What caused Wolverine’s reduced healing power?

It was a combination of 1 and 2 and also a 3rd thing: his adamantium skeleton was poisoning him. That one of the interesting things about this film and the character in it; he is basically getting bombarded with things taking a toll on his body the entire time.

I don't think the food supply killed the mutants (maybe earlier versions of it did); I think it did weaken their powers and help with preventing the genes from passing down. Otherwise we would have to accept that it was Charles that killed nearly every mutant; and I doubt that is the case.

I think with X23 and her friend, they were building up an immunity to the food supply or; since they were in captivity, they may been given something to counteract the effects.

I think it's mostly number 2, or entirely that. Part of the film is about aging and getting tried, so Wolverine's powers slowing down are symbolic of this. His claws don't work so good either. He's getting too old for this sh*t. Accepting this and learning to have hope in the face of despair is also a big message of the movie.

Well in the early 1980s X-Men comic Days of Future Past, he was an old man in the future they depicted. So it isn't that far off the basis of the comics for him to be grow old. Though I see where the TC is coming from since some comics have him getting the skin blown off his face with a shotgun and he heals up within a minute. And that he is over 130 years old.

The poisoned food weakened Wolverine's healing ability so his body could no longer be prevented from rejecting his adamantium skeleton.

It's been about a year or so since I saw the movie, but I thought the movie implied the adamantium was basically causing his healing power to constantly be working. Like a constant wound. And after years of regenerating, the ability simply ran out.

It was the adamantium slowly leaching into his body, like other heavy metals often do. Lead. Uranium. It has the same type of toxicity. The damage that was doing was progressing at a slightly faster pace than his body could heal, hence the slow decline. Normally he wouldn't age. I don't think they know how long a mutant like him could live. Possibly indefinitely, only dying when something else killed him and not because his body failed on its own. Like a vampire or one of the Highlander immortals.

They mentioned that something was being put into corn syrup (a common food ingredient) which suppressed the birth of new mutants. As most of them get old and die like the rest of us, this would mean an aging and dwindling population over time. Only mutants that were under agency control and indoctrination would be born after that.

If they actually wanted a shot at mutant kids people could plan their diets around not ingesting any of the additive, I suppose, but they'd have to know it existed and what foods contained it. And that doesn't appear to be public knowledge. Consuming the additive won't harm living mutants or even reduce their powers. It just blocks the so-called mutant X gene in a human fetus.

Your topic makes me think of a stupid retcon they did in comics in recent years. Originally, Wolverine was born in the 1880s when they first did his origin about 23 years ago. But in recent comics they changed it so that now he's born in the 1700s. Which pretty well makes it so his healing factor is now far more powerful than it ever was supposed to be.

Thanks for once again retconning things to be like the movies, Marvel. It's not like we enjoy the differences between comics and movies. No. Just make both the same because you think if the people who only watch the movies, decide to pick up a comic that they'll quit reading if it's not exactly like the movie! Grrrr!