Where does breast milk come from?

Today’s daf (Nidda 9a) says the following:

תניא נמי הכי  דם נעכר ונעשה חלב דברי ר"מ  רבי יוסי אומר  אבריה מתפרקין ואין נפשה חוזרת עליה עד עשרים וארבע חדש  א"ר אלעאי  מאי טעמא דר"מ דכתיב  (איוב יד, ד) מי יתן טהור מטמא לא אחד

The Gemara has a dispute why a nursing woman doesn’t get her period. Rabbi Meir says that the blood turns into milk and therefore there are no periods because there is no blood. How does Rabbi Meir know this? He learns it out from a pasuk that tahor milk comes from tameh blood.

We see here that not only did Rabbi Meir get the science wrong but he got the Torah wrong. Since we know that blood doesn’t turn into milk Rabbi Meir’s derasha of the pasuk is also wrong.