Michelle Starr in CNet:
It's commonly accepted that life expectancy in the Middle Ages was pretty low, hovering around the early 30s — mainly because of the hazards of childhood. If a person made it to adulthood, the average was in the 60s — but, although that's comparable with today's global life expectancy, the world was still a much more dangerous — and openly vicious — place. It wasn't, for example, unusual for popes and kings to be assassinated.
Take Cangrande I della Scala. Born in 1291, he rose to rule Verona in 1311 at the age of 20, and was a skilled warrior and ruler, claiming several additional territories for his family's rule. He was also the most prominent patron of poet Dante Alighieri, and was considered a brave, yet merciful man.
In the year 1328, at the age of 37, he took possession of the Padua region, after 16 years of bloody conflict. In 1329, he prepared to move on Mantua, formerly the seat of a trusted ally with whom he had become estranged, but postponed the action due to a change of government at Treviso, a territory long contested and the last slice of the Veneto region to fall into his control.
But his triumphal procession into Treviso was spoiled by a sudden, sharp illness. Rumour had it that Cangrande had become ill after drinking from a polluted spring a few days before. The most powerful man in Verona's history reached his lodgings four days after entering Treviso, took to bed and promptly died on 22 July 1329, at the age of 38. Immediately, rumours proliferated that someone had poisoned the nobleman.
Now, a study published in the Journal of Archaeological Science has revealed that the rumoured poisoning was actually the case.