Roman Catechism 18.158

Chapter 18 — Part II: The Sacraments — The Holy Eucharist

Section 158. Besides, there are many who cannot at all bear the taste or even the smell of wine. Lest, therefore, what is intended for the spiritual health should prove hurtful to the health of the body, it has been most prudently provided by the Church that it should be administered to the people under the species of bread only.