Board Thread:Theories and Speculation/@comment-3568954-20141031085827/@comment-10330822-20141031091627

You forget though that Shizune explained that Tsunade's Creation Rebirth abuses her body significantly, it causes her cells to reach her hayflick limit much faster than normal. In short, her body is even older than she should be for her age. This was also a concern with Naruto's rapid healing, because Jiraiya mentioned that it was literally shortening his life span.