Vitamin D exerts its principal actions on bone metabolism, so it has important benefits on the skeleton. Serum 25(OH)D is directly related to bone mineral density (BMD), so subjects with lower levels have lower BMD and higher prevalence of osteoporosis and fractures, mainly hip and non-vertebral fractures. But, vitamin D has also many other beneficial effects, and its deficit has been associated with a great variety of diseases, such as asthma, cancer, diabetes, hypertension and other cardiovascular diseases, some inflammatory and autoimmune diseases, infections and some liver diseases. It is also remarkable its direct effect on muscle strength, so patients with vitamin D deficiency have higher risk of falls. Supplementation with vitamin D in patients with low 25(OH)D levels has shown a favourable effect not only on bone and muscle, reducing the risk of fracture, but also on inflammation, cell proliferation or immune system, reducing the risk of other diseases and complications. However, observational studies are needed with larger numbers of patients and well-designed randomized clinical trials, with baseline vitamin D determination and accurate monitoring to establish a cause-effect relationship between vitamin D deficiency and some diseases.
Part of the book: A Critical Evaluation of Vitamin D