Bacteria in the mouth convert nitrates, also found in vegetables, into nitrites, and this transforms into nitric oxide in the stomach, which stimulates the protective mechanisms of the mucous membrane, according to a research from Uppsala University's Department of Medical Cell Biology.
Nitrites are added to meat to retard rancidity, stabilise flavour, and establish the characteristic pink colour of cured meat. Studies and recommendations by health and governmental organisations ensure the safety of such products.
However, observational studies, including data from the third National Health and Nutritional Examination Survey (NHANES) on 7,352 subjects over the age of 45, have suggested that increased consumption of nitrites from cured meat could increase the risk of lung disease.
"Nitrates in food have long been erroneously linked to an increased risk of cancer," said Joel Petersson. The research forms the basis of Petersson's PhD thesis.
Moreover, studies have shown that vegetables have up to 100 times more nitrate than processed meats, meaning nitrite and nitrate from processed or cured meats may account for only a small quantity of these compounds consumed in the diet.
The Petersson's research offers some positive news for the additives. He used animal models to show that nitrate additives in food protect against both gastric ulcers and the minor damage that often occurs in the gastrointestinal (GI) tract when people consume anti-inflammatory drugs.
"These sorts of drugs are very common in the event of pain and inflammation. They have the major disadvantage of causing a large number of serious side effects in the form of bleeding and ulcers in the gastrointestinal tract. With the aid of a nitrate-rich diet you can thus avoid such damage," he explained.
Suck it and see
According to the research, the key to the protection lies in the mouth. Bacteria in the oral cavity convert the nitrates to nitrites, which are then swallowed. To study this, Petersson and co-workers fed rats a nitrate-rich feed, while some of the animals also simultaneously received an antibacterial oral spray. Administration of anti-inflammatory drugs led to damage of the mucous membrane only in the animals receiving the oral spray.
"This shows how important our oral flora is," said Petersson. "The fact that these bacteria are not just involved in our oral hygiene but also play an important role in the normal functions of the gastrointestinal tract is not entirely new. It is currently an important issue, as antibacterial mouthwashes have become more and more common. If a mouthwash eliminates the bacterial flora in the mouth this may be important to the normal functioning of the stomach, as the protective levels of nitric oxide greatly decrease."
While the role of oral bacteria has been reported before, Petersson claims that the fact that nitric oxide can also be formed in the stomach from nitrites in the saliva, entirely without the involvement of enzymes, is relatively new.
A effect of nitric oxide on the protective mechanisms of the mucous membrane, including renewal of the mucous layer that covers the mucous membrane and its maintenance of a stable blood flow in the mucous membrane, are reportedly achieved by the effect of nitric oxide, a vasodilator, on widening the blood vessels in the mucous membrane. This increased the blood flow and regulates the elimination of the important mucus.
Results from a mice study, published last year in the prestigious Proceedings of the National Academy of Sciences, reported that nitrites and nitrates may help heart attack survival and recovery.
Researchers from the University of Texas Health Science Center at Houston reported that the compounds reduced heart cell death in the mice following a heart attack by 48 per cent. Moreover, animals with a low nitrite/nitrate diet had 59 per cent greater injury, report the researchers.
Nitrite salts (also known as sodium nitrite) have traditionally been used to cure cooked meat products and fine paste sausages. However labelling of these salts as E250 is now negatively perceived by consumers, meaning that a clean label (non-E-number) alterative could be welcomed by industry and consumers.
Source: J. Petersson (2008)
"Nitrate, Nitrite and Nitric Oxide in Gastric Mucosal Defense"