Vitamin D3, also known as cholecalciferol , is a fat-soluble form of vitamin D that is critical for calcium and phosphate metabolism in the body. It contributes to bone health, immune system function, and mood regulation. Vitamin D3 is synthesized in the skin through sunlight and can also be obtained from food or supplements. Because vitamin D3 is not adequately absorbed through sunlight or diet in many countries, deficiency is widespread. In this article, you'll learn why vitamin D3 is important, its benefits, and how to use it safely.
What is vitamin D3?
Vitamin D3 is a form of vitamin D produced in the body when the skin is exposed to UVB rays from the sun. It plays a key role in regulating calcium and phosphate levels in the blood, both of which are important for healthy bones, teeth, and muscles. Vitamin D3 can also be obtained from animal foods such as fish, eggs, and fortified products, as well as from supplements. It is converted into its active form in the liver and kidneys, which then supports various functions in the body [1].
Synonyms for vitamin D3
Vitamin D3 is also known as cholecalciferol , especially in science and supplements. It is one of the two main forms of vitamin D, the other being vitamin D2 (ergocalciferol) . Vitamin D3 is preferred because it is considered more effective at increasing vitamin D levels in the body [2].
Where does vitamin D3 come from?
Vitamin D3 is naturally synthesized in the skin through exposure to sunlight. It is also found in some animal-derived foods, including fatty fish (salmon, mackerel, tuna), cod liver oil, egg yolks, and fortified dairy products. Many people, especially in northern latitudes or areas with low sunlight, have difficulty obtaining sufficient vitamin D3 from sunlight and diet, so supplements are often necessary [3].
How is vitamin D3 produced?
Vitamin D3 in supplements is typically derived from animal sources such as lanolin (wool fat) or fish oil. It can also be produced synthetically to meet human needs. The synthetic form of vitamin D3 is chemically identical to the form produced in the skin and is utilized by the body in the same way. For people seeking a plant-based alternative, vitamin D3 is also available, which is derived from lichens [4].
The different D vitamins: Differences between vitamin D1, D2, D3 and D4
The vitamin D family includes several variants, the most important of which are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D2 is predominantly obtained from plant sources such as mushrooms and yeasts and is often found in fortified foods and supplements. However, its effectiveness in raising blood vitamin D levels is somewhat lower than that of D3, which, as described in this article, is particularly important for bone health, the immune system, and mood.
Other variants, such as vitamin D1 , consist of a mixture of compounds and are less biologically active or are no longer considered a standalone vitamin by scientists. Vitamin D4 (22-dihydroergocalciferol) and vitamin D5 (sitocalciferol) have been less researched and are rarely found in nature. However, they potentially exhibit similar, but weaker, effects than D2 and D3. Overall, the D vitamins play an important role in the immune system, cell growth, and various metabolic processes, with D3 being the most potent and easily absorbed form.
Health benefits of vitamin D3
Vitamin D3 and bone health
The most important health benefit of vitamin D3 is its role in regulating calcium and phosphate metabolism, which is essential for maintaining healthy bones and teeth. Vitamin D3 promotes calcium absorption in the intestines and ensures that sufficient calcium is deposited in bones to maintain their strength. Vitamin D3 deficiency can lead to bone diseases such as osteoporosis in adults and rickets in children [5].
Vitamin D3 and the immune system
Vitamin D3 supports the immune system by promoting the activity and maturation of immune cells such as T cells and macrophages, which are necessary for fighting infections. Studies have shown that people with low vitamin D3 levels are more susceptible to respiratory infections and other diseases. Adequate vitamin D3 intake can help strengthen the immune system and reduce the risk of infections, especially during the winter months [6].
Vitamin D3 and mood
Vitamin D3 plays a role in regulating mood and may help reduce the risk of depression. Research suggests that low vitamin D3 levels are associated with an increased risk of mood disorders, including seasonal affective disorder (SAD). Vitamin D3 influences serotonin production in the brain, a neurotransmitter responsible for regulating mood and well-being [7].
Vitamin D3 and heart health
There is evidence that vitamin D3 may play a role in heart health by supporting blood pressure regulation and reducing inflammation in blood vessels. Studies have shown that people with low vitamin D3 levels have an increased risk of high blood pressure, heart attacks, and other cardiovascular diseases. Adequate vitamin D3 intake may help promote heart health and reduce the risk of heart disease [8].
