Vitamin D status: measurement, interpretation, and clinical application

Area of Science:

• Endocrinology
• Nutritional Science
• Public Health

Background:

• Vitamin D, often called the sunshine vitamin, is recognized for its role in bone health.
• Emerging research highlights its potential benefits in reducing the risk of chronic diseases like autoimmune conditions, cancer, and cardiovascular disease.
• Vitamin D undergoes two hydroxylations to become biologically active: 25-hydroxyvitamin D [25(OH)D] in the liver and 1,25-dihydroxyvitamin D [1,25(OH)(2)D] in the kidney.

Purpose of the Study:

• To emphasize the importance of vitamin D beyond bone health.
• To clarify the role of vitamin D metabolites in assessing vitamin D status.
• To establish target serum levels for vitamin D sufficiency.

Main Methods:

• Measurement of serum 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)(2)D] levels.
• Clinical assessment of vitamin D status based on serum 25(OH)D concentrations.
• Review of expert consensus on vitamin D deficiency and insufficiency thresholds.

Main Results:

• Serum 25(OH)D is the established indicator of vitamin D status.
• Serum 1,25(OH)(2)D levels do not accurately reflect vitamin D status and can be misleading.
• Vitamin D deficiency is defined as 25(OH)D <20 ng/mL, and insufficiency as 21-29 ng/mL.

Conclusions:

• Maintaining serum 25(OH)D levels above 30 ng/mL is recommended for both children and adults.
• Achieving optimal vitamin D levels ensures the full spectrum of health benefits, including reduced chronic disease risk.
• Accurate assessment of vitamin D status relies on measuring serum 25(OH)D, not 1,25(OH)(2)D.