I was really reactive to lots of foods for a long while. I think I had Intestinal dysbiosis (still do a bit). I was reacting to lots of supplements and herbs. I went initially to a naturopath thinking a natural way might help and they gave me herbal concoctions but my stomach just couldn't handle it. I would get nauseous and cramps even on their simplest concoctions.
I was diagnosed with GAD and IBS, but nothing ever seems to help.
I then went on a strict elimination diet (RPAH) for about 6 months (with the help of a trained dietician) as that how long it took my stomach to settle, even on the elimination trials I kept on reacting to foods. On the diet, you could only have listed supplements and medications (which was quite low). For example, there were only a few pandol brands you could have and you had to take off the outer shell. I was only meant to have one Vit D brand, but I cheated.On the diet I slipped up thinking it was okay to have Vit D in liquid form, but turns out the orange oil it was in I was reacting to at the time and made me nauseous. I only had it once and that all it took. I am sure if I tried it now, I would be able to handle it much better.
So eventually my stomach seem to settle down (just the time I think and eating lots of vegetables and lentils) slowly made a difference. I now seem to tolerate supplements much better. At my worst, just one wrong panadol would send me spiralling.
So yes until your stomach settles, do not add anything new that you know affects your stomach. If you can work with a dietician versed in elimination diets and food sensitivities.
For the last 4-6 months, I have been able to bring back much diverse range of foods.
Also, I was getting reoccurring gastritis before all this. I suspect it was because of an underlying food intolerance. I think that's why I kept on getting nauseous and stomach issues as the food items were aggravating my stomach and bringing on gastritis. I think I am intolerant to lactose and probably lots of preservatives. I haven't had nausea and reflux for a long while now on this more tailored diet and removing these things. I think this also helps me introduce more foods. I am hoping it stays that way. But I have had remission periods before and then it flares up again, but I think I have it more under control this time around, and know what is happening.