Consuming more than 14 or more cured meat products per month was associated with a 93 per cent increase in chronic obstructive pulmonary disease (COPD), report the authors in the American Journal of Respiratory and Critical Care Medicine. The nitrite content of cured meat has been proposed to be behind the observations.
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.
An independent expert has said the implications of the research may be on our understanding on what causes COPD beyond cigarette smoke.
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.
The researchers, from Columbia University Medical Center in New York, used data from the third National Health and Nutritional Examination Survey (NHANES) on 7,352 subjects (52 per cent female) over the age of 45, 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 consumption of cured meat at least once every two days on average (at least 14 times a month) was associated with a 91 per cent increase in developing COPD.
"Cured meats, such as bacon, sausage, luncheon meats and cured hams, are high in nitrites, which are added to meat products as a preservative, an anti-microbial agent, and a colour fixative," said lead author Rui Jiang. "Nitrates generate reactive nitrogen species that may cause damage to the lungs, producing structural changes resembling emphysema."
Jiang added that male smokers of a lower socioeconomic status were more likely to frequently consume cured meats, compared to other demographic groups.
"Those who consumed cured meats more frequently had lower intakes of vitamin C, beta-carotene, fish, fruits, vegetables, and vitamin or mineral supplements. They also had higher intakes of vitamin E and total energy," he said.
The researchers cautioned, however, that the results need to be backed up by significant further research before any recommendations could be made.
"Frequent cured meat consumption was associated independently with an obstructive pattern of lung function and increased odds of COPD. Additional studies are required to determine if cured meat consumption is a causal risk factor for COPD," they concluded.
Commenting independently on the research, Professor Peter Calverly of the British Thoracic Society told the BBC: "This study illustrates that factors other than smoking may contribute to COPD.
"Although smoking remains the single most significant cause of COPD this research seems to suggest other factors may result in increased risk of the disease."
Source: American Journal of Respiratory and Critical Care Medicine
15 April 2007, Volume 175, Pages 798-804
"Cured meat consumption, lung function, and chronic obstructive pulmonary disease among United States adult"
Authors: R. Jiang, D.C. Paik, J.L. Hankinson, R.G. Barr