Table 2.

Studies on the investigation of the role of vitamin D in combating COPD.

Study Type	Study Design	Parameter Examined	Findings	Ref
Clinical Studies	Multi-center, randomized, double-blind, placebo-controlled intervention trial, age > 40 years, 16,800 IU vitamin D3 (n = 120) v/s placebo (n = 120) weekly and orally.	COPD exacerbation, Total lung capacity, and maximum respiratory mouth pressure.		[72]
	Randomized clinical study with a double-blind placebo control, 88 severe COPD patients, placebo receive 100,000 IU vitamin D monthly for six months.	FEV1, COPD exacerbation.	Improved FEV1, Reduces COPD exacerbation.	[40]
	Controlled, randomized, double-blind trial, 50–58 year patents, 200,000 IU followed by 100,000 IU vitamin D monthly for 1.1 years (n = 226) v/s placebo (n = 216).	FEV1, COPD exacerbation.	Only smokers benefitted from vitamin D supplementation, particularly those with vitamin D insufficiency or COPD.	[73]
	Multi-center, randomized, double-blind, placebo-controlled intervention trial, Vitamin D3 (n = 122) v/s Placebo (n = 118)	COPD exacerbation.	Vitamin D3 supplementation reduced the severity of COPD exacerbations in those with mild to severe COPD.	[74]