In the world of Dragon Ball, massive battles and martial-arts tournaments are the way of life. This means overcoming massive injuries when a fight has been exceedingly difficult. Luckily, the Z-Warriors and their allies have access to the restorative powers of the Senzu Beans. Any fight where the going gets tough, the heroes of Dragon Ball get going thanks in part to their stash of Senzu Beans, which sometimes even helps them get stronger.
Senzu Beans are one of the most enduring things from Dragon Ball, consistently appearing throughout the franchise — they're never stopped being useful. However, as helpful as they are, Korin's superfood has also almost doomed the world on occasion.
The Senzu Beans were introduced in the original Dragon Ball series, during the Commander Red Saga. They're grown by the ancient martial arts master Korin in his tower and apparently taste a bit like fish, with the consistency of celery. The beans are so filling that eating just one can sufficiently feed a grown man for 10 days. However, eating too many at once can lead to massive weight gain, like when Yajirobe ate a handful at once and put on weight almost instantly.
The Senzu Beans are capable of magically restoring the health and stamina of anyone who ingests one. The healing effect is almost instantaneous, strengthening anyone who consumes them and healing any major wounds. This even extends to otherwise fatal injuries, such as when Yamcha was impaled through the chest by Doctor Gero during the Android Saga in Dragon Ball Z. The blow would have likely been a mortal wound on the human warrior, but he was given a Senzu Bean in time, allowing him to quickly heal from the attack. These instant healing effects even come with an added benefit for Saiyans. Thanks to their natural ability to become stronger after healing from any near-fatal injury, the Senzu Beans don't just heal the Saiyans, but also enhances their power level.
The Beans aren't perfect -- they only work on recent injuries, with older losses of limb unable to be restored by them. This is confirmed by Future Trunks, whose mentor Gohan lost an arm to Android 17 and Android 18. Despite eventually eating Senzu Beans, Gohan's arm wasn't restored -- but Future Trunks believes that it would have worked if he'd eaten the bean quickly enough after the injury. After befriending Korin, Goku and his allies gained regular access to the beans, which quickly became a major element of the Z-Warriors strategy going forward. Especially when the heroes were forced into lengthy campaigns that required them to quickly heal and adapt to threats from across the galaxy.
Without the Senzu Beans, the heroes would have likely been unable to heal and grow to keep up with the scores of powerful enemies the Z-Warriors encountered over the years. Notably, the Senzu Beans don't only work on the heroes, but on anyone who eats them -- including villains. At various points in the franchise, Goku's competitive and fight-obsessed attitude led him to give Senzu Beans to enemies like Perfect Cell in Dragon Ball Z and Moro in Dragon Ball Super. This resulted in the winded and wounded villains being capable of keeping up the fight against Goku and his allies, with the entire world being put at risk because Goku wanted a fair fight. The Senzu Beans are still one of the most reliable tools the heroes of Dragon Ball have, even decades into the franchise.
