# Vitamin D functions and deficiency information

> Developing situation record from CLSTR: https://clstr.news/situations/vitamin-d-functions-and-deficiency-information
> Updated: 2026-11-01T04:13:40.000Z. Sources: 2. Developments: 2.

Information regarding Vitamin D focuses on its role in calcium and phosphate metabolism, bone health, muscle function, and immune regulation. The nutrient is produced via sunlight exposure and can be obtained through dietary sources such as fatty fish, egg yolks, and fortified products.

Deficiency can lead to serious health issues, including rickets in children and osteomalacia or osteoporosis in adults. High risk groups include the elderly, individuals with limited sun exposure, those with darker skin pigmentation, and people with certain liver, kidney, or gastrointestinal diseases.

Guidelines for optimization suggest that because Vitamin D is fat-soluble, supplements may be more effective when taken with a meal containing fat. Measuring 25-hydroxyvitamin D in the blood is used to determine levels, with different organizations suggesting varying optimal ranges.

## Timeline

### 2026-11-01: Vitamin D: Functions, sources, and supplementation guidelines

Vitamin D is essential for bone and immune health. While sunlight and fatty fish are primary sources, many require supplementation due to dietary or environmental factors.

2 sources. https://clstr.news/cluster/vitamin-d-functions-sources-and-supplementation-guidelines

### 2026-10-21: Vitamin D deficiency symptoms and absorption factors

Vitamin D is vital for bone and muscle health. Deficiency can cause bone pain and muscle weakness, while absorption is optimized when taken with dietary fats rather than fat-free meals.

2 sources. https://clstr.news/cluster/vitamin-d-deficiency-symptoms-and-absorption-factors

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Cite as: Vitamin D functions and deficiency information. CLSTR, https://clstr.news/situations/vitamin-d-functions-and-deficiency-information