Vitamin D3 and muscle health
Vitamin D3 also supports muscle health by improving muscle function and reducing the risk of muscle weakness and falls. Vitamin D3 deficiency can lead to muscle weakness and pain, which is particularly problematic in older people. Studies have shown that adequate vitamin D3 intake can improve muscle strength and reduce the risk of falls [9].
How does vitamin D3 work in the body?
Vitamin D3 is synthesized in the skin or absorbed through food and then converted to calcidiol in the liver . Calcidiol is then converted in the kidneys into its active form, calcitriol , which then acts throughout the body. Calcitriol regulates calcium and phosphate metabolism and supports the immune system, bone health, and cellular function. Vitamin D3 also acts as a hormone that influences gene expression and controls the function of many cells in the body [10].
Recommended dosage and use of vitamin D3
What is the recommended dosage?
The recommended daily intake (RDA) of vitamin D3 varies depending on age, gender, and lifestyle. A daily dose of 600 to 800 IU (International Units) is generally recommended for adults. People with limited sunlight exposure or at increased risk of deficiency, such as the elderly or those with dark skin, may require higher doses of up to 1,000 to 4,000 IU per day to maintain optimal vitamin D3 levels [11].
When should you take vitamin D3?
Vitamin D3 should ideally be taken with a meal containing fat, as it is fat-soluble and requires fat for proper absorption. It can be taken at any time of day, but some people prefer to take it in the morning to support their natural circadian rhythm. When taking high doses, it is important to regularly monitor intake and, if necessary, have vitamin D3 blood levels tested [12].
Side effects and safety of vitamin D3
Is vitamin D3 safe?
Vitamin D3 is safe and well-tolerated at recommended doses. However, very high doses taken over long periods can cause vitamin D toxicity, which can lead to hypercalcemia (excessively high calcium levels in the blood). Symptoms of hypercalcemia include nausea, vomiting, weakness, and kidney problems. It is recommended to consult a doctor before taking vitamin D3, especially when taking higher doses [13].
What are the side effects of vitamin D3?
Rare side effects of excessive vitamin D3 intake include stomach upset, constipation, fatigue, headaches, and, in the worst cases, kidney stones due to elevated blood calcium levels. It is important not to exceed the recommended dosage and to have regular blood tests to ensure that vitamin D3 levels remain within a healthy range [14].
Vitamin D3 compared to other forms of vitamin D
Vitamin D3 vs. Vitamin D2
Vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) are the two main forms of vitamin D. Both forms increase vitamin D levels in the body, but vitamin D3 is considered more effective because it increases blood levels of vitamin D for a longer time and in a more sustained manner than vitamin D2. For this reason, vitamin D3 is preferred in dietary supplements and for the treatment of vitamin D deficiency [15].
Vitamin D3 vs. Calcium
Vitamin D3 and calcium work closely together to promote bone health. While calcium is the main component of bones and teeth, vitamin D3 helps the body absorb calcium from food and transport it to the bones. A deficiency in vitamin D3 can impair calcium absorption and lead to bone weakness. Therefore, vitamin D3 and calcium are often taken in combination to support bone health [16].
Natural sources of vitamin D3
The main source of vitamin D3 is sunlight, where UVB rays stimulate the production of vitamin D3 in the skin. Natural dietary sources of vitamin D3 are relatively limited, but fatty fish (salmon, mackerel, tuna), cod liver oil, egg yolks, and fortified foods such as milk, orange juice, and cereal products contain significant amounts. To optimize vitamin D3 levels, people who receive little sunlight should use fortified foods or supplements [17].
When exposed to sunlight, it is especially important to adequately protect your skin.
You can find out more about skin health in this article:
Pomegranate – superfood for heart & skin.
Vitamin D3 in dietary supplements
Vitamin D3 is available in various supplement forms, including tablets, capsules, drops, and gummies. It is also available in combination with other nutrients such as calcium, magnesium, and vitamin K2, which support bone health and calcium utilization in the body. Vitamin D3 supplements are particularly useful for people living in regions with low sunlight or who have difficulty getting their daily intake [18].
Final thoughts on vitamin D3
Vitamin D3 is an essential vitamin that plays a key role in bone health, immune system support, and mood regulation. It helps the body absorb calcium and maintain bone density, while reducing the risk of infections and mood disorders. For people who receive little sunlight or have increased needs, vitamin D3 can be a valuable supplement to promote health.