Chronically malnourished children struggle to read and write simple sentences regardless of their level of schooling, according to research by Save the Children.
Eight-year-olds who are stunted by malnutrition are 19% more likely to make a mistake while reading a simple sentence, the report Food for Thought said.
Stunted children are 12.5% more likely to make a mistake writing a simple sentence and do 7% worse on basic maths questions.
The findings, based on research with thousands of children in Ethiopia, India, Peru and Vietnam, come 10 days before a global nutrition summit in London and ahead of this year's G8.
More top news
The pre-trial hearing for a British banker, accused of murdering two women in Hong Kong last November, was adjourned for five weeks.
Conservationists say one of the UK's most threatened butterflies has recorded its best year for a decade following 2014's warm spring.
The SNP leader Nicola Sturgeon says tonight's TV election debate shows there is a clear demand for a new style of politics across the UK.