Yep. I like grapefruit and grapefruit juice, but one of my medications says to never take it while on the med. When I asked the doc why he said something in grapefruit increases the effect of the med. So naturally I asked could I cut the med dose on days when I had grapefruit. He said there's no way to monitor the individual effect.
That is what my ENDO tells me, no grapefruit, SOY, list of foods is longer though, walnuts, Broccoli family all interfere with Synthyroid. Having Gastropresis a paralyzed colon my diet consist of easy digest foods. Carbs are the easiest to digest but to many pushes you towards Type 2 Diabetes, and those meds are nasty. My oldest takes Metformin and hates it and has severe Neuropathy. Still has to work 50+ hrs a week on his feet.