Some Catholics capitalize Christ’s Body and Blood. Others lowercase body and blood. Also, some Catholics capitalize divine pronouns, while others lower case them. But all Catholics capitalize Mass.
Second Exodus, following the most respected authorities, the Scriptures and the Catechism, lowercases body and blood and divine pronouns, but always capitalizes Mass.
Body and Blood
The Scriptures
St. Jerome’s Latin Vulgate did not capitalize “This is my body” at Mt 26:26, Mk 14:22, Lk 22:19, and 1 Cor 11:24. The Latin for “my body” is corpus meum. Nor did it capitalize “body and blood” at 1 Cor 11:27. The Latin for “body and blood” is corporis et sanguinis.
The Douay-Rheims translation of St. Jerome’s Latin Vulgate Bible also does not capitalize “This is my body,” at Mt 26:26, Mk 14:22, Lk 22:19, and 1 Cor 11:24. Nor does it capitalize “body and blood” at 1 Cor 11:27.
The Revised Standard Version Catholic Edition does not capitalize “This is my body,” at Mt 26:26, Mk 14:22, Lk 22:19, and 1 Cor 11:24. Nor does it capitalize “body and blood” at 1 Cor 11:27.
The Authorized King James Version does not capitalize “This is my body,” at Mt 26:26, Mk 14:22, Lk 22:19, and 1 Cor 11:24. Nor does it capitalize “body and blood” at 1 Cor 11:27.
The Catechism
The Catechism in the matter of Rabbi Yeshua’s body and blood is inconsistent. We find “body and blood” lowercased in § 948, 1105, 1244, 1350, 1357, 1374, 1382, 1385, 1408, 1524, 2618, and capitalized in § 1275, 1323, 1331, 1333, 1397, 1426, 2042, 2177.
In each case where the Catechism uses, “This is my body,” § 610, 621, 1339, 1365, 1375, 1412, it is lowercased.
Divine Pronouns
The Scriptures
Hebrew has never had capital letters, so the Ancient Jewish Scriptures texts have no teaching for us on this question. The original Greek texts of Sacred Scripture had capital letters but never capitalize pronouns related to God. St. Jerome did not capitalize divine pronouns related to God when he translated the original Greek manuscripts to produce his Latin Vulgate Jn 3:16. The Douay-Rheims (DRA) did not capitalize divine pronouns Jn 3:16. The Revised Standard Version Catholic Edition did not capitalize pronouns Jn 3:16. Neither did the Authorized King James Version Jn 3:16. I checked all the scholarly Scripture translations in my collection. None capitalized pronouns related to God.
The Catechism
The Catechism is the Catholic Church speaking in her own voice. I resolved to follow its usage. So I looked, and saw:
§ 1 God, infinitely perfect and blessed in himself, in a plan of sheer goodness freely created man to make him share in his own blessed life. For this reason, at every time and in every place, God draws close to man. He calls man to seek him, to know him, to love him with all his strength. He calls together all men, scattered and divided by sin, into the unity of his family, the Church. To accomplish this, when the fullness of time had come, God sent his Son as Redeemer and Savior. In his Son and through him, he invites men to become, in the Holy Spirit, his adopted children and thus heirs of his blessed life.
Holy Sacrifice of the Mass
The Mass, the source and summit § 2031 of our Catholic life, is always capitalized. See the Catechism § 1088, 1297, 1330, 1367, 1373, 1382, 1388, 1566, 1621, 1651, 1683, 2042, 2180, 2192.
However, non-liturgical usages such as § 1863 “a number of light objects makes a great mass,” or § 2496 “mass media,” which do not refer to the source and summit, are always lowercased.