“An expert panel of dentists and cardiologists, writing in the American Heart Association journal Circulation, says there is no evidence that treating or preventing gum disease has any direct effect on heart health.”
https://www.npr.org/sections/health-shots/2012/04/19/150955149/flossing-is-good-for-the-gums-but-doesnt-help-the-heart
Flossing is still very good for you, though. Flossing removes debris from between your teeth and gums that makes food for bacteria. Bacteria growing out of control makes people sick. Poor oral care is a big risk factor for getting pneumonia in populations with weakened immune systems. It has recently been discovered that it is normal for elderly people to aspirate saliva in their sleep. It goes into their lungs and they can get pneumonia. Many elderly people have swallowing disorders and are even more at risk of getting pneumonia from bacteria going from their mouths into their lungs.
I can tell you as a speech-language pathologist who treats patients with swallowing disorders, that flossing as part of a daily comprehensive oral care regimen not only prevents pneumonia and death, but also reduces the incidence of fevers, AND has a more powerful effect on treatment of pneumonia than prescription antibiotics! (Best treatment is both together.)
I also know from personal experience that flossing helps me have a cleaner mouth. I have noticed that I breathe easier and my lungs feel healthier when I floss. I think it would be very good if everyone flossed.
So, I also learned from your question that I need to check my sources before passing along statements I have heard, even from people who are supposed to be more educated on a subject than me.
I really like flossing. Have you ever been to the dentist to get a cavity filled in? It's not very nice! Flossing is the only way to clean food from between your teeth, which will help avoid cavities. My teeth catch a lot of food (TMI) so it's important.
I used to have a water jet which is also very good if your gums are too sensitive for flossing, but it doesn't work as well as flossing.
Floss your teeth, brush your tongue, gargle (just water) and drink lots of water and you'll have great protection from bad breath 🙂