Thanks for reading. Yes, there are differences between the two approaches. It’s very hard to find published data on the exact amount of FODMAPs in reported “high FODMAP foods”. I only find lists of foods “high in FODMAPs”. If I had the exact amounts of FODMAPs in each food, I could look at adjusting the FP for those foods if required. But you would still need to consider that FODMAPs are reportedly reflected in the dietary fiber measurement by US carbohydrate test methods and therefore should be included in the final FP. Recall fiber is added directly in calculating FP.
At any rate, it won’t make that much difference in foods that contain relatively small amounts of total carbohydrate. Foods that have few carbs including onions, garlic, broccoli, cabbage, asparagus, mushrooms, avocado and sprouts will have relatively low FPs regardless of the exact amount of FODMAPs. Therefore, these foods should not be big drivers of symptoms when consumed in moderation – for instance adding some diced onion or a couple garlic cloves to your stir fry. Of course, if you find that any of these foods cause you problems, I support you in avoiding them.