Adding the clinical framing, because it changes how the question reads. The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either. Those three things can all be true at once, and most arguments here are two people holding different parts of that.

HPLC_Greg said:

For anyone reading later: the numbers in this thread are worth checking against a primary source before you act on them, including mine.

Bookmarking. The distinction being drawn above is the one nobody else makes. Sending this to two other people who asked me the same thing last week.

From the other side of the consultation, briefly. It helps to ask what evidence would change your mind before you look at any. If nothing would, the discussion is not about evidence, and it is better to say so early than to spend nine posts discovering it.

Dr.EM_Chicago said:

It helps to ask what evidence would change your mind before you look at any.

Same pattern here, and in the same order. The detail I would add is minor and it is already implied above.

Moderator note: leaving this open. It is being argued well and the disagreement is the useful part.