Research over the past decade has reinforced the importance of Vitamin D in human nutrition. In the process, new roles in health maintenance related to immunity and chemoprevention have been added to the nutrients widely known benefits for skeletal health, and, indirectly, for tissue integrity. Vitamin D has now been shown to have a role in protecting against osteoporosis, while supporting brain and immune function.
Out of the new research has come a reevaluation of ideal maximum daily intakes of Vitamin D. A consensus has evolved among researchers that the old RDI of 400 i.u. per day is inadequate. Instead, they point to ideal intakes of vitamin D3 ranging from 1,000 i.u. for infants, up through 2,000 i.u. for children and teenagers. Intake for adults is officially recommended at 2,000 i.u., although as we age, it becomes more difficult to absorb sufficient vitamin D. Therefore, some of the most respected researchers (e.g. Heaney, et. al.) insist that 4,000 to 10,000 i.u. are suitable for older adults in order to maintain immunity and skeletal health.*