He set up camp, and felt a little congested and short of breath. He remembered his ancestors used the plants from the land as medicines, and he remembered that Milkwort did something but he couldn't remember what. But since he had an abundance of it nearby he decided he'd go ahead and eat some. He started feeling a little different after a while, and figured that the Milkwort was helping so he ate a little more of it before going to sleep.
The next morning he awoke feeling a lot better, but he couldn't help but notice he also felt different. As he sat up from his sleeping bag, he right away noticed a heavy weight on his chest. He looked down and found that over the coarse of the night he had grown two big breasts. But that wasn't the only thing. He then got up and went to go pee near a tree, and found that his penis was gone. It had been replaced by a vagina.
John couldn't believe what had happened to him, and thought he was still asleep and having some sort of weird dream. So he decided he'd pinch himself on the nipples, but when he did milk shot out. As he felt a wave of sensitivity by touching his new breast, he smiled and thought that things could be worse.
The thing about Milkwort that John couldn't remember which he later found out when he went home was, that there is an ancient belief that nursing mothers could increase lactation by eating the plants of that genus. But since he wasn't a woman, instead eating the plant turned him into one in order to help his body lactate.