Welcome to Rejuvenation Science®!

 Questions? Please call us at
1-888-737-3588 TOLL FREE

Harvard Researchers Recommend 1000+ IU Vitamin D

For years the recommended (minimum) daily intake of vitamin D was 400 international units (IU). Newer research indicates that this number is significantly too low.

Researchers at the Harvard School of Public Health writing in the July 2006 edition of the American Journal of Clinical Nutrition stated that recent evidence suggests vitamin D intake above current recommendations is associated with better health. The review article summarized evidence from various medical studies regarding concentrations of vitamin D in the blood stream in relation to bone mineral density, dental health, risk of falls, fractures and colorectal cancer.

Researchers stated that the most advantageous vitamin D levels could not be reached with current recommended intake of 200 IU and 600 IU per day for younger and older adults respectively. Scientists indicated that intake for all adults of at least 1,000 IU of vitamin D-3 daily is needed to bring at least 50% of adult blood serum vitamin D concentrations to healthier levels.


Recent evidence suggests that vitamin D intakes above current recommendations may be associated with better health outcomes. However, optimal serum concentrations of 25-hydroxyvitamin D [25(OH)D] have not been defined. This review summarizes evidence from studies that evaluated thresholds for serum 25(OH)D concentrations in relation to bone mineral density (BMD), lower-extremity function, dental health, and risk of falls, fractures, and colorectal cancer.

For all endpoints, the most advantageous serum concentrations of 25(OH)D begin at 75 nmol/L (30 ng/mL), and the best are between 90 and 100 nmol/L (36-40 ng/mL). In most persons, these concentrations could not be reached with the currently recommended intakes of 200 and 600 IU vitamin D/d for younger and older adults, respectively. A comparison of vitamin D intakes with achieved serum concentrations of 25(OH)D for the purpose of estimating optimal intakes led us to suggest that, for bone health in younger adults and all studied outcomes in older adults, an increase in the currently recommended intake of vitamin D is warranted. An intake for all adults of >/=1000 IU (40 mug) vitamin D (cholecalciferol)/d is needed to bring vitamin D concentrations in no less than 50% of the population up to 75 nmol/L. The implications of higher doses for the entire adult population should be addressed in future studies.


Bischoff-Ferrari HA, Giovannucci E, Willett WC, Dietrich T, Dawson-Hughes B. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr 2006 Jul; 84:18-28.

Key concepts: Vitamin D, recommended daily intake