Beetroot juice has earned attention for its possible blood pressure and exercise benefits, but the body does not use its nitrate directly. First, bacteria in the mouth help convert nitrate from foods such as beetroot, spinach and kale into nitrite, a compound involved in widening blood vessels and supporting blood flow.
A new study from King’s College London suggests that what happens in the mouth after eating nitrate-rich foods may affect that process. In a short-term study published in the British Journal of Clinical Pharmacology, healthy volunteers who chewed sugar-containing gum after drinking beetroot juice produced more nitrite and had a small drop in blood pressure compared with when they chewed sugar-free gum.
The finding is not a reason to start chewing sugary gum for heart health. The researchers said the effect lasted only several hours, and that regular use of sugar-containing products would not be recommended because of dental health concerns. The study is better understood as a proof of concept: changing conditions in the mouth may influence how the body processes dietary nitrate.
Nitrate is found naturally in some vegetables, especially beetroot and leafy greens. Once nitrate is converted to nitrite, it can contribute to the production of nitric oxide, which helps blood vessels relax. That process is one reason nitrate-rich foods and beetroot juice have been studied for blood pressure and athletic performance.
“Whether and how the acidity of the saliva in the mouth impacts the conversion of the inactive nitrate, to the more active nitrite, is a fundamental question, as it impacts a range of important physiological functions including blood pressure,” said Andrew Webb, PhD, clinical senior lecturer in the School of Cardiovascular & Metabolic Medicine & Sciences at King’s College London. “However, this process has not been studied much.”
To test the idea, researchers randomly assigned healthy volunteers to chew either sugar-containing Hubba Bubba bubble gum or sugar-free Wrigley’s Extra gum for three to six hours after drinking a shot of beetroot juice. Participants returned at least a week later and repeated the experiment with the other type of gum. Researchers analyzed blood and saliva samples throughout the study and measured blood pressure.
When participants chewed the sugar-containing gum, their saliva became more acidic compared with when they chewed sugar-free gum. They also had 45% higher nitrite levels in the mouth and 25% higher nitrite levels around the body.
Blood pressure changed too, though modestly. Compared with sugar-free gum, sugar-containing gum lowered systolic and diastolic blood pressure by almost 3/2 mmHg. Systolic blood pressure is the top number in a reading, measured when the heart pushes blood out. Diastolic blood pressure is the bottom number, measured when the heart relaxes between beats.
The study was designed to test a biological mechanism over several hours, not to evaluate long-term blood pressure management. It involved healthy volunteers after beetroot juice, not people being treated for hypertension.
“While most research suggests that increasing acidity inhibits the conversion of nitrate, this has never been investigated in the whole body, over several hours,” Webb said.
He said the team had previously found that combining grapefruit juice with beetroot juice decreased saliva acidity and inhibited the conversion of nitrate to nitrite. This study tested the opposite idea: whether increasing saliva acidity could enhance conversion.
The answer appeared to be yes, at least under the conditions of this experiment. But the researchers were clear that sugar itself is not the long-term solution.
“The bacteria that live in our mouths play a critical role in converting nitrate from foods such as beetroot into beneficial compounds that help relax blood vessels and lower blood pressure,” said Charlotte Mills, PhD, of the University of Reading and a co-author of the study. “Our findings suggest that the presence of sugar may create a more favourable environment for this process.”
Mills said the goal is not to encourage regular use of sugary gum.
“We are certainly not suggesting that people should start chewing sugary gum regularly,” she said. “Frequent sugar consumption is harmful for dental health and is also detrimental to cardiometabolic health when consumed in excess. Instead, our findings provide a proof of concept that we may be able to improve how the body processes dietary nitrate, and future research should focus on developing tooth-friendly, metabolically sound approaches that achieve the same effect.”
That distinction matters because the study’s headline-grabbing detail could easily be misread. The useful scientific question is not whether sugary gum belongs in a heart-healthy routine. It is whether researchers can find safer ways to improve nitrate conversion in the mouth.
The findings may also be relevant for sports nutrition. Dietary nitrate is already used by some athletes, often through beetroot juice, because of its potential effects on blood flow and exercise performance. If nitrate conversion can be improved without relying on frequent sugar exposure, it could change how athletes use nitrate-rich foods or supplements.
“Because dietary nitrate is already a recognized sports supplement, there is potential to optimize how athletes use it,” Mills said. “If we can enhance nitrate conversion, we may be able to improve the physiological benefits that athletes obtain from nitrate-rich foods.”
The study also highlights the role of the mouth in nutrition. Oral bacteria are often discussed in terms of cavities, gum disease or bad breath, but they also help process some compounds in food before those compounds reach the rest of the body. That makes the mouth part of the body’s metabolic response to certain foods, not just the place where digestion begins.
For now, the study remains a short-term physiology experiment with a surprising result. It points to a possible path for future research on beetroot, leafy greens, nitrate metabolism and exercise performance, while leaving sugary gum exactly where the researchers put it: useful for testing a mechanism, not as advice.
The research was supported by internal infrastructure funding from King’s College London’s British Heart Foundation Centre, a UK Medical Research Council Clinical Research Training Fellowship and research facilities supported by the National Institute for Health and Care Research. Andrew Webb reported holding shares in HeartBeet Ltd, which receives a royalty from James White Drinks Ltd., the company that makes the beetroot juice used in the study.