But keep in mind (and I've said this in other threads) that you have to know your audience. If you get into the "whys" of no juice, do you think she's open to hearing it (i.e. actually interested)? Or is she just going to see it as an opening to say "Well I did it with my son, your husband, and he's fine." If they're not interested in the "whys", they just see it as a reason to continue arguing with you. As if you're explaining it because you're still on the fence.
So 'know your audience'. And if they aren't open to what you're saying, the answer is a simple "NO." and walk away.