People breastfed as infants have a 24 per cent better chance than their formula-fed counterparts of climbing the social ladder, a study said on Tuesday.

Conversely, being fed mother's milk as a baby also reduced one's chances of social demotion later in life by as much as 20 per cent, said the findings published in the journal Archives Of Disease In Childhood.

The British research team wrote: "Our study adds to evidence on the health benefits of breastfeeding by showing that there may be lifelong social benefits."

The researchers looked at data on 17,419 people born in Britain in 1958 and another 16,771 born in 1970 - comparing their social class at the age of 10 or 11 to that aged 33 or 34, and whether or not they had been breastfed.

Social class was categorised on a four-point scale ranging from unskilled or semi-skilled to professional or managerial.

In the 1958 group, 68 per cent had been breastfed compared with only 36 per cent in the 1970 group, said the study, which claims to be the largest yet to probe the relationship between breastfeeding and social mobility.

The researchers gathered data during regular follow-ups every few years and took into account a range of other potential factors, such as brain development and emotional stress levels.

The researchers said in a statement: "Intellect and stress accounted for around a third (36 per cent) of the total impact of breastfeeding.

"Breastfeeding enhances brain development, which boosts intellect, which in turn increases upward social mobility. Breastfed children also showed fewer signs of stress."

The authors said breast milk contained so-called long-chain polyunsaturated fatty acids or LCPUFAs, which are essential for brain development.

Previous studies, however, have suggested that LCPUFAs alone may not improve cognitive growth. The team said it was impossible to tell which was more beneficial to the child: the nutrients found in breast milk, the skin-on-skin contact and bonding between a nursing mother and her infant, or perhaps a combination of the two.

Further research was needed, they said, to determine whether mothers who fed their infants formula milk could aid their long-term development by mimicking the skin contact between breastfeeding women and their offspring.

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