Does flossing help reduce inflammation in your body?
Cleaning between your teeth every day keeps gum inflammation in check. Interdental brushes do this more effectively than ordinary dental floss.
Poor oral hygiene demonstrably fuels inflammation in the gums. When many studies were combined, covering thirty studies with a total of 594 volunteers, it became clear that as soon as people stopped brushing, plaque levels rose and local proteins linked to inflammation in the fluid around the gums rose along with them. The link between plaque and local gum inflammation is therefore well established.
But does that also mean flossing helps reduce inflammation elsewhere in your body? That has not been shown. Those thirty studies measured inflammation in the gums themselves, not in your blood or other organs. The leap from 'healthier gums' to 'less inflammation throughout the body' is biologically plausible, but has not yet been confirmed in people.
There is also the question of the best way to clean between your teeth. When many studies were combined, the conclusion was that interdental brushes (small brushes you work between the teeth) outperform floss for removing plaque and reducing gum inflammation. Floss still has its place in spots where such a brush would not fit without causing damage, but as a standard daily habit it scores lower.
Finally, a large study following more than 17,000 Americans found that people who flossed five or more times per week were 26.5% less likely to be depressed than non-flossers. That is a striking figure, but the relationship could run the other way, or simply reflect a generally healthier lifestyle. This is not proof that flossing itself prevents depression.
This answer draws on two combined overviews of existing research and one large study following people over time. The link between plaque and local gum inflammation is the most solidly supported finding. Whether flossing also reduces inflammation elsewhere in the body was not directly tested in any of the studies included here. The researchers themselves emphasise that the associations found are local, and that cause-and-effect evidence for broader effects is lacking.