Sources of vitamin D
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Main Sources of Vitamin D: Sunlight, Diet, and Supplements
Vitamin D comes from three main sources: sunlight exposure, dietary intake, and supplements. The skin produces vitamin D when exposed to ultraviolet B (UVB) rays from the sun, which is the primary source for most people, providing up to 90% of the body's needs Aguilar-Shea2021Saraff2015Kechichian2018+2 MORE. Dietary sources and supplements make up the remainder, which is especially important for those with limited sun exposure Benedik2021Khan2022Dominguez2021+1 MORE.
Sunlight Exposure and Skin Synthesis of Vitamin D
Sunlight, specifically UVB radiation, triggers the production of vitamin D in the skin. This process is the most significant natural source of vitamin D for humans Aguilar-Shea2021Saraff2015Kechichian2018+2 MORE. Factors such as skin type, age, clothing, sunscreen use, and geographic location can affect how much vitamin D the skin can produce Janoušek2022Kechichian2018Bikle2020. People who avoid sun exposure or live in areas with limited sunlight are at higher risk of deficiency and may need to rely more on dietary sources or supplements Janoušek2022Kechichian2018.
Dietary Sources of Vitamin D: Animal and Plant Foods
Few foods naturally contain significant amounts of vitamin D. The main dietary sources include:
- Fatty fish (such as salmon, mackerel, and sardines) and fish liver oils, which are among the richest sources Benedik2021Khan2022Dominguez2021+2 MORE.
- Mushrooms, especially those exposed to sunlight or UV light, can provide substantial amounts of vitamin D2 Benedik2021Khan2022Dominguez2021.
- Eggs, cheese, beef liver, and milk contain smaller amounts of vitamin D Benedik2021Khan2022Dominguez2021.
- Some plant-based foods, like reindeer lichen and certain microalgae, also contain vitamin D Benedik2021Khan2022.
- Fortified foods, such as milk, yogurt, breakfast cereals, orange juice, fat spreads, and plant-based beverages, are important sources, especially in populations with low natural intake Benedik2021Khan2022Dominguez2021.
Vitamin D Supplements and Fortification
Because it is difficult to get enough vitamin D from food alone, especially for those with limited sun exposure, supplements and fortified foods are often recommended to help meet daily requirements Benedik2021Khan2022Aguilar-Shea2021+2 MORE. Supplements are available in two main forms: vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) Benedik2021Dominguez2021. Fortified foods can contain either form or the metabolite 25-hydroxy vitamin D .
Conclusion
The main sources of vitamin D are sunlight exposure, a limited range of animal and plant foods, fortified foods, and dietary supplements. Sunlight is the most effective natural source, but many people need to rely on dietary sources and supplements to maintain adequate vitamin D levels, especially if sun exposure is limited or dietary intake is low Benedik2021Khan2022Aguilar-Shea2021+6 MORE.
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Sources of vitamin D for humans.
Vitamin D can be obtained through sun exposure, dietary sources, and supplements, with fortified foods and certain fish, mushrooms, and lichen being rich sources.
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