A team under epidemiologist fellow Renata Mischa looked at 20 studies from 10 countries with over 1.2 million participants.
What they found was as little as two slices of bacon a day could raise patients' risk of heart disease by 42%, and raise diabetes risk by 19%.
The report in Circulation controlled for lifestyle, and found that the fat contents in both unprocessed and processed meat is roughly the same.
The authors said salt and nitrate preservatives are the most likely cause of the difference.
One solution offered by Englishman Tim Heyward is that you make your own bacon. That may control the nitrates, but you can't make bacon without a whole boatload of salt. When I have made country sausage at home, I also know to load it with salt or it will taste awful. (Worse, like offal.)
Sounds tasty, but Dariush Mozaffarian, who worked on the Mischa study, says replacing saturated fats like pork fat with polyunsaturated fats like olive oil can cut heart disease events (heart attack, stroke etc.) 19%. So it may be the type of fat has something to do with it.
The Mischa study also seems to buttress something the U.S. government is proposing to do already, namely lower the amount of salt in processed foods.
Fact is this is not the first study linking processed meat to bad health -- a 2007 study linked it to COPD, a gradual lessening of lung function that strangles its elderly victims more effectively than a greedy relative with a pillow.
But there's another unanswered question. Could it be the smoke? The Harvard report only looked at processed or unprocessed meat (they excluded poultry, so enjoy that smoked turkey sandwich for now).
I've found you can make a nice barbecue pork shoulder with just a spice rub and a half-cup of Liquid Smoke, in the oven low and slow. Is that better or worse for me than Oscar Meyer bacon, which was probably just injected with a brine solution and may not have been smoked at all?
And, just to pile more confusion on you, a University of Alabama-Birmingham study recently showed that a big breakfast of bacon and eggs, with a modest lunch and a small dinner, may be the best diet for everyone.
So is it the salt, is it the type of fat, is it the smoke, or is it when you eat it all that matters?
We don't know, but we're getting closer to the answers as to both why and how that delicious bacon is killing us so softly with its song.