It is quite well established that Vitamin D supplementation is effective in resolving deficiency for otherwise healthy, non geriatric children and adults. Howe

It is quite well established that Vitamin D supplementation is effective in resolving deficiency for otherwise healthy, non geriatric children and adults. However, when it comes to other populations you would have to consult the literature or a doctor to determine the efficacy of supplementation. Also, supplementation for non deficient individuals lacks long term evidence supportive of utility. Although many think it holds promise as an agent that reduces all cause mortality.