no, really, I can't

I think we all have one of those friends: really nice people whom we wish were not SO friendly. A few weeks back, they heard I was sick and cooked for us. Except neither Gumby nor I can eat their cooking (waaay too salty). And they loaded us up; it wasn't just a single meal. I tried to eat it, but got a tummy ache. This isn't the first time. And probably won't be the last. Yes, I feel bad about throwing out food, but what am I to do? It would help if they'd just make the offer and give us the option to decline.