truism
noun [ C ] uk/ˈtruː.ɪ.zəm/ us/ˈtruː.ɪ.zəm/
自明之理，不言而喻的话
a statement that is so obviously true that it is almost not worth saying
As far as health is concerned, it's a truism that prevention is better than cure. 就健康而言，预防胜于治疗，这是不言而喻的。