from mother to baby via breast milk which has given formula milk a new advantage. But among the poorest women, who are least likely to have access to clean water, the risks of disease from the water used to mix the formula milk still outrank the risks of HIV from breast milk. Even in the era of Aids, breast is still best for these women and their babies – but it is an unhappy choice that they are forced to make.

Is there too much pressure on women to breast-feed?

Yes...

* Some women have been made to feel guilty through their inability to breast-feed

* It is difficult to give a six-month-old enough calories with breast milk alone

* In the developing world, breast-feeding may be dangerous in women with HIV

No...

* More than 20 per cent of women never attempt to breast-feed their babies at all

* Nine out of 10 who stop breast-feeding in the first six weeks do so before they want to

* Breast milk is best for boosting the baby's health and resistance to infection