Senzu bean is known as "magical healing bean", it can heal and restore consumer's health instantly when eaten. Does it cures diseases as well? Such as Goku's heart disease.
If Senzu bean could cure diseases, Goku wouldn't have died in the future and Trunks wouldn't have needed to go back from the future to give him the antidote.
From Dragon ball wikia
However, it appears that the beans can not heal injuries that have already healed over (like Tien's and Yamcha's respective scars or Saiyan tails) or cure ailments (like Goku's heart virus contracted during the Androids Saga)
While there's little concrete evidence, it's likely that Senzu Bean's only heal the type of wounds your body could heal on its own, in Dragonball it was noted that Senzu bean's were very filling, not quite like medicine. So it could be more like they're a "super food" that accelerates the body's natural processes rather than something like conventional medicine.