According to Catholicism, would it be wrong for a husband to intentionally eat in such a way as to decrease fertility?

Contraception is not OK according to the Catholic Church, with the exception of fertility awareness methods (FAMs), which involve abstinence when a woman is in the part of her cycle where she is fertile. However, there are ways to decrease male fertility, such as getting 'snipped' (a vasectomy), which the Catholic Church says constitutes a mortal sin. A Catholic.com article states > "A vasectomy constitutes grave matter. Together with full knowledge of > the gravity of the action and full and free consent to the action, a > mortal sin is committed." What about simply eating in a way that is intended to decrease male fertility, such as going vegan and eating lots of soy, say - according to the Catholic Church, would that also be sinful, and if so, would it constitute a mortal sin or would it be a venial sin?