For children and adults up to age 50, 200 International Units (IU) is the recommended amount of vitamin D per day. With age, we lose some ability to make the vitamin from sunlight exposure and to turn it into its active form, so the recommendation increases to 400 IU per day for those aged 51-70 years, and to 600 IU for those older than 70. In these latter groups, supplements may be needed to reach recommended intake levels.
However, these recommendations were set to assure adequate intakes of the vitamin primarily for bone health. As we learn more about vitamin D and its multiple health benefits, many experts argue that much higher levels are needed for optimal effects. Some researchers would like to see the recommendation increased up to 2,000 IU per day, especially in older people and other high-risk groups. When the committee meets again to reconsider the dietary recommendation, it will likely be increased.