The World Health Organisation suggests that adults should eat no more than 50 grams of sugar (12 teaspoons) per day to avoid the risks of obesity and tooth decay.The UN body even advises that limiting ourselves to 25 grams – or 5% of our daily energy intake – would provide “additional health benefits.”.n Portugal that rises to 25%. So Portuguese adults should be consuming 80% less sugar every day if they are to meet the WHO ’s ultimate recommendation of 5% energy intake (25 grams) of sugar per day.