A British study has found no reliable association between breastfeeding and higher IQ at age two.

Breastfeeding does little to improve a child's intelligence, despite the widespread belief that "breast is best" for IQ, research has shown.

Scientists who conducted a study of 11,000 British children found no reliable association between breastfeeding and higher IQ at age two.

Nor was breastfeeding related to improvements in IQ after the age of two, indicating that it did not help young brains develop better over time.

The children were taking part in the Twins Early Development Study (Teds) set up to disentangle the impact of "nature and nurture" on growing children.

Breastfeeding was associated with a small IQ advantage for girls at age two, but by 16 this had disappeared.

"Breastfeeding has little benefit for early life intelligence and cognitive growth from toddlerhood through adolescence," the scientists concluded in online journal Public Library of Science ONE.

Goldsmiths, University of London, study co-leader Dr Sophie von Stumm said few of the earlier studies looking at the link between IQ and breastfeeding have used strong research designs that produce reliable results.

"Children - and adults - differ in their cognitive abilities, and it is important to identify factors that give rise to these differences.

"But comparatively small events like breastfeeding are very unlikely to be at the core of something as big and complex as children's differences in IQ.

"Instead, children's IQ differences are better explained by long-term factors, for example, children's family background and their schooling."

She stressed that breastfeeding had other benefits, such as helping to build a child's immune system, but added that "mothers should be aware that they are not harming their child if they choose not to, or cannot, breastfeed".

"Being bottle fed as an infant won't cost your child a chance at a university degree later in life."