That's not really how food/biology works. In this case the leghemoglobin is a protein that will be destroyed during digestion, come nowhere near the bloodstrea

That's not really how food/biology works. In this case the leghemoglobin is a protein that will be destroyed during digestion, come nowhere near the bloodstream, and is a protein not a small molecule (there can't be alternative chirality involved in a protein produced in a eukaryote). As the protein is eaten it's broken down into the same small molecules and amino acids as every other protein eaten. Don't inject it into your bloodstream, and don't eat 100% by mass any individual thing and you'll be fine. Such a protein is likely less dissimilar biochemically to eating meat then eating an 'exotic' vegetarian dish.