Vitamin D is a fat-soluble vitamin that functions as both a nutrient and a hormone. It is essential for various bodily functions, including the absorption and retention of calcium and phosphorus, which are critical for bone health¹. Here are some key points about Vitamin D:

Benefits

1. Bone Health: Vitamin D helps in the absorption of calcium, which is essential for building and maintaining healthy bones. Deficiency can lead to bone diseases such as osteoporosis and rickets².
2. Immune Function: It plays a role in maintaining a healthy immune system, helping to fight off bacteria and viruses³.
3. Other Health Benefits: Research suggests that adequate levels of vitamin D may lower the risk of conditions like osteoporosis, multiple sclerosis, rheumatoid arthritis, chronic pain, diabetes, high blood pressure, cardiovascular disease, and some cancers⁴.

Sources

1. Sunlight: The body produces Vitamin D when the skin is exposed to sunlight. However, factors such as geographical location, skin pigmentation, and lifestyle can impact the amount of vitamin D produced¹.
2. Food: Very few foods naturally contain vitamin D. These include fatty fish (such as salmon and mackerel), beef liver, cheese, and egg yolks. Some foods are fortified with vitamin D, including milk, orange juice, and cereals³.
3. Supplements: Vitamin D is available as a dietary supplement in two forms: D2 (ergocalciferol) and D3 (cholecalciferol). D3 is generally considered more effective at raising blood levels of vitamin D⁵.

Recommended Dosage

• RDA (Recommended Dietary Allowance): For adults aged 19-70, it is 600 IU (15 mcg) daily; for adults over 70, it is 800 IU (20 mcg) daily⁶.
• UL (Tolerable Upper Intake Level): The maximum daily intake unlikely to cause adverse health effects is 4,000 IU (100 mcg) for adults⁶.

Safety

Vitamin D supplementation is generally safe, even at relatively high doses, but excessive intake can lead to toxicity, causing symptoms such as anorexia, weight loss, polyuria, and heart arrhythmias due to hypercalcemia (high calcium levels in the blood)⁷.

Footnotes

1. Harvard T.H. Chan School of Public Health - Vitamin D ↩ ↩²

2. MedlinePlus - Vitamin D ↩

3. PubMed - Sources of vitamin D for humans ↩ ↩²

4. Better Health Channel - Vitamin D ↩

5. Journal of Steroid Biochemistry and Molecular Biology - Long-term vitamin D3 supplementation ↩

6. Mayo Clinic News Network - How much vitamin D do I need? ↩ ↩²

7. PMC - Vitamin D dosing in long-term hospitalized patients ↩