Giving vitamin D to TB patients who are vitamin D deficient may be beneficial in a proportion of patients. When taken as a group, vitamin D supplementation appears to have no benefit when using sputum culture conversion as an endpoint, and giving vitamin D supplements to TB patients who have normal vitamin D levels does not provide any benefit from the point of view of TB. In a subset of patients with the "tt" genotype of the TaqI vitamin D receptor and who are vitamin D deficient, vitamin D supplementation appears to hasten sputum culture conversion. There are no studies of vitamin D using the gold standard outcome of relapse, so the true benefit of vitamin D is not at present known.