From the Guidelines
The Recommended Dietary Allowance (RDA) for vitamin D is 600 IU/d for adults aged 19 to 70 years and 800 IU/d for adults older than 70 years, as recommended by the Institute of Medicine 1. This recommendation is based on the estimated requirement to meet or exceed the vitamin D needs of 97.5% of the adult population, assuming minimal sun exposure. Some key points to consider:
- The RDA for vitamin D varies by age, with older adults requiring more due to decreased skin synthesis and increased risk of deficiency 1.
- Total serum 25-(OH)D levels of 40 nmol/L (16 ng/mL) meet the needs of approximately half of the population, and levels of 50 nmol/L (20 ng/mL) or greater meet the needs of nearly all of the population 1.
- Other organizations, such as the Endocrine Society, recommend screening for vitamin D deficiency only in persons at risk and define vitamin D deficiency as total serum 25-(OH)D levels of less than 50 nmol/L (<20 ng/mL) 1.
- It is essential to note that excessive intake of fat-soluble vitamins, including vitamin D, can be harmful as they are stored in the body, whereas water-soluble vitamins are generally safer as excess amounts are excreted. Key considerations for vitamin D intake include:
- Age: older adults require more vitamin D due to decreased skin synthesis and increased risk of deficiency 1.
- Sun exposure: minimal sun exposure is assumed in the RDA recommendation, and individuals with limited sun exposure may require more vitamin D 1.
- Dietary sources: vitamin D can be obtained through dietary sources, such as fatty fish, fortified dairy products, and supplements, but many individuals may not get enough from diet alone 1.
From the Research
Recommended Dietary Allowance (RDA) for Vitamin D
- The US Institute of Medicine Recommended Dietary Allowance of vitamin D is 400 IU per day for children younger than 1 year of age, 600 IU per day for children at least 1 year of age and adults up to 70 years, and 800 IU per day for older adults 2.
- The US Endocrine Society's Clinical Practice Guideline suggested that 400-1000 IU per day may be needed for children aged less than 1 year, 600-1000 IU per day for children aged 1 year or more, and 1500-2000 IU per day for adults aged 19 years or more to maintain 25(OH)D above the optimal level of 30 ng/ml 2.
- A dose-response study suggests a mean requirement of at least 500 IU (12.5 microg) from which an RDA could be set for vitamin D 3.
Recommended Dietary Allowance (RDA) for Other Vitamins
- The current recommended dietary allowance (RDA) for vitamin C for adult nonsmoking men and women is 60 mg/d, but recent scientific evidence indicates that an increased intake of vitamin C is associated with a reduced risk of chronic diseases 4.
- The calculated RDA for healthy older women were 2,230 μg retinol equivalents for vitamin A, 2.8 μg for vitamin B-12,0.9 mg for thiamin, 1.4 mg for riboflavin, 3.6 mg for pantothenic acid, 1.4 mg for vitamin B-6,320 μg for folic acid, and 115 mg for vitamin C 5.
- Tolerable upper intake levels have been established by the Food and Nutrition Board, Institute of Medicine, at 1000 mg for vitamin E and 2000 mg for vitamin C in adults 6.