The Romans, as Monty Python famously acknowledged, have done many things for us. Contrary to popular wisdom, however, improving our diet was not one of them.

A study of the remains of almost 20,000 people dating from the 8th century BC to the 18th century AD has found that the Roman empire reduced our level of nutrition, which increased again in the "dark ages".

That is because the key factor in determining average height over the centuries – an indicator of nutritional status and wellbeing – has been an increase in milk consumption due to improved farming. Higher population densities and the need to feed the army during Roman times may have worked against this.