Table 2.

Summary of studies of nutrients and the lung microbiota in bronchiectasis.

References	Type of study	Point of focus	Main findings
Niksarlioglu et al. (40)	Case-Control	Vitamin D	Vitamin D deficiency was common in patients with bronchiectasis and associated with significantly lower forced vital capacity.
Fagihi et al. (41)	Case Study	Vitamin D	Co-infection of SARS-CoV-2 and Bordetella bronchiseptica in a bronchiectasis case was treated with vitamin D supplementation (100,000 IU bolus dose and weekly dose of 25,000 IU), doxycycline and standard intensive care.
Woo et al. (42)	Observational	Lung microbiota	The lung microbiota of patients with non-cystic fibrosis bronchiectasis was relatively stable.
Bartley et al. (43)	Pilot Intervention Study	Vitamin D	Adults with bronchiectasis had higher than expected serum vitamin D levels and standard oral vitamin D3 supplementation further increased this and health-related quality of life measures.
Byun et al. (44)	Cross-sectional	Lung microbiota	Lung microbiota was no different between stable and exacerbated bronchiectasis.
Mirra et al. (45)	Pilot Cross-sectional study	Vitamin D	79% of patients with bronchiectasis had vitamin D deficiency-to-insufficiency; hypovitaminosis D was common.
Chalmers et al. (46)	Observational Study	Vitamin D	Vitamin-D deficiency was common in bronchiectasis and correlated with bacterial colonisation, inflammatory mediator levels in sputum and reductions in lung function.
Javadmoosavi et al. (47)	Cross-sectional study	Zinc	Serum zinc levels were lower in patients with bronchiectasis compared with controls.
Tunney et al. (48)	Cross-sectional	Lung microbiota	After treatment of patients with bronchiectasis for exacerbations (flare ups) no changes in lung microbiota composition were observed.