Taking PreP and fiber supplements together

Hoping one of you medically enlightened GayBros could help me out:

So the only medication I take is Truvada (mornings) and fiber supplements (mornings and evenings). I never thought twice about taking them together in the mornings, but the guy that I'm seeing mentioned that the fiber supplements can decrease the absorbency of the Truvada.

Is there truth to this? I really don't want to have to keep my fiber supplements in my car and take them at work, but I'd much rather have my PreP work!