A long-term observational study of 971 French adults published online in the journal Thorax found the proportion of participants whose asthma symptoms worsened between 2003 and 2007 was notably higher among those who ate more cured meat than those who ate less cured meat.
Specifically, the study, which relied on self-reported information about diet, weight and asthma symptoms, found 22% of the participants who ate four or more servings of cured meat per week experienced worsening asthma symptoms compared to 20% of those who ate one to 3.9 servings per week and 14% of those who ate only one serving per week. Too few participants ate no cured meat weekly to use as a statistically sound control group, according to the researchers.
Participants who ate four or more servings of cured meat per week tended to be younger men, who unsurprisingly were more likely to smoke, have a higher total energy intake and have asthma. But when these and other potentially confounding variables, including education level and dietary patterns, were taken into account, the researchers still found participants who ate four or more servings of cured meat per week were 76% more likely to report intensified asthma symptoms over time than those who consumed one serving or less of cured meat per week.
The finding in some ways mirrors that of previous research that indicated a harmful association between cured meat and different measures of lung health in several countries, but it diverged from two large prospective American studies that found consumption of bacon, hot dogs and sausages may increase the risk of newly diagnosed COPD, but not the incidence of asthma.
NAMI says the connection between asthma and cured meat is not causal, and indeed the researchers note that no causal connection can be determined from an observational study.
"These researchers likely are well intentioned, but their purported findings come down to this: some people who enjoy cured meats also get asthma. But blaming one for the other without real, clinical proof is like blaming the rooster’s crowing for the sun coming up. Just because they are associated, doesn’t mean one caused the other. There is plenty of good science to show that favorites such as salami and sausage can be enjoyed as part of a healthy, balanced diet and that nitrite is not only safe, clinical studies (not studies relying on what people think they ate in the past) show it has many health benefits," NAMI CEO and President Barry Carpenter said in a written statement.
Possible mechanisms of action and the role of BMI
The researchers contextualize the different conclusions by noting that in the American studies, body mass index was considered a confounder, but in the current study it is viewed as a mediator. As a mediator, BMI was associated with only 14% of the total effect, “supporting the hypothesis that the cured meat-asthma association is related to other mechanisms,” according to the study.
After taking out of the equation BMI as a possible mechanism of action for causing the intensified asthma symptoms, the researchers suggest several other potential explanations.
“First, cured meats are rich in nitrite, which may lead to nitrosative stress and oxidative stress related to lung damage and asthma,” the researchers suggest. “Second, the positive relation between cured meat might increase the systemic inflammation, which may have an influence on asthma. In addition, the high content of salt and saturated fat in cured meat might also contribute in part to the association with asthma, though existing evidence has been mainly for childhood-onset asthma.”
To further narrow down the cause of the association, researchers ague additional studies are necessary.
NAMI disputes a possible connection between nitrates and worsening asthma. Carpenter explains in his statement that nitrite is a vasodilator and abronchodilator that helps with asthma, pulmonary hypertension, cystic fibrosis and COPD.
Nonetheless,several newcomers to the meat snack category are limiting nitrates to help reduce the potential health risks with which they are associated or perceived to be associated.
Even though NAMI disputes the study's suggestions, the conclusion could be damaging – especially considering this finding is far from cured meat’s first demerit for potentially damaging health impacts.
As noted in the study, the World Health Organization in late 2015 classified cured meat as a carcinogen. Previous studies also draw connections between red and processed meat intake and a heightened risk of cancer, heart disease, stroke, diabetes, lung cancer and other issues.