The 4- to 6-month guideline has been adopted for more than 25 years in individual countries1 somewhat before the adoption of this arbitrary range by WHO and the North American countries. It was also mentioned in documents intended for Europe as a whole eg, from the European Union and professional societies.2,3

Nevertheless, many mothers ignore these guidelines. For example, in Britain 90% of them have introduced other foods apart from breast milk or formula by the age of 4 months, indeed a quarter of them have done so by the age of 8 weeks.4 Because cows' milk is rarely consumed at this early age embarrassment of renal concentrating ability and hypernatremia are almost never seen now despite this introduction of complementary foods earlier than recommended.

Are these infants coming to any other harm? Alternatively, should we accept that their mothers' instincts to complement earlier are acceptable? One...

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