Background Vitamin D is the one of the most common nutritional deficiencies worldwide, and insufficiency or deficiency can be associated with musculoskeletal and non-skeletal conditions such as cancer, cardiovascular disease and diabetes mellitus. Objective Recent data suggests that Vitamin D is relatively safe and toxicity is rarer than previously indicated. However, international guidelines regarding dosage and target plasma levels are conflicting. Moreover multiple well-designed studies of healthy older adults, unselected in terms of Vitamin D status, have revealed largely negative results (with the possible exception of older patients in care homes/hospitals) in terms of improvement in musculoskeletal and non-skeletal conditions to date. Conclusion On that basis, it is suggested that future trials regarding Vitamin D supplementation should be carried out in high-risk groups. The use of published criteria for evaluating the effect of nutrients and targeting of individuals with Vitamin D insufficiency and deficiency for inclusion in such studies is also proposed. The identification of specific subgroups that will benefit from supplementation and replacement, and the establishment of a scientific basis for such therapy, should be possible with this approach.