Any food we eat goes straight through our mouths, but the effect that diet has on oral health is much wider than that.
Factors in our blood signal a systemic response to the foods we eat, which might, in a roundabout way, influence the health of our gums and teeth.
Researchers looking for ways to treat serious gum disease (periodontitis) are now taking that wider view, exploring dietary approaches that affect the body as a whole, not just the mouth.
Their latest focus, in new research published in the Journal of Clinical Periodontology, is the fast-mimicking diet (FMD), which puts tight restrictions on calorie intake for several days.
The link is inflammation, where the body's immune system reacts too intensely for too long. Diets like the FMD can reduce inflammation in the body, and periodontitis is an inflammatory disease.
So, might this be one way to treat gum disease?
To investigate, an international team of researchers recruited 28 periodontitis patients: Half were put on a restrictive diet for five days, and half were told to continue their eating and drinking normally.
After six months, those following the FMD had fewer markers of inflammation in their blood and gingival crevicular fluid – the liquid that sits between the teeth and the gums.
For both the mouth and the body as a whole, inflammation signals were reduced in the FMD group.
"Our study suggests lifestyle modifications could be important alongside proper tooth brushing for patients," says periodontologist Giuseppe Mainas, from King's College London.
Those on the FMD were asked to consume just 1,100 calories for two days, then 750 calories for the next three days. On days six and seven, their prescribed diets went back to normal.
This weekly pattern was repeated three times over three months, with follow-up and blood tests lasting another three months.
For comparison, men generally need 2,500 calories per day to stay healthy, while for women the figure is 2,000 calories. A banana would give you around 100 calories.
It's worth noting that both groups also went through a deep cleaning routine for their periodontitis at the start of the six-month study period. The calorie restriction was a complementary treatment, not the only one.
This deep cleaning, a standard treatment for advanced gum disease, actually causes inflammation spikes in the mouth – that's one of the reasons the researchers wanted to see if dieting could help.
It's also important to clarify that in terms of their periodontitis clearing up, both groups were about the same. Ultimately, the FMD didn't affect how quickly or substantially the gum disease disappeared, but it did lower signs of inflammation.
That should mean a more positive outlook in terms of long-term health – though the researchers didn't test that here – as well as a reduced risk of the inflammation caused by gum disease having knock-on effects.
Periodontitis has previously been linked to higher risks of strokes and brain damage, so the problems it can lead to don't seem to be limited to the mouth.
The researchers suggest there may be multiple reasons why fasting is beneficial to gum disease patients.
"Fasting reduces oxidative stress in the body, a common cause of inflammation, which can damage cells and DNA," explains periodontologist Luigi Nibali, from King's College London.
"Intake of high calorific foods and refined carbohydrates, for example in cakes and biscuits, can also cause inflammation – so restricting these foods also reduces oxidative stress in the body."
These findings match up with previous studies that have connected healthy dieting with lower levels of inflammation in the body, and with a reduced risk of gum disease.
While the researchers are keen to run longer studies involving more people, the signs are that following particular diets alongside standard deep cleaning could be beneficial for people with periodontitis.
It might also be possible to find ways to produce the same anti-inflammatory effects in people who can't restrict their calories for whatever reason (such as diabetics).
Related: Silencing Bacterial 'Chatter' in Your Mouth May Help Prevent Tooth Decay
"The tested intervention resulted in changes in local and systemic inflammatory responses; however, these findings should be interpreted as exploratory," the researchers write in their published paper.
"Exploratory biomarker trends indicate that further investigation in a fully powered trial is warranted, although no clinical efficacy conclusions can be drawn at this stage."
The research has been published in the Journal of Clinical Periodontology.
This article was fact-checked by Rachel Garner and edited by Clare Watson. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.