I always assumed that most of the health benefits came from things like increased social interaction, and the simple fact that if you have a heart attack or stroke or a fall, someone's there to dial 911.
I imagine that for the social aspect of it, it's only a win/lose if one person gets more stress than joy out of the relationship.
I think that's the standard interpretation (i.e., human interaction is the lifesaver). However, when you start to drill down on the whole (gut) bacteria thing, I think things change. Sure, emotions also have impact on the immune system, but so do bacteria. Love IS a powerful emotion. As bacteria are as well ;) The irony (?) is gut bacteria have also been linked to mental conditions / emotions.
I love you...because your gut told my gut to say that? :)
I imagine that for the social aspect of it, it's only a win/lose if one person gets more stress than joy out of the relationship.