Vitamin D is a fat-soluble vitamin that plays several important roles in the body:

1. Calcium Absorption: Vitamin D helps the body absorb calcium, which is essential for maintaining healthy bones and teeth¹².
2. Bone Health: Adequate levels of vitamin D prevent bone diseases such as osteoporosis in adults and rickets in children²³.
3. Muscle Function: It supports muscle function, including muscle movement³.
4. Nerve Function: Vitamin D is critical for transmitting signals between the brain and other body parts³.
5. Immune System: It plays a role in the immune system, helping the body fend off bacteria and viruses³.

Sources of Vitamin D

Vitamin D can be obtained through:

• Sunlight: The body produces vitamin D when the skin is exposed to sunlight, which is why it is often called the "sunshine" vitamin².
• Food: Few foods naturally contain vitamin D. Some sources include fatty fish (such as tuna, salmon, and mackerel), beef liver, cheese, egg yolks, and fortified foods like milk, orange juice, and cereals⁴⁵.
• Supplements: Vitamin D supplements are available in two forms—D2 (ergocalciferol) and D3 (cholecalciferol). Both forms are effective, but D3 might boost vitamin D levels more effectively²⁶.

Recommended Intake

• Adults (19-70 years): 600 IU (15 mcg) daily⁷.
• Adults (>70 years): 800 IU (20 mcg) daily⁸.
• Upper Limit: 4,000 IU (100 mcg) daily for adults⁷.

Deficiency and Toxicity

• Deficiency: Low levels of vitamin D can lead to weakened bones and immune dysfunction³⁶.
• Toxicity: Excessive vitamin D can cause high calcium levels (hypercalcemia), leading to kidney stones, cardiovascular problems, and bone pain⁴.

For individuals not getting enough from natural sources or exposure, supplements may be necessary, but it's advised to consult with a healthcare provider for personalized guidance.

Footnotes

1. Mayo Clinic ↩

2. MedlinePlus ↩ ↩² ↩³ ↩⁴

3. MedlinePlus ↩ ↩² ↩³ ↩⁴ ↩⁵

4. NHS ↩ ↩²

5. Harvard Nutrition Source ↩

6. Medical News Today ↩ ↩²

7. Mayo Clinic ↩ ↩²

8. Office of Dietary Supplements ↩