The new findings shed light into the link of dietary salt and asthma incidence – a so far controversial discussed topic – and offers options to define dietary recommendations for the prevention of asthma or during its therapy.

Combined Epidemiological and Mechanistic Studies

Epidemiological research was conducted using the UK Biobank Resource. Data were obtained from 42,976 participants with a history of allergies. Salt intake was measured objectively by 24-hour sodium excretion estimated from spot urine, and subjectively by self-reported frequency of salt added to food, and its association with asthma incidence was assessed by Cox regression, adjusting for relevant covariates. For mechanistic studies, a mouse model of mite-induced allergic airway inflammation (AAI) fed with high-salt diet (HSD) or normal-salt chow was used to characterize disease development. The microbiome of lung and feces (as proxy for gut) was analyzed via 16S rRNA gene based metabarcoding approach. The investigations demonstrated that in humans, urinary sodium excretion and reported frequency of added salt were both directly associated with asthma incidence among females but not among males. HSD-fed female mice displayed an aggravated AAI characterized by increased levels of total IgE, a T_H2-T_H17-biased inflammatory cell infiltration accompanied by upregulation of osmosensitive stress genes. HSD induced distinct changes in serum short chain fatty acids and in both gut and lung microbiome, with a lower Bacteroidetes to Firmicutes ratio and decreased Lactobacillus relative abundance in the gut, and enriched members of Gammaproteobacteria in the lung. The authors conclude that high dietary salt consumption correlates with asthma incidence in female adults with a history of allergies and the mechanism involves HSD-induced T cell lung inflammatory profiles accompanied by alterations of gut and lung microbiome.

Association Between High Intake of Dietary Salt and Asthma Incidence in Females

This publication combines outcomes from a very large, population-based prospective cohort study of adults to evaluate associations of dietary salt intake with allergic asthma incidence with results obtained using a mouse allergy model aimed at investigating underlying mechanisms of the high salt diet-induced disease exacerbation. The epidemiological study discovers novel associations between high intake of dietary salt and asthma incidence in females but not in males. Mechanistic data in female mice confirm the HSD-induced aggravation of allergic outcomes, characterized by induction of specific inflammatory T cell profiles and reduction of regulatory T cells, which are both of key immunological interest. Furthermore, high salt consumption induces alterations of short chain fatty acids in serum and of gut and lung microbiome.

Changes in Gut Microbiota

Overall, the current study shows novel mechanisms that are triggered by high salt diet in lung allergic inflammation. Furthermore, changes in gut microbiota could be used to identify individuals who might benefit from salt intake reduction for the prevention of asthma or during its therapy.

Original Publication
S. Musiol et al.: 2024: The impact of high-salt diet on asthma in humans and mice: Effect on specific T-cell signatures and microbiome. Allergy, 2024;00:1–14. https://doi.org/10.1111/all.16148