My Son Is 27 And Is A Smoker. Several Times

My son is 27 and is a smoker. Several times in the past few months, he eats dinner but then becomes very sick, vomiting and becoming very dizzy. Nobody else gets sick from the food so I don't think it's food poisoning He works hard, sleeps about 5 hours a night, and probably doesn't eat the best. Should I be worried about how often this is happening? Do you think there may be more to this or am I overreacting?