Meat, milk, butter and cheese are all avoided by vegans. Putting children on strict vegan diets is “unethical” and could harm their development, a US scientist has argued. Lindsay Allen, of the US Agricultural Research Service, attacked parents who insisted their children lived by the maxim “meat is murder”. Animal source foods have some nutrients not found anywhere else, she told a Washington science conference. The Vegan Society dismissed the claims, saying its research showed vegans were often healthier than meat eaters.