A longtime vegetarian, Gualberto also followed a macrobiotic diet. He maintained a strict lifestyle that entailed drinking no alcoholic beverages or coffee, meditation, exercise and yoga. In a television interview, interviewer Mario Pintor asked Gualberto Castro what he did to keep his singing voice intact after so many years of performances. Gualberto answered: "It is not magic to keep one's voice, but with discipline. If you are a person who stays out late at night, drinks alcohol, smokes cigarettes, and carouses around, well, your singing voice will change tone, perhaps get graveled, and finally, you can't sing. I use the paradigm of Tito Guízar: he was 90 years old and he was still singing in the same key as when he was young. At 90 years old he still could sing opera because he was a disciplined person. The same with Don Pedro Vargas, both of them died singing."