Does "feel sick" always mean "feel nausea" or can it sometimes mean "have a stomachache"?
ma22) Kids need a certain amount of vitamins and calcium each day to stay healthy. A glass of milk is an excellent source of them. But not all kids can digest milk. Milk makes some kids feel sick, or even throw up.
There's a slight AmE/BrE difference there. In BrE, if I say "I feel sick", it does mean that I feel as if I might vomit. If I have a headache or stomach ache or have the flu etc, I say "I feel ill".
If a child is lactose intolerant, then ingesting milk can have a few different effects - a rash, a runny nose, feeling nauseous and/or throwing up. In the context of the passage though, I would read "some kids feel sick" to mean "some kids feel as if they are going to vomit". Some them actually do vomit.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.
As 5jj always said, context does seem to matter. In this context, it seems "feeling as if you're going to vomit". I was translating like that to a person in front of me, but he stopped me, saying "It means "being sick"", Suddenly, I hesitated contradicting him, thinking he might be right.
But I'll tell him as emsr said, and also in other contexts in America, it could mean "generally being sick."
"Feeling sick" could mean any type of cold or flu symptom. But in context here, talking about ingesting milk, it would mean that their stomachs or digestive system did not agree with the milk.