Vitamin D and Immunomodulation: Is It Time to Change the Reference Values?

Area of Science:

• Endocrinology
• Immunology
• Nutritional Science

Background:

• Vitamin D encompasses vitamins D2 and D3, with active vitamin D3 functioning as a neurohormone.
• Beyond calcium-phosphorus metabolism, vitamin D plays significant roles in immunomodulation.
• Vitamin D influences T-helper cell proliferation and cytokine production (both pro- and anti-inflammatory).

Purpose of the Study:

• To highlight the urgent need for redefining vitamin D reference values.
• To address the limitations of current reference values based on parathyroid hormone (PTH) response.
• To advocate for a comprehensive review considering diverse populations.

Main Methods:

• Review of existing literature on vitamin D's biological activities.
• Analysis of vitamin D level distributions in healthy and patient cohorts.
• Evaluation of current methodologies for establishing vitamin D reference ranges.

Main Results:

• Current vitamin D reference values, often based on PTH levels, are considered obsolete due to incomplete understanding of vitamin D biology.
• Vitamin D exhibits pleiotropic effects, including significant immunomodulatory functions.
• Discrepancies exist in vitamin D status across different ethnic, cultural, and geographical groups.

Conclusions:

• A critical re-evaluation of vitamin D reference values is necessary.
• Standardization and harmonization of cut-off values are required.
• Future reference values must incorporate ethnic, cultural, and geographical factors for accurate assessment.