I agree with the one tiny teaspoon bit -- I challenged my son's soy intolerance with an entire pot of soy yogurt, stupid stupid thing to do
He vomited it all up two hours later. Dr has agreed that it was likely the heaviness of so much yogurt in his tummy all at once, especially when it was something he'd never had before.
He then advised me to go with bread - in the UK all commercially produced bread has soy flour (well, I've never found one that doesn't!). But, it is a small amount and isn't straight SOY product. Also, it then opens up a LOT of food options now!
He's been on bread for a week now so in a few days I am going to try the yogurt again. ONE SPOONFUL!