Bit of a "useless use of env" here. You don't need the env program for establishing environment variables for the execution of a command. That is a built-in shell feature:

    VAR1=val1 VAR2=val2 ... command

However, env here is serving the purpose of avoiding unwanted recursion, because "env man" runs the external man rather than the function. But we can get that with the "command" builtin, or by using "/usr/bin/man":

Thus:

  man() {
    LESS_TERMCAP_mb=$(printf "\e[1;31m") \
    LESS_TERMCAP_md=$(printf "\e[1;31m") \
    LESS_TERMCAP_me=$(printf "\e[0m") \
    LESS_TERMCAP_se=$(printf "\e[0m") \
    LESS_TERMCAP_so=$(printf "\e[1;44;33m") \
    LESS_TERMCAP_ue=$(printf "\e[0m") \
    LESS_TERMCAP_us=$(printf "\e[1;32m") \
    command man "$@"
  }