Better nutrition linked to better asthma control Eating a healthy diet with plenty of vegetables, fruits, and whole grains was associated with fewer asthma symptoms and greater asthma control in a large, cross-sectional study involving French adults. Close to 35,000 adults participated in the study, and roughly a quarter of the participants had documented asthma. Eating a healthy diet was associated with a 30% lower chance of experiencing asthma symptoms among men and a 20% lower chance among women, compared with eating an unhealthy diet high in red meat, salt, and sugar. Men and women who reported eating healthy diets also had a 60% and 27% lower risk for poorly controlled asthma, respectively, than men and women who ate unhealthy diets. The study, published online in the European Respiratory Journal, is among the first to assess the impact of diet on asthma severity and control, said Roland Andrianasolo of Université Paris 13, and colleagues. "Existing research on the relationship between diet and asthma is inconclusive, and compared to other chronic diseases, the role of diet in asthma is still debated. This has resulted in a lack of clear nutritional recommendations for asthma prevention, and little guidance for people living with asthma on how to reduce their symptoms through diet." For the new study, participants were recruited from the large, web-based prospective NutriNet-Sante study. At baseline and twice a year subsequently, all participants were invited to complete three self-administered, validated, web-based 24-hour dietary-recall questionnaires: the Alternate Healthy Eating Index 2010 (AHEI-2010), the literature-based adherence score to Mediterranean diet (MEDI-LITE), and the modified Programme National Nutrition Sante-Guideline Score (mPNNS-GS). In 2017, a total of 34,766 NutriNet-Sante participants answered a detailed respiratory questionnaire. Asthma was defined by the asthma symptom score, as the sum of five questions, and asthma control was determined by the asthma control test (ACT). Among women and men, 28% and 25%, respectively, reported having at least one asthma symptom over the previous 12 months. The analysis revealed: Among both women and men, after adjustment for age, a healthier diet as measured by AHEI-2010 was negatively and significantly associated with the asthma symptom score; after adjustments for potential confounders, the association remained statistically significant When healthy diet was assessed by the MEDI-LITE diet score, similar associations were reported among women and men When healthy diet was assessed by mPNNS-GS, a negative and significant association between greater adherence to the mPNNS-GS and lower asthma symptoms was reported; however, the strength of the association decreased among women Of the 40,152 women and men who responded to the respiratory survey, 3,116 reported ever having asthma and 2,609 completed the ACT questionnaire. Asthma was not controlled (ACT≤19) in 15% of women and 11% of men. Among both women and men, those with uncontrolled asthma were significantly younger. For the MEDI-LITE diet score, the researchers reported a negative significant association with uncontrolled asthma in women and a not-quite-significant association in men (P=0.10). When healthy diet was assessed by the mPNNS-GS score, negative associations were also reported between a greater adherence to the diet score and uncontrolled asthma, but this was significant only in men. For AHEI-2010 and MEDI-LITE, the E-value was 2.08 in women. In men, E-values were 4.56 for AHEI-2010, 3.10 for MEDI-LITE, and 5.91 for mPNNS-GS. (E-value represents the minimum strength of association that an unmeasured confounder would need to have with both the exposure and the outcome to fully explain the association.) "Roughly 25% of participants reported at least one asthma symptom, and for the three dietary scores, we observed a statistically significant negative association between a healthier diet and the asthma symptom score (for AHEI-2010, the adjusted OR was 0.79, 95% CI 0.75 to 0.84, for women and 0.67, 95% CI 0.60 to 0.75, for men)," the researchers wrote. "Among participants with asthma (n=2609) we also observed a negative association between a healthier diet and poorly controlled asthma. This was significant in men (OR 0.39, 95% CI 0.18 to 0.84, for the AHEI-2010) and borderline significant in women (OR 0.73, 95% CI 0.53 to 1.01, for the AHEI-2010; P=0.06 for trend)." Study strengths cited by the researchers included the large sample size and the use of multiple dietary quality measures. Study limitations included the cross-sectional design and the self-reported dietary data. "Regarding potential mechanisms, it has been extensively reported that a better quality diet (high in fruits, vegetables and legumes) is associated with lower inflammatory biomarkers," the team continued. "However, besides the well-known anti-oxidant and anti-inflammatory hypotheses in the diet–asthma association, a recent hypothesis has been raised involving an imbalance in gut microbiota -- in particular through a reduction in short-chain fatty acids (SCFAs)." Andrianasolo and colleagues explained that higher levels of SCFAs, produced by bacteria in the gut during fermentation of insoluble fiber from dietary plant matter, were recently associated with a healthy diet (defined in that research as a high intake of fruit, vegetables, and legumes -- i.e., high-fiber foods) and were also reported to reduce airway inflammation. "In this manner, dietary intervention based on a fiber-rich diet might be relevant for both primary and secondary prevention of asthma." Source
