Lettuce juice may be better for your oral health than mouthwash, say scientists.
Leafy greens contain lots of nitrate, which can reduce bacteria and acidity in the mouth that cause gum disease and tooth decay.
It comes after a disputed study linked alcohol-based mouthwash to cancer this week.
Researchers in Belgium claimed that Listerine Cool Mint raised levels of two bacteria in the mouth that may cause oesophageal and colorectal tumours.
Looking for alternatives to the morning swish, Mia Burleigh and Siobhan Moran, of the University of West Scotland, studied the effect of nitrate on oral health in athletes.
Consuming lettuce juice for two weeks was found to reduce gum inflammation and increased healthy bacteria levels in patients with gum disease
They found that drinking beetroot juice, which contains high levels of nitrate, protected their teeth from acidic sports drinks and carbohydrate gels during exercise.
The told The Conversation: ‘Our work has shown that treating plaque samples from periodontal disease patients with nitrate increased healthy bacteria levels and reduced acidity.
‘For example, consuming lettuce juice for two weeks reduced gum inflammation and increased healthy bacteria levels in patients with gum disease.
‘Growing evidence suggests that nitrate is a cornerstone of oral health. Crunching on a portion of vegetables at mealtimes can help to prevent or treat oral disease and keeps the mouth fresh and healthy.’
They said the two main types of gum disease are gingivitis and periodontitis.
Gingivitis causes redness, swelling and bleeding of the gums. Periodontitis causes damage to the soft tissues and bones supporting the teeth.
As well as tooth loss, it may contribute to the development of cardiovascular disease, dementia, diabetes and rheumatoid arthritis.
Inadequate brushing and flossing leads to the build-up of plaque, a sticky layer of bacteria, on teeth and gums. This causes tooth decay and gum disease.
Leafy greens like spinach, lettuce and beetroots are rich in vitamins, minerals, antioxidants and nitrates.
Nitrates can be turned into nitric oxide by bacteria inside the mouth. This helps to prevent the overgrowth of bad bacteria and reduce oral acidity.
Strong antiseptic mouthwashes are sometimes used to treat gum disease, but these can remove both good and bad bacteria.
Dr Burleigh and PhD candidate Ms Moran said a generous helping of spinach, kale or beetroot, or a daily glass of lettuce juice, offers immediate health benefits without negative side effects.
Meanwhile, researchers at the Institute of Tropical Medicine in Antwerp, Belgium, claimed Listerine Cool Mint mouthwash could increase the amount of Fusobacterium nucleatum and Streptococcus anginosus bacteria in the mouth. Both have been linked to cancer.
In a statement Kenvue, which owns the Listerine brand, dismissed the study and insisted its products are safe.
A spokesman said: ‘Studies on the impact of Listerine on oral health have been published in hundreds of peer-reviewed publications for more than a century, making it one of the most extensively tested oral mouthwash brands in the world.
‘We continuously evaluate the latest science. There is no evidence that Listerine causes cancer.’
