Cover Image


View/Hide Left Panel

Research Topic

Research Questions and Identified Needs

Sun Exposure

  1. Investigate whether a minimal-risk ultraviolet B (UVB) radiation exposure relative to skin cancer exists that also enables vitamin D production.

  2. Clarify how physiological factors such as skin pigmentation, genetics age, body weight, and body composition influence vitamin D synthesis.

  3. Clarify how environmental factors such as sunscreen use affect vitamin D synthesis.

Step 3: Intake Assessment

Intake Assessment

  1. Enhance dietary assessment methods for calcium and vitamin D intake, and methods for the measurement of calcium and vitamin D in foods and supplements.

  2. Investigate food and supplement sources of calcium and vitamin D for bioequivalence, bioavailability, and safety.

  3. Improve the standardization of assay for serum 25OHD.


The committee found an overall lack of causal evidence from intervention studies for the task of identifying health outcome indicators. This was especially true for non-skeletal outcomes for vitamin D, but this was also true for skeletal outcomes, particularly in certain life stage groups. Data related to calcium were sparse for children and younger adults. Most vitamin D studies were conducted using older persons or postmenopausal women. Some available data suggested the possibility of ethnic differences in bone health, but this suggestion could not be further clarified. Very few studies explored the independent effects of calcium and vitamin D. Only limited data were available on adverse health effects. These information gaps, coupled with challenges in synthesizing disparate evidence for either calcium or vitamin D or their combination, presented challenges to DRI development. Further, lack of clarity concerning the physiology and metabolism of vitamin D was problematic as was the ability to judge the effects of vitamin D as a nutrient given its role as a prohormone.

Research Needs Related to Health Outcomes and Related Conditions

  1. Clarify threshold effects of calcium and vitamin D on skeletal health outcomes by life stage and for different racial/ethnic

The National Academies of Sciences, Engineering, and Medicine
500 Fifth St. N.W. | Washington, D.C. 20001

Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement