Hypovitaminosis D in the elderly: from bone to brain.

There is a growing consensus that vitamin D recommended daily intakes for the elderly are far too low, and that all individuals should take as much vitamin D as needed to raise levels to between 32 to 40 ng/ml (80 to 100 nmol/L) (5, 108, 109). Supplementation will likely be necessary in most elderly, since according to current lifestyles, diet and sunlight alone are inadequate sources of vitamin D (17). We believe that to raise and maintain 25(OH) vitamin D levels at a minimum of 32 ng/ml (80 nmol/L), most elderly will require at least 2,000 IU of cholecalciferol per day. But many questions remain. Are other biological markers preferable to 25(OH) vitamin D to assess repletion? Do the current estimates of optimal serum levels provide health benefits for all conditions, or do optimal vitamin D levels differ depending on the target tissue? How much vitamin D, cholecalciferol, or ergocalciferol, should be given to maintain these levels? What are the molecular mechanisms by which vitamin D influences health and disease? Cross-sectional studies have suggested that low vitamin D levels not only predict nursing home admission but also are associated with increased mortality (1, 2). Further knowledge of the mechanisms of vitamin D action and prospective clinical trials designed to determine if supplementation resulting in vitamin D levels higher than those shown to reduce the risk of falls and fractures is also effective in reducing the burden of various medical conditions could help validate a cost-effective intervention that will provide greater quality of life and longevity and have a major public health impact.