The nitrite content of cured meat has been proposed to be behind the observations. But R. Graham Barr, an assistant professor of Medicine and Epidemiology at Columbia University Medical Center in New York told FoodNavigator.com that the research, the first to look at the effects of nitrite consumption in humans, has no current implications for the cured meat industry.
"This is a first, cross-sectional, observational study. Further research is needed before we make any recommendations regarding public health," he said.
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.
The implications of the research, said Professor Barr, may be on our understanding on what causes chronic obstructive pulmonary disease (COPD) beyond cigarette smoke.
Chronic obstructive pulmonary disease (COPD) mainly affects smokers, and is the number four cause of death worldwide. It is characterised by chronic inflammation in the small airways of the lung and leads to excessive mucus production, excessive fibrous connective tissue development (fibrosis), and degradation of proteins (proteolysis). There is no cure.
Yet a reported 10 per cent of people who die from COPD are said to have never smoked in their lives, a statistic that suggests that other factors beyond smoking may play a role in the development of the disease.
One such factor may be nitrites in cured meat, Barr and his co-worker Rui Jiang told attendees at last weeks European Respiratory Society annual congress in Munich.
The American researchers noted that animal studies have shown that nitrites in food can produce reactive forms of nitrogen that can damage the lungs, causing alterations in lung structure similar to those that characterise emphysema.
Jiang and Barr used data from the third National Health and Nutritional Examination Survey (NHANES) on 7,581 subjects over the age of 44, for which adequate information was available on lung function and dietary habits. The subject group was representative of the US population of that age.
The NHANES data was accumulated using food frequency questionnaires that asked participants to quantify dietary intake, including that of nitrite-rich foods, such as various types of cured meat (bacon, salami, cured ham, meat within ready meals, etc.).
Following adjustment for age, sex, ethnic group and smoking habits, the data show that subjects who consume cured meat at least once in two days on average (at least 14 times a month) have significantly more lung obstruction than those who never eat it at all.
Lung function was measured by the volume of air that could be forcibly blown out in one second, the so-called forced expiratory volume (FEV1). The researchers reported that people who ate cured meat at least once every other day had a FEV1 that was 115 ml lower lower than subjects who never ate cured meats.
"Subjects who frequently eat cured meat were 71 per cent more likely to have lung function results suggestive of COPD compared to those who never ate cured meats," said Barr.
He cautioned, however, that the results need to be backed up by significant further research before any recommendations could be made.
"First, we need to replicate it in other cross-sectional studies, then we need to replicate in longitudinal studies. The animal studies on nitrite intake and emphysema are about 3 decades old, so additional animal and bench research is warranted," Dr. Barr told FoodNavigator.com.
FoodNavigator.com has not seen the full study data, but Barr said that the research has been submitted to a peer-review journal for publication.