From the Guidelines
The optimal blood level of vitamin D3 is generally considered to be between 30-50 nanograms per milliliter (ng/mL) or 75-125 nanomoles per liter (nmol/L), and to maintain this level, most adults need approximately 600-800 IU (15-20 mcg) of vitamin D3 daily. To determine the specific needs of an individual, a blood test measuring 25-hydroxyvitamin D levels is recommended. If supplementation is needed, vitamin D3 (cholecalciferol) is typically recommended over vitamin D2 as it's more effective at raising blood levels 1. It's essential to take supplements with a meal containing some fat to improve absorption. Vitamin D is crucial for calcium absorption, bone health, immune function, and may play roles in mood regulation and reducing inflammation. Levels below 20 ng/mL indicate deficiency, while levels above 100 ng/mL may cause toxicity with symptoms like nausea, kidney problems, and excessive calcium in the blood. Some key points to consider:
- The Institute of Medicine recommends a daily intake of 600 IU for individuals from 1 to 70 years of age, and 800 IU for individuals 71 and older 1.
- The use of vitamin D supplements may not require daily replacement, as 25(OH)D3 has a half-life of 2 weeks to 3 months and is stored primarily in adipose tissue and the liver 1.
- Summer sun exposure may provide enough vitamin D for the winter, and major institutions have used dosing schedules as infrequent as once every 1–4 months 1. It's essential to consult with a healthcare professional to determine the best course of action for individual vitamin D needs. Some populations may require higher doses, such as those with limited sun exposure, darker skin, or who are older. In these cases, doses may increase to 1,000-2,000 IU of vitamin D3 daily. However, it's crucial to follow the recommended guidelines and consult with a healthcare professional to avoid toxicity and ensure optimal vitamin D levels.
From the Research
Optimal Level of Vitamin D3
The optimal level of vitamin D3 is a topic of ongoing debate, with various studies suggesting different thresholds for optimal serum 25-hydroxyvitamin D (25(OH)D) concentrations.
- The Institute of Medicine suggests that most North Americans receive sufficient vitamin D from their diet and sun exposure, with optimal serum concentrations ranging from 30-80 ng/ml 2.
- Other studies suggest that serum 25(OH)D levels above 20 ng/mL can normalize calcium and bone homeostasis, with a daily intake of 500-700 IU of vitamin D3 sufficient to maintain serum 25OHD levels of 20 ng/mL 3.
- However, some research suggests that higher serum concentrations (> 30 ng/mL) may be associated with reduced risks of major diseases and mortality, including pregnancy and birth outcomes 4, 5.
- The recommended target levels for 25(OH)D range from 25 to 50 nmol/l (10 to 20 ng/ml), corresponding to a vitamin D intake of 400 to 800 International Units (10 to 20 μg) per day 6.
Serum 25-Hydroxyvitamin D Concentrations
The optimal serum 25(OH)D concentrations are as follows:
- Deficiency: < 20 ng/ml 2, 3
- Insufficiency: 20-30 ng/ml 2
- Optimal: 30-80 ng/ml 2, > 30 ng/mL 4, 5
- Desirable for cancer prevention: 36-48 ng/ml 5
Daily Intake of Vitamin D3
The daily intake of vitamin D3 required to achieve optimal serum 25(OH)D concentrations is: