Throughout comic book history, superheroes (that are not absurdly overpowered for no logical reason) are known to have weaknesses.

Superman is weak against Kryptonite.
Green Lantern can't manage any object that's colored yellow.
Batman is a human being who can still be injured and/or killed.
Catherine Sonora and many other Galos like her have an insatiable appetite for any food that's loaded with citrus, pineapple being Catherine's absolute favorite.

Common Earth food often have varying reactions when consumed by the people of Galohan though for the most part, most Earth food are consumable. However, none of Earth's finest cuisines can hold a broken match to Galohan's love for food rich in citrus. The demand for citrus is so great that planets were terraformed specifically for the purpose of producing citrus fruits. You would think that this would surely over-saturate the market and make citrus fruits near worthless given the scale. But on the contrary, this scale is actually relatively light given the huge population in the far off future.

As you would expect though, citrus fruit does have an affect on Galos. Eating too much citrus can acid cook the Galo from the inside out! Yes, this can actually happen to humans as well. Anyways, Galos get around this by diluting citrus fruits by mixing in other kinds of food.

Catherine Sonora belongs to me.
Art by  toughset