hmmm, not exactly sure whats going on, but heres a theory... your blood sugar was low already as it was the morning,
the grapefruit provided SOME immediate carbs, but the oatmeal is broken down very slowly so it didnt start providing carbs until later,
sooooo, it is possible that the ala forced your blood sugar (from the grapefruit) to be really low, and then as the oatmeal was broken down, you started to feel better...
its a shot in the dark theory, but would seem to make sense.