more than one message digest per signed message?

[Thomas Kuehne]

Is it possible to use more than one message digest when signing a
message with GnuPG?

gpg --digest MD5 --digest SHA512 --clearsign test.txt
-> used digest SHA512

gpg --digest MD5,SHA512 --clearsign test.txt
-> gpg: selected digest algorithm is invalid

gpg --digest "MD5 SHA512" --clearsign test.txt
-> gpg: selected digest algorithm is invalid

Thomas